148 LEGUMINOSAE. 



ends, acute or obtuse, cuspidate, 2-4 cm. long, strongly veined, the veinlets 

 usually protruding as slender teeth; stipules nearly as long as the leaflets, 

 acute, entire, or nearly so; peduncles 5-10 cm. long; heads globose or oblong- 

 cylindric, 2-3 cm. long; flowers red, sessile, at length reflexed, 12-15 mm. long; 

 calyx-tube strongly nerved, the subulate teeth twice as long, the lowest 

 straight, the others twisted. Low meadows, common. 



Trifolium pratense L. Red Clover. Perennial, erect or decumbent, rarely 

 branched, 20-40 cm. high, somewhat pubescent throughout; leaflets elliptic 

 or obovate, obtuse or rarely emarginate, denticulate, 1-4 cm. long, frequently 

 dark-spotted near the middle; petioles short; heads globose or ovoid, sessile 

 or nearly so, 2 cm. long; flowers red, 10-12 mm. long; calyx-teeth subulate, 

 shorter than the corolla. Introduced and common. 



Trifolium latifolium (Hook.) Greene. Sparsely puberulent, especially 

 above; perennial from a stout root but with long slender root-like under- 

 ground branches; stems slender, 10-15 cm. high; stipules broadly ovate, 

 acuminate, obscurely toothed or lobed; petioles slender; leaflets mostly ovate, 

 denticulate, obtuse, mucronate, 5-20 mm. long; peduncles exceeding the 

 leaves; heads globose, 1.5-2 cm. broad, loosely 15-30-flowered; pedicels as 

 long as the calyx-tube; calyx teeth subulate, longer than the tube; flowers 

 whitish, 10-12 mm. long, all reflexed in age. In open woods, simulating 

 closely in appearance common white clover. 



Trifolium spinulosum Dougl. (T. fimbriatum Lindl. ?.) Perennial by 

 creeping rootstocks, glabrous throughout; branches prostrate or ascending, 

 20-40 cm. long; leaflets oblong-obovate to oblanceolate, spinulose-denticulate, 

 the lower obtuse or even retuse, the upper acute or acuminate, mostly 1-3 

 cm. long; stipules triangular, acuminate, with a few teeth; heads subglobose, 

 1-2 cm. broad; involucre short, laciniately parted; calyx lobes unequal, 

 subulate, somewhat spiny, 2-3 times as long as the tube; petals purple with 

 paler or white tips. In wet meadows. 



Trifolium variegatum Nutt. Annual, glabrous throughout; stems decum- 

 bent, 10-30 cm. long, branching, leafy; leaflets obovate to obcordate, minutely 

 and sharply serrulate, veiny, 6-12 mm. long; stipules broad, f ringed-toothed; 

 peduncles very slender, longer than the leaves; heads small, 4-1 2-flowered ; 

 involucre shorter than the flowers, campanulate, fringe-toothed ; calyx glabrous, 

 its teeth subequal, subulate, longer than the tube; petals purple with white 

 tips, pods 2-seeded. In moist ground, common. 



Trifolium cyathiferum Lindl. Annual, glabrous; stems weak, ascending, 

 10-30 cm. high; leaflets oblanceolate or obovate, serrulate, acute, obtuse or 

 truncate, cuneate at base, 1-2 cm. long; petioles slender; stipules ovate or 

 lanceolate, laciniate; peduncles longer than the leaves; heads commonly 1.5 

 cm. broad; involucre large and conspicuous, whitish with green margin, 

 many- nerved, with short sharply-toothed lobes; flowers whitish; calyx mem- 

 branous, prominently 5-nerved, the nerves prolonged and branched, equalling 

 the corolla; pod 2-seeded. Springy gravelly places, rare. 



Trifolium microcephalum Pursh. Annual, erect or spreading, soft villous; 

 stems 5-30 cm. long; leaflets obovate, usually retuse, serrulate, 8-12 mm. 

 long; petioles slender; stipules entire, acuminate; heads small, many-flowered; 

 involucre membranaceous, about 9-lobed, the lobes 3-nerved, entire; calyx 

 hairy, the teeth subulate; corollas pale pink; pods glabrous, 1-seeded. In 

 gravelly or sandy soil. 



209. MEDICAGO. 



Annual or perennial herbs with small trifoliolate leaves; leaf- 

 lets toothed; flowers small, yellow or violet, in axillary spikes; 

 pods 1-several-seeded, curved or coiled. 



