BIOLOGIC SPECIALIZATION IN THE GENUS SEPTORIA 
II 
Especially favorable conditions were also provided in order to infect 
Sonchus asper; still the transfer of the fungus to this more distantly related 
host was not difficult, for almost 25 percent of the inoculated leaves were 
more or less diseased. Such infection raises a question of identity between 
Septoria lactucae and certain of the species of Septoria described upon the 
Diagram 2. Infections with Septoria lactucicola from Lactuca canadensis. 
genus Sonchus. An examination of exsiccati showed a close similarity 
between S. lactucae and S. sonchifolia, but more extensive data is needed 
to prove their identity. The spots formed upon Sonchus asper by S. 
lactucae were grayish-brown to black, angular in outline, i mm. to 5 mm. 
in width, and contained reproductive bodies. 
Diagram 3. Infections with Septoria lactucae horn Lactuca sativa and Lactuca scariola. 
