1909] STEVENS & HALL—VARIATION OF FUNGI 9 
growth and much branching gives many narrow zones, rapid lineal 
growth with infrequent branching causes few broad zones. 
SCLEROTINIA LIBERTIANA FUCKEL, FROM LETTUCE 
Zonal sclerotial formation is exhibited by this fungus (fig. 8). That 
this phenomenon may be attributed to crowding of the mycelium is 
indicated by the fact that adjacent colonies form more sclerotia at 
their points of contact (jig. 9). 
Fic. 8.—Sclerotinia Libertiana Fuck., showing 1 f tion of sclerotia on corn- 
meal culture. 
SUMMARY REGARDING DENSITY OF MYCELIUM 
Zone formation in Ascochyta Chrysanthemi is due to crowding of 
mycelium, not to light or heat relation. A similar conclusion was 
reached by IstvAnFrFi® regarding the very striking zones shown by 
Sclerotinia. ‘The same cause may apply also with Daldinia concen- 
irica and many other fungi of similar structure. 
