Getting plant sex wrong (2)

Posted on 30 Jun 2012 by Cecelia Alexander

I’ve been reading Horseshoe Crabs and Velvet Worms by Richard Fortey. Overall, I’ve been finding it enjoyable. However, portions of the book cause me to cringe. Here’s an example near the beginning of chapter two:

These Gondwanan coniferous trees, with their relatively large leaves and bright berries, do have a very special appearance, at least to a European accustomed to pines and firs with their dry-looking cones. A botanist would remind me I should really describe the berries as “fleshy peduncles” because they carry exposed seeds at their tips.

What’s wrong with that? Well, the trees (podocarps in New Zealand, specifically totara, Podocarpus totara and rimu, Dacrydium cupressinum) Fortey is talking about do not have berries. He is apparently aware of this, but the way he presents it suggests that these things really are berries and that describing them as “fleshy peduncles” is some kind of obscure scientific quibbling. It isn’t: “fleshy peduncle” is right, “berry” is wrong. This follows an irritatingly predictable tendency in science writing about plants: present a misleading description as though it were true, restrict the correct information to some kind of afterthought, and don’t explain it enough for readers to actually figure out what’s going on. This both misinforms readers and gives the impression that the situation is hopelessly complex and cannot be understood by anyone who doesn’t have a PhD and a labcoat.

So, OK, here’s what a fleshy peduncle is. In conifers, a peduncle is a stem that bears one or more cones. In this case we’re talking about seed cones, analogous to the seed cones you’d see on pine, spruce, Douglas fir, etc. You know, these things. In the podocarps Fortey is discussing, the seed cones are very small, having one or two small leaves each with a single exposed seed. In these species, the peduncles bearing the seed cones are swollen, fleshy, edible, and look somewhat like berries. Why aren’t they berries? A berry is a kind of fruit. Fruits are found only in flowering plants (not conifers) and instead of leaves with exposed seeds they have carpels. Carpels are leaves that have been folded and fused into little chambers with seeds inside of them, protected from the environment.

That is more complicated than just saying “these trees have berries; well, technically they’re fleshy peduncles”. However, it’s also informative. Authors writing about science should aim to inform readers about science rather than reinforcing misconceptions and presenting science in a dismissive and uninformative manner.

Here’s a similar example from near the end of chapter 3:

Despite their apparent simplicity, Porphyra and Bangia have quite complex life histories. Cells of the “weed” contain only one package of genetic information; they are described as haploid. A second phase in the life history of these seaweeds is called the Conchocelis stage, which makes miniature branching plants, some varieties of which inhabit the borings they make inside seashells. These plants are so different from their “parents” that they were once given the separate generic name, Conchocelis, which is now only retained as a label for one stage in the life cycle. Conchocelis plants are the diploid, or the sexual, stage of the red algae. The leafy stage releases gametes that mate with one another, thereby doubling up the genetic content; this produces spores that can germinate into Conchocelis.

Some of the basic ideas here are correct. However, the definitions of “haploid” and “diploid” are misleading, the processes of fertilization and sporulation are conflated, and describing Conchocelis as “the sexual stage” is incorrect.

First, what does “one package of genetic information” mean? A package of genetic information could refer to a few different things. It could possibly refer to a gene, or a chromosome, or a nucleus. When discussing haploidy and diploidy, we’re talking about chromosomes, which are long strands of DNA, each containing many genes as well as regulatory sequences and non-coding “junk” DNA, bound up with proteins. So why not just say “one chromosome”? This would be less ambiguous, but it would also be wrong. One vs. two chromosomes is not the distinction between haploid and diploid cells. Instead, the distinction is how many copies of each chromosome is present. In a haploid cell, each chromosome present as a single copy. In a diploid cell, chromosomes are present in pairs. We could easily reword the second sentence of this quote to say “Cells of the ‘weed’ contain only one copy of each chromosome; they are haploid.”

Second, Fortey says that “the leafy stage releases gametes that mate with one another, thereby doubling up the genetic content; this produces spores”, which conflates fertilization and spore production. The union of two gametes is fertilization, the process by which we move from haploid cells to diploid cells. The cell produced by fertilization is not a spore, it is a zygote. The diploid zygote then goes through several mitotic cell divisions to produce diploid spores. By suggesting that fertilization produces spores, Fortey is simply skipping this stage of the life cycle and implying that fertilization directly produces spores, which is incorrect.

Third, Fortey describes Conchocelis as “the diploid, or the sexual” stage of Porphyra and Bangia. Sex consists of the production of gametes and their subsequent union in fertilization. The Conchocelis stage is not directly involved in this process: it doesn’t produce gametes and it isn’t produced by fertilization. Instead, the diploid spores mentioned above can grow into the Conchocelis stage, and the Conchocelis stage produces haploid spores by meiosis (Porphyra and Bangia produce multiple types of spores, which is rather odd). The Conchocelis stage is part of the whole life cycle in these algae and the whole life cycle includes sex, but that’s as close as it gets. It’s like describing a human liver as “the sexual stage” in humans. A functional liver is a necessary component of the human life cycle and the human life cycle includes sex, but the liver doesn’t have any direct role in sex.

The life cycles of Porphyra and Bangia are fairly complex and difficult to describe clearly and accurately. Fortey had two good choices here: either don’t bother with it since it’s not really necessary for the narrative of the chapter or go into the detail needed to convey what’s going on. Instead he makes a third, bad choice: discuss the topic briefly, confusingly, and incorrectly. All readers are likely to get from this passage is that something weird and confusing is happening.

That said, Fortey is doing far better at botany than Bernd Heinrich, who in The Trees in My Forest repeatedly refers to “flowers” of conifers. This is just wrong. Pines do not have flowers. At least Fortey tells us that the “berries” of podocarps are in fact fleshy peduncles, even if he does so in a rather unhelpful fashion. And maybe we can cut him some slack, since his book isn’t primarily focused on plants, much less trees or conifers in particular. Heinrich, on the other hand, wrote a book about trees, with long discussions of conifers, and gets it completely wrong. He tells us that conifers have flowers and provides no explanation nor any indication that this might not be consistent with what we actually know about botany.

Geranium dodecatheoides

Posted on 20 Dec 2011 by Cecelia Alexander

My second new species from New Mexico is published, Geranium dodecatheoides P.J.Alexander & Aedo. Many thanks to Carlos Aedo, who knows far more about Geranium than I could ever hope to. Read the article here: http://www.bioone.org/toc/rhod/113/955. The location where I found it happens to be along one of the most readily accessible trails in the Sierra Blanca; it is surprising that it has not been collected before, but so far as I can tell it was completely overlooked. So, one more reason to keep your eyes open outside, even in areas where you wouldn’t really expect to find anything too exciting. I’m sure I’ve stumbled past at least as many undescribed species as I’ve happened to notice… with luck, perhaps I’ll find another that I can give a name with even more syllables!

Botany is hard

Posted on 1 Dec 2011 by Cecelia Alexander

So, in the post below, and probably in a number of posts that will follow, I criticize the results of or approaches to research that relies on field botany and plant identification. I should say now: it’s hard. None of us always get it right and mistakes will be made. A major target of my ire tends not to be that people aren’t perfect botanists, but that I think there is a systematic undervaluation of botanical expertise. Field personnel whose work requires them to be able to identify plants are often poorly trained and poorly paid, because the difficulty of the work is not appreciated. So far as I can tell, land management agencies and ecological research stations assume that someone who’s taken a couple of courses in plant taxonomy can be sent into the field and will bring back reliable data. Well, I’ve taken those courses, I’ve taught those courses, I’ve botanized extensively across much of the western United States, and I can tell you (assuming, hypothetically, a reader) now: this simply is not the case.

Someone who’s taken the courses available at NMSU (Rangeland Plants, Rangeland Grasses, Plant Taxonomy), done well and studied conscientiously, should be able to sight-ID a fair number of the common species (but few of those uncommon species that make up most of the biodiversity), and should be able to key out most plants assuming there is flowering and/or fruiting material available (and there often isn’t, but field crews don’t tend to have the luxury of waiting for good conditions). But that’s it. Don’t expect or rely on sight-IDs of most of the plants in the area, and don’t expect that any kind of identification will be possible for most species if the plants are in poor shape and many or most of the diagnostic characters are absent.

Suppose you want to answer a simple question: is plant diversity higher in grasslands or shrublands in southern New Mexico? Well, if you want reliable data, you need a field crew of people who already have several years of experience–probably voluntary / recreational since, AFAICT, no one will pay you to learn plants–botanizing in the area. Those people are scarce, and most of them have Masters or PhD degrees (and many are retired!); you probably can’t (and, ethically, shouldn’t) hire them for crappy minimum or near-minimum wage temporary positions. If, on the other hand, you hire a field crew of people fresh from their undergrad degrees whose experience is limited to two or three courses in plant ID or taxonomy, either that crew is going to be spending 90% of its time learning plant ID, or you’re going to get crappy, unreliable data. (As for the simple question, so far as I know there is no reliable answer! More on that some time later.)

One way to minimize the expertise required is to only focus on a few of the dominant plant species (as in the vegetation maps discussed in the post below). It is better to recognize one’s limitations and work within them, but this approach means you’re ignoring most of the botanical diversity in the area… not exactly ideal, in my opinion.

The gist is, if you try to fill botanical field crews on the cheap, rather than hiring highly trained botanists with extensive experience, you have a few options, none of them particularly good: deal with poor accuracy of identifications; get very little data back because your field crews are spending most of their time learning the plants; adopt a very myopic view of plant communities.

Floral inventory of my apartment

Posted on 1 Dec 2011 by Cecelia Alexander

An inventory of the plants presently living in my apartment. Some identifications are very approximate, as a number of these were acquired through greenhouses that don’t label plants and so forth… and I don’t exactly have, say, a key to all the species of Aechmea, Neoregelia, all the myriad cultivated varieties in genera like Saintpaulia, etc. Listed in alphabetical order by family, genus, then species.

Asteraceae:

Senecio articulatus
Senecio stapeliiformis

Bromeliaceae (I have a particular fondness for terrestrial bromeliads, as you may notice):

Acanthostachys pitcairnoides
Acanthostachys strobilacea
Aechmea sp. (not one of the obnoxious cultivars; alas, I’ve lost the tag indicating which species)
Billbergia chiapensis
Billbergia zebrina (thought this thing was dead for a good while!)
Deuterocohnia brevifolia
Dyckia platyphylla
Fosterella kroemeri (or perhaps F. windischii; I need to wait for flowers to tell; sold to me as Fosterella albicans)
Fosterella latifolia (sold as Fosterella villosula; Fosterella latifolia is placed in synonymy of Fosterella penduliflora in a revision by Jule Peters but it looks different so, what the hell, I’ll list it separately)
Fosterella penduliflora (I’ve had these for something like 15 years; they reseed readily and are hard to kill)
Fosterella petiolata (I think)
Fosterella spectabilis
Neoregelia sp. (not one of the obnoxious cultivars; alas, I’ve lost the tag indicating which species)
Orthophytum saxicola
Pitcairnia cf. punicea

Cactaceae (I don’t particularly like cacti, but somehow I end up with them anyways!):

x Disophyllum, unknown cultivar
Echinops, unknown hybrid
Mammillaria elongata
Mammillaria hernandesi
Rhipsalis baccifera
Rhipsalis paradoxa
Schlumbergera, unknown cultivar (white flowers)
Stenocactus zacatecasensis

Commelinaceae:

Tradescantia spathacea

Crassulaceae:

Sedum wrightii

Euphorbiaceae:

Euphorbia horrida
Euphorbia obesa (although it doesn’t look particularly happy…)

Gesneriaceae:

Saintpaulia, unknown cultivar (single purple flowers)

Hypnaceae:

Hypnum sp.

Isoëtaceae:

Isoëtes louisianensis
Isoëtes melanopoda

Marchantiaceae:

Marchantia polymorpha

Marsileaceae:

Marsilea vestita

Moraceae:

Dorstenia foetida
Ficus sansibarica

mosses (unknown family):

several species that I have not identified

Ophioglossaceae:

Botrychium lunarioides
Ophioglossum crotalophoroides

Polypodiaceae:

Davallia sp.

Polytrichaceae:

Atrichum sp.
Polytrichum sp.

Porellaceae:

Porella sp.

Psilotaceae:

Psilotum nudum

Pteridaceae:

Astrolepis sinuata (it volunteered in a terrarium, of all things)
Astrolepis windhamii
Bommeria hispida
Cheilanthes eatonii
Cheilanthes fendleri
Cheilanthes lindheimeri
Cheilanthes yavapensis
Pellaea atropurpurea
Pellaea gastonyi
Pellaea truncata
Pellaea wrightiana
Pteris cretica

Selaginellaceae:

Selaginella erythropoda
Selaginella moellendorfii
Selaginella rupincola

Sphagnaceae:

Sphagnum sp. (not really sure why I bought this… online biological supply stores are dangerous)

Vitaceae:

Cissus quadrangularis

Welwitschiaceae:

Welwitschia mirabilis

Xanthorrhoeaceae:

Haworthia herbacea

[updated 30 Jan 2014]

Plant diversity in New Mexico

Posted on 28 Nov 2011 by Cecelia Alexander

From 14 Oct 2010.

Out of curiosity, I decided to find out how many taxa (species + varieties or subspecies as applicable) are recorded from each of the counties of New Mexico. I searched the herbarium records at swbiodiversity.org & ran the results through the ASU taxonomic database, which will keep the same taxon from showing up multiple times if it’s listed under several synonyms. Of course, the taxonomic filter only works if the ASU database contains the appropriate names and synonymies; generally speaking it probably does, but there are certainly omissions and errors as well. There’s also some error in specimens being recorded for the wrong county due either to error when databasing, the collector not really knowing where he or she was, or changing county boundaries. So, the numbers are quite approximate but as good as can be done without devoting considerable time to the project. That said, here are the results on a map:

Now, one reason for doing this is that I had heard, from Dr. Heil at San Juan College, that Rio Arriba was the most diverse county in the state botanically. I was skeptical, but didn’t really know any better, but now I at least have some basis to believe otherwise; Grant County appears to be most diverse, with Rio Arriba in seventh. My initial guess was that Doña Ana or Hidalgo County would come out on top; with Doña Ana in third I guess that’s not bad, though Hidalgo’s a bit further down. Differing results between myself and Dr. Heil may be due to his use of the NMBCC (New Mexico Biodiversity Consortium) database at nmbcc.org; this database includes only the holdings of New Mexico herbaria, while swbiodiversity.org includes New Mexico holdings from the Arizona herbaria and a few others.

It’s also worth mentioning that there are some obvious biases in collecting. The eastern counties, in particular, are poorly collected. However, this alone is unlikely to account for their low diversity. For instance, there have been at least one or two floristic inventory projects in Roosevelt County (including a flora of Milnesands by Rob Strahan), and so it has about twice as many species recorded from it as most of the surrounding counties. However, the total of 651 is still unimpressive.

Getting plant sex wrong

Posted on 28 Nov 2011 by Cecelia Alexander

From 28 Oct 2009.

Watching “Botany of Desire” on PBS. I’ve generally been a bit ambivalent about Michael Pollan, but about 36 minutes in he veers into “just plain wrong” territory. “Before that [before the evolution of angiosperms] you had this greener, sleepier world where things reproduce usually by cloning, by spores that were genetically identical to their parents”. Regarding cloning–yes, there were a fair number of clonal plants before angiosperms evolved, but there are also plenty of clonal angiosperms. Regarding spores–he is right that sexual recombination isn’t involved in producing spores but: 1) this does not mean the spores are genetically identical to the parent–they aren’t; 2) angiosperm reproduction involves the production of spores as well, so this is not a difference between angiosperms & non-angiosperms.

Brief recap of plant life cycles: the dominant portion of the vascular plant life cycle is the sporophyte (on the other hand, gametophytes are dominant in non-vascular plants: mosses, liverworts, hornworts), which is diploid (has two sets of chromosomes, just like all stages of the human life cycle except sperm & eggs). The diploid sporophyte produces spores by meiosis. Meiosis halves the chromosome number, so the spores are haploid. Whereas the sporophyte has two copies of each gene (excluding the rare cases in which plants have sex chromosomes), each spore has one copy of each gene. It’s the same as the relationship between, for instance, a human male and one of his sperm cells (except, for the sake of nit-picking, that humans have sex chromosomes and most plants don’t), and is not genetic identity. However, whereas human sperm & egg cells do nothing more than unite to form a zygote, plant spores undergo cell divisions to produce gametophytes. Gametophytes are a multicellular haploid stage in a vascular plant’s life cycle, and they produce gametes (sperm and eggs) through mitosis. Gametophytes exist in all plants, but are quite small and dependent on the sporophytes in angiosperms. Pollen grains are male gametophytes. Inside each ovule lives a female gametophyte. When the sperm and eggs produced by gametophytes join in fertilization, we are back at the diploid sporophyte level. Very short version: diploid sporophyte produces spores; spores grow into haploid gametophyes; gametophytes produce sperm & eggs; fertilization takes us back to a diploid sporophyte. Although (with minor exceptions; e.g., the genus Vittaria, some species of which exist solely as gametophytes) all plants produce spores, in no plants is the production of spores itself sexual. The production of spores is part of the sexual process, however; without the gametophytes they give rise to, you can’t get gametes. Lest you think Pollan just misplaced a word or two, he continues: “And then you have this incredible explosion of diversity that happens with this new strategy. It was an incredibly successful strategy. It allowed you [by which he means angiosperms] to move your genes around, it allowed you to evolve much quicker because sex creates variation.” Nope, he didn’t just misplace a word or two, he’s really saying that the key innovation of angiosperms relative to earlier plants was sex.

Eryngium

Posted on 28 Nov 2011 by Cecelia Alexander

From 7 Oct 2007

How to distinguish Eryngium heterophyllum and Eryngium lemmoni
or
Why I don’t like to use the Kearney & Peebles Flora of Arizona

Here is how Kearney & Peebles distinguish these two species:
“3. Plants from a cylindric taproot; lower cauline leaves pinnatifid to bipinnatisect; inflorescence paniculately branched, the heads comate; bracts linear-lanceolate to lanceolate, entire or with 1 or 2 pairs of lateral spines near the middle, commonly yellowish above . . . . . . . 3. E. heterophyllum
3. Plants from a fascicle of fibrous or fleshy roots; lower cauline leaves spinose-serrate; inflorescence successively trifurcate, the heads not comate; bracts broadly lanceolate to oblanceolate, spinose-serrate with 2 or 3 pairs of teeth, silvery-white above . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. E. Lemmoni”

And here are my observations on the various characters:
“Plants from a cylindric taproot” vs. “plants from a fascicle of fibrous or fleshy roots”. This appears to be accurate and, although not necessarily a useful field character, this can be a useful distinction with good herbarium specimens.
“Lower cauline leaves pinnatifid to bipinnatisect” vs. “lower cauline leaves spinose-serrate”. This is also essentially accurate, although it could be better worded, for instance by including a more quantifiable distinction rather than descriptive terms that can be somewhat subjective (how deep must the divisions be before the leaf is pinnatifid?).
“Inflorescence paniculately branched” vs. “inflorescence successively trifurcate”. This is simply inaccurate. Inflorescences of the two species are quite similar. In both, as we move up the plant we have first several alternately arranged primary inflorescence branches, then a whorl of ca. 3-7 primary branches. Each primary branch of the inflorescence is determinate, and may either terminate in 2-3 heads arising from a single node, or the lateral head(s) may be replaced by secondary branches terminating in groups of 2-3 heads. It seems to be more common for E. heterophyllum to have the terminal groups with only 2 heads, and E. lemmoni to have groups of 3 heads. However, this is by no means a uniformly applicable identifying characteristic, and neither species has an inflorescence that is accurately characterized as “paniculately branched” or as “successively trifurcate”, although the primary branches of the inflorescences of either species may (or may not) be “successively trifurcate”.
“The heads comate” vs. “the heads not comate”. “Comate” is, first, a needlessly obscure term. I do not recall having heard it before, in any context, and although it sounds much like the more commonly used “comose” the meaning is quite different. In any case, a comate head is one in which the bracts of the head are greatly enlarged at the apex of the head and form a leafy projection beyond the flowers. Pineapples are comate. The heads of E. lemmoni are indeed not comate and most heads on most specimens of E. heterophyllum are indeed comate. But some heads on many specimens, and all heads on rare specimens of E. heterophyllum are not comate, or at best indistinctly so. So this is a one-directional character; plants with comate heads must be E. heterophyllum, but plants with non-comate heads could be either species.
“Bracts linear-lanceolate to lanceolate, entire or with 1 or 2 pairs of lateral spines near the middle” vs. “bracts broadly lanceolate to oblanceolate, spinose-serrate with 2 or 3 pairs of teeth”. This is accurate, although unfortunately there is overlap in the descriptions.
Bracts “commonly yellowish above” vs. “silvery-white above”. I cannot tell if this character is inaccurate, or simply variable and of limited utility. I have only seen E. heterophyllum in the field at two locations (Rucker Canyon in the Chiricahua Mts. and Clanton Draw in the Peloncillo Mts.), but both times the bracts were silvery-white above. No difference in bract coloration is apparent from the herbarium specimens I looked at earlier today, but colors are often unreliable in dried material. Presumably any specimens that did clearly have yellowish bracts could be readily identified but, as with non-comate heads, specimens with silvery-white bracts (which appear to be the overwhelming majority) could be either species.

Although this is the most annoying example I have encountered recently (since this key has resulted in my misidentifying E. heterophyllum as E. lemmoni not once but twice), it is unfortunately not an isolated example. Most keys in the Kearney & Peebles flora are well written and eminently usable. However, a significant minority are not, and while these keys will still usually yield correct identifications if used carefully while comparing specimens of all of the relevant taxa, they often make me feel rather confused and can easily lead to misidentifications if used incautiously.

Plants in washing machines

Posted on 28 Nov 2011 by Cecelia Alexander

I’ve put compact flash cards through the wash a few times with no ill effect, but I discovered a stem of Senecio pendulus that had made it through the washing machine. This is a succulent species, with jointed stems and no leaves, similar in some ways to Cylindropuntia (but without spines). The joints break off readily, and one apparently fell among my dirty laundry. In any case, it is apparently no worse for wear and I’ve planted it. We’ll see if it survives.

Quotes from Stebbins

Posted on 28 Nov 2011 by Cecelia Alexander

A collection of edifying (or, at least, interesting to me) quotations from G.L. Stebbins’ Variation and Evolution in Plants, originally posted in Sep 2006.

p. 1:
“The hierarchy of categories is a multidimensional pattern of variation in nature, and the gaps or discontinuities give reality to the various categories.”

I think (and hope) he means taxa by “categories”. This seems to be his usage elsewhere. There are several other interesting quotes in the first few dozen pages that I may put up later.

p. 34:
“All [Dobzhansky, Mayr, & Huxley] agree that species must consist of systems of populations that are separated from each other by complete or at least sharp discontinuities in the variation pattern, and that these discontinuities must have a genetic basis.”

This remains essentially the case with modern disagreements on species concepts. The disagreements are not in what species are, but in what is the best axis on which to look for discontinuities.

p. 35:
“In fact, it is likely that most families in which the genera are well-defined have suffered the extinction of many species, and further that most boundaries between neighboring genera represent gaps left by species which have perished.”

The importance of extinction in observed patterns remains often overlooked and misunderstood. In most cases monophyletic taxa, for instance, were probably previously paraphyletic groups in which sufficient lineages have subsequently become extinct.

Stebbins continues:
“If this fact is kept in mind, then the search for natural boundaries to genera has some meaning to the evolutionist and is not entirely a matter of convenience.”

pp. 189-190:

“The common ground of agreement between these definitions may be expressed as follows. In sexually reproducing organisms, a species is a system consisting of one or more genetically, morphologically, and physiological different kinds of organisms which possess an essential continuity maintained y the similarity of genes or the more or less free interchange of genes between its members. Species are separated from each other by gaps of genetic discontinuity in morphological and physiological characteristics which are maintained by the absence or rarity of gene interchange between members of different species. The above sentences are not to be construed as this authors definition of a species, since several different species definitions are possible within the framework of their meaning.”

But–isn’t it precisely the problem of existing species concepts that they try to limit us to a single axis for discerning species, rather than admitting of several different axes, as Stebbins’ sentences above do? Why not embrace such a broad and inclusive definition–merely because it could be subdivided?

p. 202:
“The second alternative [the first was multiple species concepts] would be to recognize that at any given moment in the evolutionary time sale, reproductive isolation is important in keeping distinct only those populations which are sympatric or which overlap in their distributions.”

In other words… Mayr’s Biological Species Concept is applicable only to sympatric or overlapping populations. This criticism has been hemmed and hawed over for five decades now, but has never been addressed in a coherent fashion. And it is precisely a multidimensional species concept that will allow us to overcome this problem, as well as those that plague the other species concepts. Why, after all, would we expect groups in multi-dimensional space to always be identifiable along a single axis, like that of reproductive isolation?

More bits of Stebbins; p. 262:

“Hybridization between well-established and well-adapted species in a stable environment will have no significant outcome or will be detrimental to the species populations. But if the crossing occurs under rapidly changing conditions or in a region which offers new habitats to the segregating offspring, many of these segregates may survive and contribute to a greater or lesser degree to the evolutionary progress of the group concerned.”

p. 270:

“There is little doubt, therefore, that the majority of the examples of hybridization and introgression which can be found in plant populations at the present time are associate with the disturbance of old habitats and the opening up of new ones through human activity.”

Thysanocarpus diagnoses

Posted on 28 Nov 2011 by Cecelia Alexander

I figure I’ll put some of the more interesting (to me, at least), articles from the old pseudo-blog on here as well. So, from 1 Nov 2008:

An entry for my own reference so much as anything else, descriptions of the various species, subspecies, and varieties named in the mustard genus Thysanocarpus, in alphabetical order. Only basionyms of taxa presently included in Thysanocarpus (i.e., no Athysanus) are listed.

First, the description of the genus by Hooker, 1829, Flora Boreali-Americana 1: 69.
29. THYSANOCARPUS. Nov. Gen.
Silicula obovata, plano-convexa, undique latissime marginato-alata, apice emarginata, unilocularis, evalvis, monosperma. Semen late obovatum, pendulum. Radicula inserticae dorsalis, obliqua et ad margines cotyledonum applicata.–Flores parvi, albi, racemosi. Siliculae pendulae.–Genus Tauscheriae affinis. An vere distinctum?

Thysanocarpus affinis Greene, 1901, Pittonia 4: 311-312.
Thysanocarpus affinis. Very erect, 1 to 1 1/2 feet high, simple below, parted above the middle into several suberect racemose branches; herbage glabrous, glaucous: lowest leaves not seen, the larger cauline 3 inches long, of narrow-lanceolate outline, with several pairs of very prominent subulate or often falcate-incurved teeth, the base slightly auricled, those of the flowering branches lance-linear, very saliently denticulate: petals very small, not exceeding the sepals, but stamens well exserted: silicles of strongly pyriform outline, small, unevenly crenate, never perforate, the scarious margin very narrow or obsolete, the whole body of silicle hirtellous.
Santa Catalina Island, California, March, 1901, Blanche Trask. The species has the foliage of T. ramosus of the same island and of others of the group, but in mode of growth this plant is at the opposite extreme, while the characters of the pods are very distinctive.

Thysanocarpus amplectens. Stem stoutish, simple and leafy below, with a few racemose branches at the middle, 12 to 20 inches high, glabrous throughout and very glaucous: lowest leaves unknown; cauline linear-lanceolate, remotely and retrorsely dentate, with very conspicuous sagittate lobes at base which clasp the stem: white petals shorter than the purple (white-margined) sepals; stamens scarcely exserted: pod nearly orbicular, glabrous, the body reticulate-venulose, the wing of 14 to 16 short rays and a regularly crenate hyaline margin, but no perforations.
Type collected by the writer in southwestern New Mexico, 16 April, 1880; referred by Asa Gray at the time to T. elegans, from which species its perfectly glabrous and strongly glaucous herbage effectually excludes it. It is really of the group to which T. laciniatus belongs, though its very conspicuously sagittate-clasping and merely dentate leaves, as well as its mode of growth, prevent its being confused with that species. I do not know how much of the Thysanocarpus materials from Arizona now extant in herbaria may be referable to this very distinct extra-Californian member of the genus.

Thysanocarpus conchuliferus Greene, 1886, Bulletin of the Torrey Botanical Club 13: 218.
Thysanocarpus conchuliferus.–Glabrous, 3–7 inches high, with many divergent branches; leaves linear, the lower cleft into narrow segments, the cauline auricled at base; racemes short and rather close; pods a line or more in length, cymbiform, the conduplicate margin sinuately parted into spatulate divisions, or the latter coherent above, leaving narrowly oblong perforations; style equalling the margin of the pod and commonly coherent with it; pedicels nearly divaricate or quite straight, twice as long as the pods; flowers not seen.
Common on mossy shelves and crevices of the high rocky summits and northward slopes of Santa Cruz Island. A most interesting new species, very remarkable in the character of its fruit; showing how nearly our American Thysanocarpus can approach the Asiatic genus Tauscheria and yet remain a perfectly valid genus, the very dissimilar Athysanus being excluded.

Thysanocarpus conchuliferus Greene var. planiusculus B.L.Rob., 1896, Synoptic Flora of North America 1(1): 113.
Var. planiusculus, Robinson, n. var. Fruit plano-convex or slightly concavo-convex, not perceptibly reticulated but hirsute upon both sides: pedicels 4 to 6 lines long.–Island of Santa Cruz with type, T. S. Brandegee, April, 1888.

Thysanocarpus crenatus Nutt. ex Torr. & A.Gray, 1838, A Flora of North America 1: 118.
4. T. crenatus (Nutt.! mss.): “petals about as long as the calyx; silicles orbicular-obovate, crenate, glabrous, slightly emarginate, membranaceously winged; the wing perforated; style not exserted; leaves linear-lanceolate, runcinately and remotely denticulate.
“St. Barbara, California, March–April.–Stem 12-14 inches high, branching above. Leaves an inch long; the lower ones somewhat hirsute. Silicles about half as large as in T. curvipes; the wing more or less perforated.” Nutt.

Thysanocarpus curvipes Hook., 1829, Flora Boreali-Americana 1: 69-70.
1. T. curvipes. (Tab. XVIII. A.)
Radix parva, annua, subfusiformis. Caulis solitarius, plerumque ramosus, erectus, 6-8-pollicaris ad pedalem, parce foliosus, inferne subpilosus. Folia plerumque radicalia, patentia, duas uncias longa, pinnatifida, hirsuto-scabra, laciniis brevibus, obtusis, basi attenuata. Caulinea remota, linear-oblonga, basi latiora, subsagittata, superiora sensim minora. Flores racemosi, parvi, ramos terminantes. Pedicelli floribus paululum longiores, graciles, glaberrimi, patentes, demum, fructiferi, insiguiter deflexi et elongati. Calyx: sepala aequalia, ovalia, convexa, glabra, erecto-patula. Petala minuta, lineari-oblonga, basi attenuata, integra, alba, sepalis breviora. Stamina 6, tetradynama: Filamenta filiformia, edentula: Antherae subglobosae. Germen brevissime stipitatum, obovatum, plano-compressum, lato-marginatum, alatum, apice emarginatum, stylo subaeque longo, demum, et videtur, deciduo teminatum. Stigma obtusum, parvum. Silicula dependeus, forma et structura fere omuino alatum, apice emarginatum, stylo subaeque longo, demum, et videtur, deciduo teminatum. Stigma obtusum, parvum. Silicula dependeus, forma et structura fere omuino germinis, sed estylosa, convexo-plana, utrinque subreticulata, vix uninervis, unlocularis, evalvix. Embryo flabus. Cotyledones suborbiculatae, plano-convexae: Radicula subaeque longa, insertione evidentissime dorsalis, sed obliqua et versus margines cotyledonum incumbens.
Hab. On moist ground, near the Great Falls of the Columbia. Fl. April, May. Douglas–I long hesitated whether or not I should unite this interesting plant with the genus Tauscheria of Dr. Fischer, with which it sufficiently accords in habit, and, in many respects, in the singular structure of the seed-vessel. In both the species of Tauscheria, however, of which I have excellent specimens from Dr. Fischer and Professor Ledebour, the silicula is truly cymbiform, the margin is curved inwards, and the extremity, instead of being broad and notched, as in Thysanocarpus, is narrow and elongated into a beak, like the narrow prow of a vessel. Its perfect embryo I have not been able to examine: but in our plant, this has always its radicle inserted at the back of one of the cotyledons, and then inclines obliquely, so that the greater part of its length is applied to the edge or margin of the cotyledons. In the figure here given, the seed did not occupy the whole of the cavity of the cell, as was the case with more fully ripe capsules, given to me by Mr. Douglas after the plate was engraved, and which, I believe, were produced by plants cultivated in the Garden of the Horticultural Society.
[note–my .pdf of Flora Boreali-Americana is at times difficult to read; the Latin probably has typos.]

Thysanocarpus curvipes Hook. var. cognatus Jepson, 1936, A Flora of California 2: 100.
Var. cognatus Jepson var. n. Herbage nearly glabrous, a little glaucous; blades of cauline leaves entire or nearly so; pods orbicular-elliptic, abruptly contracted to a shortly cuneate base, 3 lines long, not notched at apex or only slightly.–(Fere glaber, glauciusculus; folia caulina subintegerrima integerrimave; siliquae orbiculato-ellipticae, base breviter cuneata (lin. 3 longa) abrupte contractae, ad apicem fere integerrimae.)–Pine Log, South Fork Stanislaus River, A. L. Grant 702 (type); Lake Eleanor, Tuolumne Co., 4690 feet, A. L. Grant 1257.

Thysanocarpus curvipes Hook. var. eradiatus Jepson, 1925, A Manual of the Flowering Plants of California: 447.
1. T. curvipes Hook. Fringe-pod. Fig. 438. Slender, 1 to 1 1/2 ft. high, more or less pubescent or hirsute; cauline leaves linear or lanceolate, the lower dentate or denticulate; basal leaves often
narrowed at base to a petiole, commonly sinuate-pinnatifid, with triangular acute or acuminate lobes; pods obovate varying to round-obovate, pubescent or glabrous, 1 1/2 to 3 1/2 lines long, often very convex on one side; wing narrow, rather crowded with broad rays, entire.–Frequent in the open hill country of Cal., 100 to 5000 ft.: n to B. C. and Ida. Var. eradiatus Jepson n. var. Wing of pod membranous, without rays.–Deserts, Inyo Co. (Panamint Range, Jepson 7040, type) s. to the Colorado Desert.

Thysanocarpus curvipes Hook. var. involutus Greene, 1891, Flora Franciscana: 276.
1. T. curvipes, Hook. Fl. i. 69. t. 18 (1829): T. runcinatus, Hook.: Don. Dict. i. 196 (1831). A foot high or more, with few and rather strict racemose branches, or smaller and simple-stemmed; radical leaves in a rosulate tuft, pinnatifid, with short obtuse lobes or subentire, hirsute; cauline oblong- or linear-lanceolate, entire, sagittate-clasping: fr. obovate, seldom 2 lines wide, strongly concavo-convex, glabrous or slightly tomentose, the marginal rays broad, dilated above, rather crowded, with narrow diaphanous spots (rarely a few perforations) between them. Var. (1) involutus. Taller and more strict: fr. elliptical, only a line wide; rays nearly obsolete, the purplish subscarious margin closely involute all around; style (rather prominent in fl.) deciduous. Var. (2) pulchellus. T. pulchellus, F. & M. (1835). Radical leaves merely toothed: pods densely tomentose; the wing rather broader.–The type of this species has not been found south of Mt. Shasta, except in Humboldt Co., Marshall, Miss Bush. The first variety is from Sonoma Co.,
Bioletti, and this may not improbably be found distinct. Var. 2 is our most common form in middle Calfornia.

Thysanocarpus curvipes Hook. var. longistylus Jepson, 1925, A Manual of the Flowering Plants of California: 447.
1. T. curvipes Hook. Fringe-pod. Fig. 438. Slender, 1 to 1 1/2 ft. high, more or less pubescent or hirsute; cauline leaves linear or lanceolate, the lower dentate or denticulate; baasl leaves often narrowed at base to a petiole, commonly sinuate-pinnatifid, with triangular acute or acuminate lobes; pods obovate varying to round-obovate, pubescent or glabrous, 1 1/2 to 3 1/2 lines long, often very convex on one side; wing narrow, rather crowded with broad rays, entire.–Frequent in the open hill country of Cal., 100 to 5000 ft.: n to B. C. and Ida. […] Var. longistylus Jepson n. var. Style 1/2 to 3/4 line long (in the species 1/8 to 1/5 line long), persistent.–Sierra Nevada, 3000 to 3500 ft., from Mariposa Co. to Tulare Co. (Jepson, type).

Thysanocarpus curvipes Hook. subsp. madocarpus Piper, 1906, Flora of Washington. Contributions from the United States National Herbarium 11: 306.
1a. Thysanocarpus curvipes madocarpus subsp. nov.
Differs from the species in having its pods glabrous instead of puberulent.
From field observations this seems worthy of subspecific rank. While both forms may occur close together, yet so far as my observations go a particular colony of plants is of one form of the other; the two do not occur mixed.

Thysanocarpus deppii Nutt. ex Torr. & A.Gray, 1838, A Flora of North America 1: 118.
2. T. elegans (Fisch. & Meyer): petals nearly twice as long as the calyx; silicles orbicular-obovate, membranaceously winged; the wing (often) perforated with holes, emarginate at the apex.
a. silicles glabrous; style conspicuously exserted.–T. elegans, Fisch. & Meyer, l.c.
b. silicles villous; style slightly exserted. Hook.! ic. t. 39. T. Deppii, Nutt. mss. T. n. sp. Fisch. & Mey. l.c. (without a name.)
g. silicles somewhat pubescent, wing not perforated; style not exserted.
California, Douglas! Deppe. (ex Fisch. & Meyer.)–Stem 12-18 inches high, branching, nearly glabrous, Leaves in b. lanceolate, sagittate, repandly toothed; in g. linear, the upper ones almost subulate and sagittate-clasping. Silicles 2 1/2 lines long; the winged margin perforated with a row of 12-14 oblong holes, or marked with thin diaphanous spots, the opaque coriaceous substance of the centre extending between them, and thus giving the silicle a radiated appearance.

Thysanocarpus desertorum A.Heller, 1905, Muhlenbergia 2: 47.
Thysanocarpus desertorum Glabrous, yellowish, especially in the inflorescence, maximum height 2 dm, branched from the base, the branches ascending, becoming somewhat racemose: leaves scattered, the lowest ones oblanceolate, about 3 cm. long, 4 or 5 mm. wide, sparingly runcinate-dentate, acute or acutish; those above smaller, nearly linear, not narrowed at the base, clasping but not auricled: pedicels 3 mm. long or less: flowers very small, the sepals obovate-oblong, white or yellowish with broad green midvein: petals a little shorter and narrower than the sepals: silicle plane or nearly so, orbicular, 3 mm. across, slightly reticulated, glabrous, minutely crenate but not perforate; the short style not exserted from the notch.
The type is no. 7681, collected April 14, 1905, on rocky hilltops near Randsburg, Kern County, growing under overhanging rocks.

Thysanocarpus elegans Fisch. & C.A.Mey., 1835, Index Seminum, quae Hortus Botanicus Imperialis Petropolitanus pro Mutua Commutatione Offert. Accedunt Animadversiones Botanicae Nonnullae 2: 51.
Th. elegans F. et M. Th. petalis calyce longioribus; siliculis glaberrimis ala foraminosa cinctis apice truncatis styloque exserto terminatis.–A Th. pulchello, quocum crescit et cui ceterum persimilis est, silicularum ala foraminibus numerosis latis uniseriatus pertusa facile dignoseitur.
[Exceedingly approximate translation: “Petals longer than the calyx; silique smooth and with perforate wings, apex truncate with the style much exserted terminally.–Similar to Thysanocarpus pulchellus, but the perforate wings of the siliques readily distinguish it.” Quoting from Jeremiah Johnson: “Now isn’t that easier than saying all that gibberish?”]

Thysanocarpus emarginatus Greene, 1896, Pittonia 3: 86-87.
Thysanocarpus emarginatus. Slender and low, much branched from the base, glaucous and also hispidulous, with scattered, spreading or deflexed white bristly hairs: cauline leaves all linear-lanceolate, entire, sessile but in no degree auricled or even dilated at base: flowers and radical leaves unknown: pedicels of fruit short, spreading, scarcely curved: fruit nearly orbicular, the body glabrous, with strong midvein and almost equally prominent transverse veinlets, the broad wing perfectly entire, scarious, abruptly and rather deeply emarginate at apex, wholly destitute of perforations and lacking even the usual radiating bundles of fibrous tissue.
Collected by the writer at the summit of Mt. Diablo, Calif., 20 June, 1892, and very erroneously referred, at the time, to T. laciniatus; from which it is distinguished not so definitely by its pubescence as by the remarkable character of the pods. In the structure of the wing of the fruit this species is equally removed from the group of the original species and from T. radians; but it has an ally in T. Palmeri of the far-distant Cedros Island.
[There is no species named Thysanocarpus palmeri; perhaps Greene was referring to Thysanocarpus erectus, see below.]

Thysanocarpus erectus S.Wats., 1876, Proceedings of the American Academy of Arts & Sciences 11: 124.
Thysanocarpus erectus. Smooth and leafy: leaves oblong to oblanceolate, an inch or two long, auricled at base, somewhat sinuate-dentate: flowers purple or rose-colored: fruiting pedicels erect: pod minutely pubescent, the wing of the fruit (still immature) without indication of nervation or perforation: style very short — Collected by Dr. E. Palmer on the western side of Guadalupe Island. Distinguished especially by its erect pedicels.

Thysanocarpus filipes Greene, 1900, Pittonia 4: 200-201.
Thysanocarpus filipes. Slender, branched from near the base and all the branches racemose: herbage scarcely glaucescent, deep-green: leaves of the stem (the lowest not seen) lanceolate, acuminate, sessile by a subhastate base: racemes dense: pods round-obvate, 1/4 inch long, on filiform pedicels of 1/4 to 1/2 inch, the whole body of the fruit very minutely hirtellous, only obscurely venulose, the rays about 12, for the most part united near the summit and forming elliptic infra-marginal perforations, the crenate diaphanous margin purplish: stigma included within a deep terminal notch.
Near Clifton, Arizona, Dr. Anstruther Davidson, 1899.

Thysanocarpus foliosus A.Heller, 1905, Muhlenbergia 2: 47-48.
Thysanocarpus foliosus About 5 dm. high, hirsute below, pale and glaucous, branched from near the base, the branches ascending, stout: lower leaves linear-lanceolate, 6–8 cm. long, about 1 cm. wide, acutish, somewhat hirsute as well as ciliate, sparingly armed with minute retrorse points, the base hastate rather than auricled, the lobes broad and somewhat rounded; uppper ones of similar shape but gradually becoming smaller, acute or acuminate, glabrous or nearly so: flowering stems naked, about 2 dm. long; pedicles 5–7 mm. long: sepals purplish, over 1 mm. long, oblong, only the margins white: petals spatulate, slightly longer than the sepals: anthers purplish, a little exserted: silicles round-obovate, 4 mm. across, the margins entire, whitish or purplish, the greenish body somewhat rayed, densely tomentose: short style protruding from a slight notch.
The type is no. 7719, collected April 18, 1905, on the side of a ravine back of Girard station in the Tehachapi mountains, Kern county, California. The species is remarkable for its large, practically entire leaves and tomentose silicles. A relative probably of T. pulchellus F. & M., but that is described as “siliculis glaberrimis,” a fact overlooked by Greene, for in Flora Franciscana, 276, he says “pods densely tomentose.”

Thysanocarpus hirtellus Greene, 1896, Pittonia 3: 86.
Thysanocarpus hirtellus. A foot or two in height, loosely branched from the base, all parts except the inflorescence and fruit clothed rather densely with short or rather stiffly hirsute simple hairs: lowest leaves oblanceolate, coarsely toothed; cauline traingular-lanceolate, entire, with rather ample sagittate-clasping basal lobes: flowers very minute, the narrowly spatulate petals barely equalling the sepals; stamens longer and well exserted: pods round-obovoid, glabrous, venulose, the wing with 8 or 10 acutely ovate perforations, or with as many nearly closed sinuses instead (the dilated tips of the rays in this case distinct).
Discovered by the writer in a wooded cañon tributary to Dry Creek, Napa Co., California, 12 May, 1895. Very distinct from all known species by habit and pubescence; the pods also much more like those of the glabrous glaucous species T. crenatus and conchuliferus of the south than those of T. curvipes and other northern pubescent species.

Thysanocarpus laciniatus Nutt. ex Torr. & A.Gray, 1838, A Flora of North America 1: 118.
5. T. laciniatus (Nutt.! mss.): “petals as long as the calyx; silicles elliptical, glabrous, winged; the wing entire or crenate, not perforated, entire at the apex, and acuminate with the conspicuous style; leaves linear, remotely and incisely toothed.

“With the preceding.–Decumbent deep green and glabrous. Stem about a foot long. Leaves 1 1/2 inch long, and scarcely a line wide; teeth long and subulate. Silicle about 2 lines long, acute at each end; the wing diaphanous.” Nutt.

Thysanocarpus laciniatus Nutt. ex Torr. & A.Gray. var. eremicola Jepson, 1936, A Flora of California 2: 100-101.
Var. eremicola Jepson nom. n. Leaves moderately toothed or subentire, the cauline not auricled or only moderately auricled; pods suborbicular, not cuneate at base, 2 to 2 1/2 lines long, the wing membranous, without rays.–West side of the Colorado Desert and north to Inyo Co.

Locs.–Vallecito Cañon, e. slope Laguna Mts., Peirson 5942; Blair Valley, e. San Diego Co., Jepson 8692; Andreas Cañon, Palm Sprs., Mt. San Jacinto, Newlon 469a; Ord Mt., Mohave Desert, Hall & Chandler 6802; Black Mts., Death Valley, J. T. Howell 3661; Hanaupah Cañon, Panamint Range, Jepson 7040; Independence, S.W. Austin 450.
Refs.–[…]Var. eremicola Jepson. T. curvipes var. eradiatus Jepson, Man. 447 (1925), type loc. Hanaupah Cañon, Panamint Mts., Jepson 7040.

Thysanocarpus laciniatus Nutt. ex Torr. & A.Gray var. hitchcockii Munz, Bulletin of the Southern California Academy of Sciences, 31: 62.
Var. Hitchcockii Munz n. var. Capsula conferta, luteo-virida, 2.5–3 mm. lata, scabrella, cum capillis parvis clavatisque. Type, from Dante’s Point, Death Valley, P. A. Munz & C. L. Hitchcock 11016, April 6, 1928, Pomona College Herbarium No. 145825. Well distributed on the western Mohave Desert, as at Cushenberry, Hesperia, Willow Springs, Mohave, etc.

Thysanocarpus laciniatus Nutt. ex Torr. & A.Gray var. rigidus Munz, Bulletin of the Southern California Academy of Sciences, 31: 62.
Var. rigidus Munz, n. var. Plantae rigidae, compactae, 3-12 cm. altae, subpurpureae; foliis pinnatifidis; pedicellis porrectis, non recurvatis; capsulis glabris, 2.5 mm. latis, subcrenatis. Type, Laguna Camp, Laguna Mts., San Diego Co., May 16, 1925, Munz 9701, Pomona College Herbarium, No. 82645. Another collection is from 50 miles southeast of Tecate, Lower California, Munz 9572.

Thysanocarpus pulchellus Fisch. & C.A.Mey., 1835, Index Seminum, quae Hortus Botanicus Imperialis Petropolitanus pro Mutua Commutatione Offert. Accedunt Animadversiones Botanicae Nonnullae 2: 50-51.
Th. pulchellus. Th. petalis calyce longioribus; siliculis glaberrimis ala integra (non pertusa) cinctis apice subtruncatis styloque longe exserto terminatis.–Antecendenti speciei simillima, notis indicatis tamen satis distincta. Petala albida vel violascentia, parvula, calyce tamen ferme longiora.–Hab. circa coloniam ruthenorum Ross.
[Exceedingly approximate translation: “Petals longer than the calyx; siliques smooth and entire (not perforate), apex sub-truncate with the style much exserted terminally.–Similar to the previous species [Thysanocarpus curvipes] but we think it is sufficiently separate. Petals white or violet, small, calyx, however, usually longer.–Found near the Russian colony Ross.”]

Thysanocarpus radians Benth., 1849, Plantas Hartwegianas: 297.
1651 (211). Thysanocarpus radians, sp. n., foliis radicalibus runcinato-pinnatifidis, lyratisve, caulinis auriculato-sagittatis amplexicaulibus subdentatis, siliculae tomentosae ala lata orbiculata integerrima imperforata venis elevatis radiantibus notata.–Herba pedalis fere glabra a caeteris speciebus distinctissima. Folia radicalia rosulata, petiolata, angusta, 1–1 1/2–pollicaria, lobis
brevibus latis confluentibus v. inferioribus remotis, ultimus major oblongus v. lanceolatus; caulina distantia, late lanceolato-sagittata v. fere ovata, obtusiuscula, margine obscure dentata v. undulata, auriculis obtusis v. acutiusculis. Flores magnitudine T. elegantis. Ovarium stipitatum, vix marginatum, in fructu maturo ala ad basin stipitis attingit et ei cohaeret. Silicula cum ala obovato-orbicularis v. exacte orbicularis, fere 5 lin. diametro, apice saepe emarginata, loculo hinc valde convexo tomentoso, hinc fere plano ala fere glabra membranacea venis radiantibus percursa 16 ad 18 validis
superioris Sacramento.

Thysanocarpus radians Benth. var. montanus Jepson, 1901, A Flora of Western Middle California, 1st edition: 225-226.
4. T. radians Benth. Erect, commonly 1 to 1 1/2 ft. high and rarely branching; radical leaves runcinate-pinnatifid; cauline ovate-lanceolate, auriculate-clasping; fruit orbicular, 4 lines broad, glabrous or tomentose, the edge of the body divided into radiating spoke-like nerves which disappear abruptly just within the margin of the white-membranaceous wing; pedicels straight, abruptly recurved at the very summit.
Low hills or rolling plains, infrequent: Healdsburg; Sonoma; Vacaville; Antioch; and Linden (San Joaquin Co.). Apr.–May. Var. montanus is a color form; branches several from the base, ascending, 5 to 8 in. high; fruit 3 lines long, the wing bright purple.–Plateau of the Napa Mountains, north of Mt. George, Jepson, Apr. 28, 1893.

[note that this variety disappeared between the first & second editions of Jepson’s “A Flora of Western Middle California”; apparently he changed his mind]

Thysanocarpus ramosus Greene, 1887, Bulletin of the California Academy of Sciences 2: 390.
Thysanocarpus ramosus. Wholly glabrous and slightly glaucous, a foot high, the stem parted near the base into many erect, leafy and at length racemose branches; leaves 2–4 inches long, linear, those of the branches entire, or with a few scattered small but salient teeth, and an auriculate-clasping base, the lower and radical with 2–3 pairs of linear divaricate lobes: raceme naked, the pedicels slender and recurved: sepals minute, cymbiform, erect-spreading in flower, white, with a broad green mid-vein: petals twice the length of the sepals, spatulate-oblong, retuse: stamens 6, all of the same length, three on each side of the broad flat pistil: samara regularly and rather strongly concavo-convex, the crenate margin with or without some oblong perforations: style short, persistent. Species just intermediate between its very singular island congener and the mainland T. crenatus; having the foliage and branching habit of the former, nearly.

Thysanocarpus runcinatus G.Don, 1831, A General History of the Dichlamydeous Plants 1: 196.
1. T. runcinatus (Hook. l.c.) H. Native of North America, probably on the Rocky Mountains.
Runcinate-leaved Thysanocarpus. Pl. 1 foot.
Cult. An insignificant plant of easy culture; the seeds only require to be sown in the open border early in spring.
[Note- Don’s attribution of the name to Hooker in Flora Boreali-Americana is in error. Apparently what he meant is that Hooker named this species… but that Don thinks the name “Thysanocarpus runcinatus” is more appropriate.]

Thysanocarpus trichocarpus Rydb., 1903, Bulletin of the Torrey Botanical Club 30: 253-254.
Thysanocarpus trichocarpus sp. nov. Annual, perfectly glabrous, except the fruit, 1–3 dm high: stem terete, branched: lower leaves oblanceolate or oblong, sinuately dentate, thick and somewhat glaucous; uppermost leaves linear or linear-lanceolate, entire: racemes often 1 dm. long: petals slightly over 1 mm. long; blades broadly spatulate: pedicels in fruit about 5 mm. long, recurved: pod nearly orbicular, about 4 mm. wide, short-pubescent: wing-margins crenate or lobed, not fenestrate: style scarcely exceeding the wing-margin.
Utah: Silver Reef, 1894, M. E. Jones 5163b, in part (type in U.S. Nat. Herb.), 5149d and 5139d.