PEA FAMILY 139 



2. MEDICAGO. 



Herbs with pinnately compound leaves (leaflets only 3) 

 and small usually yellow flowers in short racemes. Intro- 

 duced plants of some forage value, now running wild. The 

 ordinary Alfalfa, with blue flowers, is a member of this genus. 



1. M. hispida Gaertn. Bur Clover. Herbage nearly gla- 

 brous. Leaflets obovate, about y 2 in. long, rigidly toothed. 

 Peduncles 3 to 5-flowered. Pod twisted into 3 to 5 coils, the 

 thin edge with hooked or curved prickles. (M. denticulata 

 Willd.) — Sparingly introduced; the stems, which are a few 

 inches to 2 ft. long, lie flat on the ground and bear numerous 

 burs. 



2. M. lupulina L. Nonesuch. Black Medick. Much like 

 Bur Clover but with more flowers and kidney-shaped 1-seeded 

 pods which are not at all bur-like. — Grows at Crockers and 

 perhaps elsewhere near settlements. 



M. apiculata Willd., if found, may be distinguished by its 

 several-seeded, spirally coiled, unarmed pods. Otherwise it 

 is exactly like M. hispida. 



3. TRIFOLIUM. Clover. 

 Herbs with palmately compound leaves (leaflets 3 in our 

 species) and white, red or purple flowers in head-like clus- 

 ters. Pod oblong, 1 to 8-seeded. 



A. Flower-heads subtended by an involucre of distinct or 

 united bracts. 



Bracts minute (rarely -fV in. long) 1. T. monanthutn. 



Bracts conspicuous, at least half as long as calyx. 

 Herbage plainly pubescent. 



Involucre flat; flowers over l / 2 in. long 2. T. obtusifiorum. 



Involucre cup-shaped; flowers much smaller 6. T. microcephalum. 



Herbage glabrous. 



Heads over J4 in. broad; leaflets mostly 24 in- 

 long. 

 Leaflets linear or linear-lanceolate, not veiny. . . 3. T. trident atum. 



Leaflets broader, veiny 4. T. spinulosum. 



Heads less than J4 in. broad; leaflets mostly l A 



in. long 5. T. variegatum. 



B. Flower-heads naked. 



Plant conspicuously pubescent. 



Leaflets acute 7. T. longipes. 



Leaflets obtuse. 



Heads dense, conic, rose-red 8. T. pratense. 



Heads dense, gray; calyx-teeth long-hairy 13. T. macraei. 



Heads loose, pale 9. T. breweri. 



