42 LEGUMINOSJS. (PEA FAMILY.-) 



4. TRIFOLIUM, L. CLOVER. 



Calyx 5 cleft with nearly equal teeth, persistent. Corolla withering, persistent; wings 

 narrow, keel short ohtuse. Stamens usually diadelphous. Style filiform. Pod small 

 and usually inclosed in the calyx, membranaceous, indehiscent or dehiscent at the ventral 

 suture, 1 to 6-seeded. Herbs with leaves palmately 3 or rarely 5-7-foliolate; stipules 

 adnate to the petiole; flowers in capitate racemes, spikes or umbels, rarely few or solitary; 

 peduncles axillary or only apparently terminal. 



All our species annual. 



1. Heads not involucrate; ovules 3. 



* Heads apparently terminal; flowers sessile, not reflexed; calyx teeth plumose, filiform. 



1. T. Macrsei, Hook. & Arn. Somewhat villous, erect, 6 to 12 inches high; sti- 

 pules ovate to lanceolate; leaflets obovate to narrowly oblong, obtuse or retuse, serrulate, 

 about half an inch long; flowers dark purple, 3 lines long, in dense ovate long peduncled 

 heads; calyx very villous; the straight teeth as long as the petals, often tinged Adth 

 purple; pod 1 -seeded. 



Var. dichotomum, Brew. A taller and stouter form, with larger flowers in heads 

 nearly an inch long; corolla more conspicuous, tipped with white. 



* * Heads axillary, small; flowers on short pedicels, at length reflexed; calyx teeth subu- 



late; mostly smooth. 



2. T. ciliatum, Nutt. Erect, often 1 to 2 ft. high; leaflets similar to the last; 

 corolla white or purplish, little exserted, $ lines long; calyx tube campanulate; the 

 lanceolate teeth very acute, rigid, the scarious margin rigidly ciliate. 



3. T. gracilentum, Torr. & Gr. Erect, slender, a foot high or less; stipules lanceo- 

 late; leaflets cuneate oblong to ovate or obcordate, retuse, about half an inch long, 

 serrulate; flowers pale rose-color or purplish on pedicels a line long or less; calyx cam- 

 panulate, the subulate teeth nearly equaling the corolla. 



4. bifidum, Gr. Exactly like the last, but the leaflets narrow, the sides sparingly 

 toothed or entire, and all deeply notched or cleft at the apex. 



2. Heads subtended by an involucre; peduncles axillary; flowers sessile, not reflexed. 



* Involucre not membranaceous, deeply lobed, and the lobes laciniately and sharply toothed; 



corolla not becoming inflated. 



5. T. involucratum, Willd. Smooth; stems ascending, often a span high or more; 

 leaflets mostly oblanceolate and acute at each end, a half to an inch long; flowers half an 

 inch long, in close heads, purple or rose-colored; the narrow calyx teeth all entire; ovules 

 mostly 5 or 6. 



Var. heterodon, Wat. Heads larger and leaflets broader; some of the calyx teeth 

 setaciously cleft. 



6. tridentatum, Lindl. Smooth or glandular-puberulent, slender and usually erect, 



