STUDIES IN THE CRUCIFER. 187 
STUDIES IN THE CRUCIFERÆ.— III. 
1. Certain species of ARABIS. 
I have made repeated careful and laborious efforts to 
ascertain to what extent genuine Arabis Holbellii, a Green- 
land plant as to the original, is indigenous to British America 
and the United States. And while the results attained can 
not be considered final, I think it well to put them upon 
record. 
And for one thing, I am convinced that A. Holbællii does 
not occur, so far as known, upon United States territory; 
nor have I yet met with satisfactory evidence of its occur- 
rence on this continent; though it is to be expected from 
very far northward, along the shores of the Arctic seas. 
Our Rocky Mountain and other far western and northwest- 
ern plants that have been so referred must, it seems to me, 
be treated as fair subspecies at the least. A number of 
such segregates have already been proposed, and I shall 
here present the characters of several more. 
But first of all, I shall attempt, what seems never yet to 
have been given, a real diagnosis of the original of this 
group, which has hitherto been recognizable only by means 
of the plate in the Flora Danica. 
A. Horscrun, Hornem. Stem stoutish, simple, 6 inches 
high or more, very leafy below; leaves about $ inch long 
including the short distinct petiole, the blade lanceolate, 
acutish, entire, the whole canescent with a minute stellate 
pubescence; cauline leaves few, oblong, sessile and auricu- 
late- or subsagittate-clasping, either wholly glabrous, or the 
