Flora of North America species comparison

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Athysanus

athysanus, sandweed
Habit Annuals; not scapose; glabrous or pubescent, trichomes simple mixed with short-stalked, forked, 3-rayed, or cruciform ones.
Stems

(few from base), ascending, branched.
Leaves

basal and cauline;

petiolate or sessile;

basal not rosulate, shortly petiolate, blade margins entire or dentate;

cauline shortly petiolate or sessile, blade (base not auriculate), margins entire or dentate.
Racemes

(corymbose, several-flowered, secund, lax), considerably elongated in fruit.
Flowers

(cleistogamous and/or chasmogamous);

sepals suberect, oblong, lateral pair not saccate basally, (glabrous or pubescent);

petals white, (usually rudimentary, or well-developed and exceeding sepals, rarely absent), spatulate or oblong, claw indistinct;

stamens subequal;

filaments slightly dilated or not basally;

anthers ovate to globose;

nectar glands lateral, each side of lateral stamens.
Fruiting pedicels

recurved or reflexed, slender or stout, (glabrous or pubescent).
Fruits

(pendulous), silicles, indehiscent or very tardily dehiscent, sessile, usually orbicular or obovate to elliptic, rarely oblong, twisted or flattened, latiseptate;

valves each not veined or veins prominent, pubescent or glabrous;

replum rounded;

septum absent or complete;

ovules 2–12 per ovary;

style obsolete or distinct;

stigma capitate.
Seeds

uniseriate, flattened, not winged, oblong;

seed coat not mucilaginous when wetted;

cotyledons accumbent.

Athysanus
Distribution
from USDA
w North America; nw Mexico
[BONAP county map]
Discussion

Species 2 (2 in the flora).

Athysanus and Heterodraba are strikingly similar in almost all aspects except for the differences in the key below. Although R. C. Rollins (1993) mentioned nothing about their relationship, he keyed them out in one couplet. Their species are more closely related to each other than to other Brassicaceae. In my opinion, the recognition of two independent monotypic genera obscures their sister phylogenetic relationship. Both genera were described simultaneously by Greene, and since W. L. Jepson (1901) transferred the type of Heterodraba to Athysanus, the latter name has nomenclatural priority.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
1. Fruits 1-locular, not twisted; valves usually pubescent, rarely glabrous, some or all trichomes hooked; seeds 1.
A. pusillus
1. Fruits 2-locular, flat or slightly twisted; valves glabrous or pubescent, trichomes not hooked; seeds often 2+.
A. unilateralis
Source FNA vol. 7, p. 267. Author: Ihsan A. Al-Shehbaz.
Parent taxa Brassicaceae > tribe Arabideae
Subordinate taxa
A. pusillus, A. unilateralis
Synonyms Heterodraba
Name authority Greene: Bull. Calif. Acad. Sci. 1: 72. (1885)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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