21. ASTRÁGALUS, Tourn. Milk-Vetch.
Calyx 5-toothed. Corolla usually long and narrow; standard narrow, equalling or exceeding the wings and blunt keel, its sides reflexed or spreading. Stamens diadelphous. Pod several–many-seeded, various, mostly turgid, one or both sutures usually projecting into the cell, either slightly or so as to divide the cavity lengthwise into two.—Chiefly herbs (ours perennials), with odd-pinnate leaves and spiked or racemed flowers. Mature pods are usually necessary for certain identification of the species. (The ancient Greek name of a leguminous plant, as also of the ankle-bone; but the connection between the two is past all guess.)
I. Pod turgid, completely or imperfectly 2-celled by the intrusion of the dorsal suture, the ventral suture being not at all or less deeply inflexed.—Astragalus proper.
[*] Pod plum-shaped, succulent, becoming thick and fleshy, indehiscent, not stipitute, completely 2-celled.
1. A. caryocárpus, Ker. (Ground Plum.) Pale and minutely appressed-pubescent; leaflets narrowly oblong; flowers in a short spike-like raceme; corolla violet-purple; fruit glabrous, ovate-globular, more or less pointed, about {2/3}´ in diameter, very thick-walled, cellular or corky when dry.—Sask. and Minn. to Mo., Col., and Tex. May.
2. A. Mexicànus, A. DC. Smoother, or pubescent with looser hairs, larger; leaflets roundish, obovate, or oblong; flowers larger (10–12´´ long); calyx softly hairy; corolla cream-color, bluish only at the tip; fruit globular, very obtuse and pointless, 1´ or more in diameter; otherwise like the last.—Prairies and open plains, Ill. to Kan., south to Tex. The unripe fruits of both resemble green plums—whence the popular name—and are eaten, raw or cooked, by travellers.
3. A. Platténsis, Nutt. Loosely villous; stipules conspicuous; leaflets oblong, often glabrous above; flowers crowded in a short spike or oblong head, cream-color often tinged or tipped with purple; fruit ovate, pointed, and with the calyx villous.—Gravelly or sandy banks, Minn. to Ind. and Ala., west to Col. and Tex.—Var. Tennesseénsis, Gray, has the pod oblong and slightly curved, and much less fleshy. May.
[*][*] Pod dry, coriaceous, cartilaginous or membranous, dehiscent.
[+] Pod completely 2-celled, sessile.
4. A. mollíssimus, Torr. Stout, decumbent, densely silky-villous throughout and tomentose; leaflets 19–29, ovate-oblong; peduncles elongated; spikes dense, with rather large violet flowers (6–12´´ long); pod narrow-oblong (5–9´´ long), glabrous, somewhat obcompressed and sulcate at both sutures, at length incurved.—Neb. to Kan. and Tex., west to Col. The most common "loco"-plant, and said to be very poisonous to cattle.