1921] 
MATSUMOTO—SPECIALIZATION IN RHIZOCTONIA 11 
The shape of the sclerotia of the various strains will be more 
clearly demonstrated by the accompanying figures (figs. 1-3). 
INFLUENCE OF TEMPERATURE 
Studies on the temperature relations of parasitic fungi are 
numerous. The experiments and observations alike demon- 
strate that the growth of a large number of organisms may be 
closely related to relatively narrow limits of thermal conditions. 
There are many diseases which develop and spread only during 
relatively cool seasons, while on the other hand, there are numer- 
ous cases which develop only during the hottest weather of sum- 
mer. 
Confining the discussion to parasitic species we shall pass 
without comment the important work of Wiesner, Tiraboschi, 
and Thiele. Schneider-Orelli (’12) reported temperature studies 
on different species or strains of Gloeosporium fructig , and 
found that the European form had lower optimum, maximum, 
Fig. 3. a, sclerotial and hyphal cells of H; b, sclerotial and hyphal cells of B3; 
c, sclerotial and hyphal cells of the reisolated strain of B1 (camera lucida drawings). 
and minimum temperature than the American form. At 5°C. 
the European form produced a colony 0.4 cm. in diameter in 
12 days and a colony 3.7 cm. in diameter in 35 days, while 
the American form had made no growth at the end of 35 days. 
Brooks and Cooley (’16) noticed that the temperature re- 
sponses of the various fungi may be greatly modified by the 
food material upon which they are grown. Fusarium radicicola 
and Glomerella cingulata had a lower minimum temperature on 
corn meal agar than on fruit, and the early growth of species of 
