OF ARTS AND SCIENCES. 257 



18. E. SPH^ROCEPHALUM, Dougl. Similar, but still more diffuse : 

 leaves linear-spatulate, often revolute : the whorl of bracts on the 

 peduncle sometimes subtending a 2-4-rayed umbel, the lateral rays 

 also bracteate. — N. California and Nevada, to Washington Territory. 



++ -w Flowers glabrous: umbels simple or compound, on naked (rarely l-braeted) 

 peduncles (verticillate-bracted in n. 22): caudex diffusely branched: leaves 

 glabrate above or glabrous, oblanceolate or spatulate. 



19. E. UMBELLATCM, Torrev. Tomentose: umbel simple, of 3 to 

 10 naked rays. — Var. monocephalum, Torr. & Gray. A reduced 

 dwarf alpine form, the naked or bracteate peduncle bearing a solitary 

 involucre: leaves small. — N. California and Oregon to Colorado; 

 common. 



20. E. Torre yanum, Gray. Glabrous throughout : umbel of few 

 rays, the lateral rays bracteate in the middle and often divided : flow- 

 ers large. — In the Sierra Nevada. 



21. E. stellatdm, Benth. Tomentose: rays 2 to 4, usually and 

 often repeatedly cymosely divided : the nodes and lateral rays all 

 leafy-bracted. — £. elUpticum, Nutt. E. 2)oJyantkum, Benth., Torr. & 

 Gray. — Var. bahi^forme. Umbel very compound: leaves mostly 

 small, often densely tomentose both sides. — Oregon to S. California 

 and Arizona. 



22. E. HERACLEOiDES, Nutt. Similar, but the peduncle usually 

 verticillate-bracted : leaves narrower, mostly somewhat revolute or 

 undulate: umbel about 6- (1-11-) rayed, usually some or all of the 

 rays once or twice divided. — Washington Territory to Utah. 



++++++ Flowers glabrous : umbels usually compound, on naked peduncles : 

 caudex short and thick : leaves round to oblong, tomentose. 



23. E. COMPOSITUM, Dougl. Leaves oblong-ovate, cordate : pedun- 

 cle stout and tall : umbel compound, of 6 to 10 elongated rays. — 

 Washington Territory and Idaho to N. California. 



24. E. LoBBii, Torr. & Gray. Leaves oval or rounded : peduncles 

 short, decumbent : rays few, usually very short and undivided : flowers 

 less attenuate at base. — In the Sierra Nevada. 



* * * * Perennials, densely tomentose, with naked peduncles : bracts small : 

 involucres with 5 short erect teeth : flowers small, abruptly narrowed at 

 base, pubescent: akenes densely villous. — (Lachnogyna, Torr. & Gray.) 



25. E. ACAULE, Nutt. Very dwarf and densely matted : leaves 

 crowded, 2 or 3 lines long, oblong: peduncle half an inch Iiigh, bear- 

 ing a head of 1 to 5 nearly sessile involucres. — S. Idaho to S. W. Col- 

 orado. 



VOL. XII. (n. S. IV.) 17 



