AN INTERESTING MODIFICATION IN XANTHIUM 4I 
bur shown in Figure 3, only twelve contained seeds. And a small box 
of burs coming from direct descendants but two generations removed 
from the original plant showed complete sterility, entire absence of 
seeds. 
Fig. I. X anthium canadense var. globuliforme Crevecoeur. Burs about 
natural size. 
The history of this interesting race of cockleburs extends through 
three generations, beginning in 1909, at which time the original parent 
was discovered growing in a corn field, by a farmer living near Onaga, 
