JUN 2- 1917 Vi 
AMERICAN 
JOURNAL OF BOTANY 
Vol. IV 
May, 1917 
No. 5 
THE PERENNIAL SCAPOSE DRABAS OF NORTH 
AMERICA 
Edwin Blake Payson 
The treatment of the group of Drabas here presented grew out of 
an attempt to name some seven members of this group collected in the 
summer of 191 6 in the mountains of central Idaho by J. F. Macbride 
and the author. It soon became evident that available literature 
was entirely inadequate and that either specific lines were extremely 
hard to define or that a number of species were being treated under 
comparatively few names. Careful study of adequate herbarium ma- 
terial failed to show intermediate forms and it was noticed that each 
form (of which several specimens could usually be found) was restricted 
to a rather limited range. Differences that at first sight seemed incon- 
sequential proved to be constant. The conclusion was obvious that 
there were within this group many distinct and easily separable species. 
That they should have long passed for a few was not strange when 
their diminutive size was considered. Practically all are plants of 
arctic or alpine habitats and this alone might account for their very 
similar aspect. Under similar conditions the various species have 
developed along analogous lines. The author believes that with the 
recognition of many instead of few species practically all difficulty in 
the determination of these plants will disappear. 
In the twenty-six species comprising this group three are circum- 
polar and are also found in the main chain of the Rocky Mountains. 
One is a local species from the region of Hudson Bay. Twenty- two 
are peculiar to western North America and their distribution will 
be considered in detail. Seven have been found in the Rocky Moun- 
tains proper and, of these seven, two have possibly been developed 
farther westward and have migrated east. Fifteen are truly western, 
253 
