THE PERENNIAL SCAPOSE DRABAS OF NORTH AMERICA 255 
Much of the material seen has been examined by Dr. E. Gilg. He 
used a number of herbarium names which have unfortunately never 
been published and there is some confusion as to his conception of 
types. His determinations were very valuable and often served to 
corroborate the author's opinions. The types of the species published 
by Macbride and Payson are to be found in the Gray Herbarium at 
Harvard; those published by the author alone are in the Rocky Moun- 
tain Herbarium, with the exception of D. Mulfordae, which is at St. 
Louis. Some names are omitted from this treatment that might be 
expected here. D. crassifolia Graham is scapose but belongs rather 
to the biennial class than to these densely cespitose plants. The 
identity of D. densifolia Nutt. remains obscure. Material labeled 
as typical in the Gray Herbarium seems referable to D. oligosperma. 
Draba euryc'arpa Gray has long been considered related to this group 
of plants, but there seems to be some doubt about it being a Draba. 
Key to the American Perennial Scapose Drabas 
Leaves bearing no stellate or conspicuously branching hairs. 
Leaves densely imbricated, forming compact, subspherical 
tufts on the ends of the caudex branches, pods 
corymbose. 
Pods glabrous 4.. D. globosa. 
Pods pubescent, more densely cespitose 5. D. sphaerula. 
Leaves not so densely imbricated, scapes mostly over i cm. 
long. 
Style very short, stigma sessile or subsessile. 
Pods racemose, flowers yellow i. D. alpina. . 
Pods corymbose, flowers white 2. D. fladnizensis. 
Style evident, .5 mm. or more long. 
Pods glabrous. 
Leaves 5-6 mm. long, obovate '. . . 15. D. cylomorpha. 
Leaves 2-3 mm. long, pods narrowly elliptical 3. D. oreibata. 
Pods pubescent. 
Leaves broadly oblanceolate 16. D. Lemmoni. 
Leaves linear, midvein prominent. 
Leaves glabrous except for strong cilia on the 
margins j. D. Nelsonii. 
Leaves pubescent, cilia weak 6. D. Douglasii. 
Leaves bearing some stellate or branching hairs. 
Pods glabrous. 
Style less than .5 mm. long. 
Pods linear (i cm. or more long) 13. D. lonchocarpa. 
Pods broader, less than i cm. long. 
Leaves stellate 12. D. nivalis. 
