220 LEGUMINOSAE. 



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 places, especially near the seashore. 



Trifolium tridentatum Lindl. Annual, glabrous; stems erect, very slender, 

 10-40 cm. high; leaflets lance-linear, acute, spinulose-serrulate, 2-5 cm. long; 

 stipules lanceolate, acuminate, the upper ones laciniate; heads globose, the 

 largest 2 cm. broad; involucre laciniately cleft, shorter than the head; calyx- 

 lobes subulate with a tooth on each side near the base; corolla purple and 

 white. 



In dry open ground, British Columbia to California. First collected by 

 Douglas on the Columbia River. 



Trifolium oliganthum Steud. Annual, glabrous; stems very slender, erect 

 or ascending, usually branched from the base; stipules laciniately cleft; leaf- 

 lets serrulate, the lower obovate or oblanceolate, obtuse or retuse, the upper 

 linear or linear-lanceolate, acute or acuminate; stipules laciniately cleft; 

 heads very small, 5— 7-flowered; involucre small, deeply cleft; calyx-teeth 

 subulate, rigid, entire; corolla purple and white. 



In moist places, common. First collected by Nuttall at the mouth of the 

 Willamette River. 



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, 4-12-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 repens L. White Clover. Perennial, glabrous or sparsely 

 pubescent, with creeping stems 10-30 cm. long, which root at the nodes; 

 leaflets obovate, obtuse or notched at apex, cuneate at base, denticulate, 1-2 

 cm. long; petioles elongated; stipules. narrow, acute; peduncles longer than the 

 leaves; head globose; flowers white, 6-10 mm. long, pedicelled, at length 

 reflexed; calyx-teeth acuminate, shorter than the tube. 



Introduced from Europe, common. 



Trifolium hybridum L. Alsike Clover. Perennial, erect or decumbent, 

 not creeping, glabrous or nearly so, the stem 30-60 cm. long; leaflets obovate, 

 obtuse or notched, cuneate at base, sharply serrulate, 1-2.5 cm. long; petioles 

 about as long as the leaflets; stipules membranous, ovate-lanceolate, acu- 

 minate; peduncles elongated; heads globose; flowers pink or pinkish, 6-8 mm. 

 long, on slender pedicels, at length reflexed; calyx-teeth subulate, about as 

 long as the tube, much shorter than the corolla. 



Introduced from Europe, common. 



Trifolium eriocephalum Nutt. Perennial, villous-pubescent; root stout, 

 fusiform; stems erect, 15-20 cm. high; leaflets oblong to oblong-lanceolate, 

 serrulate, 2-5 cm. long; stipules lanceolate, acuminate; heads dense, ovoid to 

 subglobose; flowers whitish, at length reflexed; calyx-teeth very plumose. 



In gravelly soil, in prairies. 



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

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



