130 LEGUMINOS^E. (PULSE FAMILY.) 



9. PETALOSTEMON, 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, al- 

 luding to the peculiar union of these organs in this genus.) 



1. P. Violaceus, 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, Michigan to Minnesota 

 and southward. July. 



2. P. candidus, Michx. Smooth ; leaflets 7-9, lanceolate or linear-ob- 

 long ; heads oblong, when old cylindrical ; bracts awned, longer than the nearly 

 glabrous calyx ; corolla white. With No. 1. July. 



3. P. villdsus, Nutt. Soft-downy or silky all over; leaflets 13-17, linear 

 or oblong, small (4" - 5" long) ; spikes cylindrical ( 1' - 5' long), short-peduncled, 

 soft-villous ; corolla rose-color. N. Wisconsin (LakePepin, &c. T.J.Hale) and 

 westward. 



10. AMOBPHA, L. FALSE INDIGO. 



Calyx inversely conical, 5-toothed, persistent. Standard (the other petals en- 

 tirely wanting !) wrapped around the stamens and style. Stamens 10, monadel- 

 phous at the very base, otherwise distinct. Pod oblong, longer than the calyx, 

 1 - 2-seeded, roughened, tardily dehiscent. Shrubs, with odd-pinnate leaves ; 

 the leaflets marked with minute dots, usually stipellate. Flowers violet O pur- 

 ple ; crowded in clustered terminal spikes. (Name, apopcfrn, wanting form, from 

 the absence of four of the petals.) 



1. A. fruticbsa, L. (FALSE INDIGO.) Rather pubescent or smoothish; 

 leaflets 8 -12 pairs, oval, scattered; pods 2-seeded. River-banks S. Penn. to 

 Wisconsin and southward. June. A tall shrub : very variable. 



2. A. can6scens, Nutt. (LEAD-PLANT.) Low (l-3 high), whitened 

 with hoary down ; leaflets 15-25 pairs, elliptical, crowded, small, smoothish above 

 with age ; pods 1 -seeded. Prairies and crevices of rocks, Michigan to Wiscon- 

 sin and southwestward. July. Supposed to indicate lead-ore. 



11. ROBtNIA, L. LOCUST-TREE. 



Calyx short, 5-toothed, slightly 2-lipped. Standard large and rounded, 

 turned back, scarcely longer than the wings and keel. Stamens diadelphous. 

 Pod linear, flat, several-seeded, margined on the seed-bearing edge, at length 2- 

 valved. Trees or shrubs, often with prickly spines for stipules. Leaves odd- 

 pinnate, the ovate or oblong leaflets stipellate. Flowers showy, in hanging 

 axillary racemes. Base of the leaf-stalks covering the buds of the next year. 

 (Named in honor of John Robin, herbalist to Henry IV. of France, and his son 

 Vespasian Robin, who first cultivated the Locust-tree in Europe. ) 



