160 



and is nearer to it in general habit, but differs in the thicker 

 leaves (usually deeply dentate),- dense and very short pubes- 

 cence, thicker and more torulose pod. These characters, 

 together with the larger flowers, very short style, which is 

 scarcely more than 0.5 mm. long, and the stems, decumbent at the 

 base, distinguish it -from the preceding species. The following 

 specimens are at hand : Sandy Plains, Lower Bow Park, vicinity 

 of Banff, Alberta, \?,go, McCalla 2272; Banff, 1887,/. Fowler; 

 about Mackenzie River, from lat. 60° to 68°, Richardson. 

 Emerald Lake, Alberta, 1904, J. Macoiin 6^^jj and C. H. 

 Shaw log. 



Pilosella virgata (Nutt.) Rydb. 

 Sisyinbiium virgatiun Nutt.; T. & G. Fl. i : 93. 1838. 

 Stenophragma znrgatiim Greene, Y\t\.or\'\R '^: 138. 1896. 

 Arabis Brebneriana A. Nelson, Bull. Torrey Club 25 : 373. 1898. 



The first one to transfer this species to a genus with Arabis 

 Thaliana L. as the type was Dr. Greene. He was not, however, 

 the first one who saw the relationship between these two species, 

 for in Torrey & Gray's Flora they are associated with S. Juiviilc, 

 S. glauaun Nutt. and 5". paucifloruiii Nutt. in a section Arabi- 

 dopsis. Except the last one, which is doubtful and unknown to 

 the writer, the group comprises just those species which the writer 

 here regards as constituting in North America the genus Pilo- 

 sella. The more he studies the work of Thomas Nuttall, who 

 contributed most to the knowledge of these species as well as 

 numerous others to Torrey & Gray's Flora, the more he ad- 

 mires that old botanist's acuteness. In ability to recognize 

 relationships, he surpassed even Dr. Torrey and Dr. Gray. 



The most extended description of this species was made by 

 Professor Aven Nelson under the name of Arabis Brebneriana. 

 The only discrepancy we find is that the valves of the pod 

 are said to be " obscurely few-nerved," for besides the few obscure 

 nerves there is in each a prominent midrib, making the pod angu- 

 lar just as in Pilosella Thaliana. The only difference in the 

 structure of the pod is that the septum of the pod has a faint 

 midrib, which is obsolete in P. Thaliana, P. Novae- Angliae, and 



