Feb. i6, 1920 Temperature Relations of Potato-Rot Fungi 



519 



The initial growth after the first 24 hours was noted always either at 

 the optimum point alone or at the optimum point and at one or two lower 



DIAMETER OP COLONIES IN MILLIMETERS. 



J" 75 AS- ^o ^s jb js fo^c. 



Fig. v. — Graph showing the rate of growth of VerliciUium albo-atrum No. 426 on potato agar at difierent 



temperatures. 



or higher grades of temperature, but never exclusively at any point other 

 that the optimum temperature (fig. i-8). 



Comparing the foregoing results of the temperature studies with the 

 geographical distribution of the fungi, we find that the parasites prevailing 



DIAMETER Ot COLONIES IN MILLIMETERS. 



S , /'O 7s 20 2S Jo JS 'fO "C. 



Fig. 8. — Graph showing the rate of growth of Verticillium albo-airum No. 427 on potato agar at different 



temperatures. 



in northern sections of the country (Ftisarium coeruleum and Verticillium 

 albo-atrum No. 427) have comparatively low maximum and low optimum 

 points; those from central zones (F. eumartii and V. albo-atrum No. 426) 

 exhibit a higher maximum, although they still retain practically the same 



