Calyx 5-cleft or toothed. Corolla imperfectly papilionaceous; petals all on claws; the standard heart-shaped, inserted in the bottom of the calyx; the keel and wings borne on the middle of the monadelphous sheath of filaments, which is cleft down one side. Stamens 10, rarely 9. Pod membranaceous, 1-seeded, indehiscent, enclosed in the persistent calyx.—Mostly herbs, more or less glandular-dotted, with minute stipules; the small flowers in terminal spikes or heads. (Named for Samuel Dale, an English botanist.)
[*] Glabrous; flowers white or rose-color; leaflets 4–20 pairs; annuals.
1. D. alopecuroìdes, Willd. Erect (1–2° high); leaflets 10–20 pairs, linear-oblong; flowers light rose-color or whitish, in cylindrical spikes; bracts ovate-lanceolate, acuminate, deciduous; calyx very villous, with long slender teeth.—Alluvial soil, Minn. to Ill. and Ala., west to the Rocky Mts.
2. D. laxiflòra, Pursh. Erect (1–4° high), branching; leaflets 3–5 pairs, linear, 2–3´´ long; spikes loosely-flowered; bracts conspicuous, persistent, almost orbicular and very obtuse; petals white; calyx densely villous, the long teeth beautifully plumose.—Iowa and Mo. to Tex., west to Col.
[*][*] Pubescent; leaflets 3–4 pairs; perennial herbs.
3. D. aùrea, Nutt. Stems erect and simple, 1–3° high; leaflets oblong-obovate to linear-oblong, more or less silky-pubescent; spikes solitary, oblong-ovate, very compact and densely silky; bracts short, rhombic-ovate; petals yellow.—On the plains, Mo. to Tex., and westward.
4. D. lanàta, Spreng. Very pubescent throughout, 1–2° high, branching; leaflets obovate to oblong-obovate, 2–3´´ long; spikes slender, rather loose, the obovate acute bracts equalling the small short-toothed calyx; petals short, purple.—Central Kan. to Tex., and westward.
16. PETALOSTÈMON, Michx. Prairie Clover.
Calyx 5-toothed. Corolla indistinctly papilionaceous; petals all on thread-shaped claws, 4 of them nearly similar and spreading, borne on the top of the monadelphous and cleft sheath of filaments, alternate with the 5 anthers; the fifth (standard) inserted in the bottom of the calyx, heart-shaped or oblong. Pod membranaceous, enclosed in the calyx, indehiscent, 1–2 seeded.—Chiefly perennial herbs, upright, glandular-dotted, with crowded odd-pinnate leaves, minute stipules, and small flowers in very dense terminal and peduncled heads or spikes. (Name combined of the two Greek words for petal and stamen, alluding to the peculiar union of these organs in this genus.)
1. P. violàceus, Michx. Smoothish; leaflets 5, narrowly linear; heads globose-ovate, or oblong-cylindrical when old; bracts pointed, not longer than the silky-hoary calyx; corolla rose-purple.—Dry prairies, Minn. to Ind. and Tex., west to the Rocky Mts. July.