1915] SHULL—XANTHIUM 481 
canum Walt. which was for a time called X. strumarium in the 
east, and which was redescribed by BRITTON in 1901 as X. glabra- 
tum. In the second edition of Brirron and Brown this species 
is now listed as X. americanum Walt. It seems clear from the 
descriptions that type III, with rather slender, oblong, essentially 
glabrous burs, should bear the name X. canadense Miller (Gard. 
Fic. 7.—X. globosum Shull, at the same age as X. pennsyloanicum Wallr. in fig. 6 
Dict. ed. 8. no. 2. 1768); with this species, X. americanum Walt. 
(x. Car. 231. 1788) and X. glabratum Britt. (Britt. Manual 912. 
1901) are synonymous. : 
Type II, with oblong pubescent fruit, agrees fairly well with the 
description of X. pennsylvanicum Wallr., and must on the basis 
