50 LEGUMINOS.E. (PULSE FAMILY.) 



3. R. aromatica, Ait., var. trilobata, Gray. A shrub 2 to 5 feet high, 

 diffusely branched, strongly scented : leaflets cuneate-obovate or rhomboidal, 

 coarsely toothed above and often 3-lobed : flowers in clustered scaly bracted 

 spikes like catkins, preceding the leaves, yellowish : fruit flattish, somewhat 

 viscid. R. trilobata, Nutt. Common throughout the Rocky Mountains to 

 the Upper Missouri, and westward. 



ORDER 25. L,EGIJMINOS^E. (PULSE FAMILY.) 



Plants with irregular or sometimes regular flowers, mostly 10 mon- 

 adelphous or diadelphous stamens, and a single simple free pistil 

 becoming a legume in fruit. Leaves alternate, with stipules, usually 

 compound. 



SUBORDER I. PAPILIONACE^E. 



Flower irregular. Calyx mostly 5-cleft or 5-toothed. Corolla of 5 

 petals (rarely fewer) ; one (standard) superior, larger and always 

 external, covering in the bud the two lateral ones (wings), and these 

 covering the inferior pair, which together form the keel, this in turn 

 enclosing the stamens and pistil. Style generally inflexed or incurved. 



* Stamens distinct 

 *- Leaves digitately 3-foliolate. 

 1. Thermopsis. Stipules conspicuous, and yellow flowers in racemes. 



- *- Leaves unequally pinnate. 

 2 Sopliora. Pod thick, large, several-seeded, often, transversely constricted. Leaves 



coriaceous. 



9. Amorpha. Pod small, 1 to 2-seeded. Petal one. Stamens inonadelphous at the very 

 base. 



* * Stamens monadelphous or diadelphous (9 and IX 



t- Anthers of two forms : filaments strictly monadelphous : leaves digitate, of more than 3 



entire leaflets. 



3. laipinns* Calyx 2-lipped. Standard with recurved sides : keel falcate. Pod large, 



straight 



- - Anthers reniform. 



H. Leaflets 3 (rarely 5 to 7), denticulate or serrulate : stamens diadelphous or nearly so : 

 pods small and enclosed in the calyx. 1 



4. Trifolium. Flowers capitate. Corolla persistent, united with the filaments. 



H- ** Leaves unequally pinnate (very rarely digitate or simple) ; leaflets entire: no tendril. 

 = Flowers in axillary umbels or solitary : stamens diadelphous. 



5. Hosackia. Corolla yellow or partly white or turning reddish : claw of the standard 



usually remote from the others. Pod linear, several-seeded. 



= = Flowers in spikes, racemes, or heads, never umbellate, 

 a. Herbage glandular-dotted : stamens mostly monadelphous : pod usually indehiscent 



6. Psoralea. Herbs, with 3 to 7-foliolate leaves and axillary spikes or racemes. Pod one- 



ovuled, one-seeded. 



1 Medicago is an introduced genus, with small flowers in axillary racemes or spikes, petals 

 free and deciduous, arid the pod spirally coiled or curved. See foot-note, p. 54. 



