FLOWERIXG PLANTS AND FLRXS OF ARIZONA 443 



9. Plant acaulescent or nearly so, cespitose (10). 



10. Leaflets never more than 3, narrowly lanceolate, entire, acerose; 

 involucre often much reduced but some of the bracts 2 mm. long or 

 longer, subulate to ovate-lanceolate, scarious-margined; calyx 

 rather sparsely villous 9. T. dasyphtllum. 



10. Leaflets often more than 3, elliptic to obovate, doubly dentate, mucronate ; 

 involucre minute, almost obsolete, all of the bracts less than 2 mm. 

 long, truncate or erose, entirely scarious; calyx densely villous. 



10. T. SUBCAULESCEX-. 



8. Involucre none (11). 



11. Plants annual or biennial; flowers not becoming reflexed (12). 



12. Calyx villous with long hairs; rachis of the head not conspicuously 

 prolonged; flowers not becoming noticeably reflexed; corolla dark 

 purple and whitish 11. T. albopurfureum. 



12. Calyx glabrous or nearly so; rachis of the head conspicuously prolonged 



and exserted, especially after anthesis; outer flowers strongly re- 

 flexed after anthesis; corolla pink to reddish purple. 



12. T. GRACILEXTUM. 



11. Plants perennial, but sometimes short-lived (13). 



13. Leaves (the uppermost pair) subtending the sessile or subsessile head: 



stipules very large and conspicuously veined; leaflets ovate or 

 elliptic, the larger ones 2 cm. long or longer; heads at anthesis 

 seldom less than 20 mm. in diameter; flowers not becoming reflexed; 

 corolla rose-colored. 13. T. pratexse. 



13. Leaves not subtending the head; flowers (the lower ones) becoming re- 

 flexed after anthesis (14). 

 14. Calyx teeth glabrous or nearly so, less than twice as long as the tube; 

 leaf blades thin: peduncle glabrous or nearly so (15). 

 15. Stems repent and often rooting at the nodes; corolla white or 



tinged with pink 14. T. repexs. 



15. Stems erect or ascending (16). 



16. Calyx teeth setaceous, more or less flexuous; banner petal broad 



and refuse at apex 15. T. macilenttjm. 



16. Calyx teeth subulate, straight or nearly so; banner petal rela- 

 tively narrow, acutish at apex 16. T. hybridum. 



14. Calyx teeth" villous-plumose, 2 to 3 times as long as the tube; leaf 



blades thickish; peduncle sparsely to densely villous, especially 



toward the apex (17) . 



17. Heads about 15 mm. long from the summit of the peduncle; 



larger leaflets seldom more than 2 cm. long, elliptic to narrowly 



obovate, sparselv sericeous beneath with short hairs. 



17. T. RUSBYI. 



17. Heads seldom less than 20 mm. long from the summit of the 

 peduncle; larger leaflets 3 cm. long or longer, densely sericeous 

 beneath with long hairs, at least when young (18). 

 18. Leaflets narrowly lanceolate, 5 to 10 times as long as wide, 

 sharply acuminate at apex, the marginal teeth incurved. 



18. T. NETJROPHYLLUM. 



18. Leaflets oblong-lanceolate or slightly oblanceolate, 3.5 to 4 

 times as long as wide, obtusish and apiculate at apex, the 

 marginal teeth spreading 19. T. villiferum. 



1. Trifolium microcephalum Pursh, Fl. Amer. Sept. 478. 1814. 

 Pinal Mountains, Gila County (McLellan and Stitt in 1935). near 



Superior, Pinal County {Harrison and Peebles 1707). Montana to 

 British Columbia, south to Arizona and Baja California. 



2. Trifolium variegatum Nutt. ex Torr. and Gray, Fl. North Amer. 1: 



317. 1838. 

 Near Kirkland, Yavapai County (Harrison and Peebles 4194), 

 Santa Rita Mountains, Pima County (Thomber in 1905). Montana 

 to British Columbia, south to Arizona and Baja California. 



