Culture of Verticillium albo-atrum , B. et Br. 525 
^ 4°? 2 5? 2 °? 2 5? 45? 4°? 35? 3°? 3°? 45? 45? 35? 4°? 45? 5 C ? 55? 6o, 6o, 45? 4°? 5°’ 6o, 35? 4°? 
2§ ? 35 ? 4°? 45? 65, 6 5? 2 §? 45? 5°? 35? 4°? 3 8 ? 45? 55? 4°? 55- Average, 43 = 86 ft. 
2o°C.—65, 60, 80, 65, 65, 70, 55, 85, 80, 75, 80, 60, 75, 80, 85, 45, 50, 90, 90, 85, 65, 75, 70, 85, 
60, 60, 70, 80, 85, 95, 90, 75, 60, 65, 80, 75, 55, 40, 45, 62, 38. Average, 72 = 144 n. 
22 , 5°C. —64? 80, 95, no, 120, 65, 70, 80, 90, 80, 85, 60, 80, 80, 60, 50, 125, 100, 75, 120, 80, 75, 
80, 100, 65, 85, 90, 100, 55, 60, 80, 70, 75, 65, 95, 90, 130, 68, 70. Average, 82 - 164 //. 
2 5 C. 30, 35? 4°? 45? 45? 3°? 35? 3 2 ? 45? 45? 5°? 4 °? 35? 4 °? 45? 3 °? 35? 4°? 45? 60, 65, 45, 50, 35? 
5 °? 5 °? 45 ? 45 ? 3°? 35 ? 45 ? 5 °> 4°? 45 ? 4°? 5 °? 75 ? 60, 70, 45, 50. Average, 45 = 90//. 
27°C.—6, 30, 18, 13, 6, 10, 8, 8, 6, 6, 10, 8, 13, 16, 18, 6, 6, 8, 10, 8, 8, 10, 6, 13, 18, 10, 13, 8, 
16, 6, 6, 6, 6, 8, 8, 11, 16, 18, 10, 8. Average, 10 = 20^. 
Edson and Shapovalov (2), in their experiments to determine the growth 
of various fungi at various tempera¬ 
tures, found for V. albo-atrunt an 
optimum at 25° C. They incubated 
the fungus at io°, 15 0 , 20°, 25 0 , and 
30° C. If, however, they had experi¬ 
mented with smaller differences of 
temperature, as has been done in 
this paper, the optimum might have 
been found to be between 20° and 
25 0 C. or between 25 0 and 30° C.; 
and the growth at the real optimum 
might have been considerably greater 
than that found at 25 0 C., which was 
arbitrarily assumed to be the op¬ 
timum. 
Fig. 4. Photograph showing the difference 
in the amount of mycelial ‘ spread ’ due to differ¬ 
ence in thickness of the medium, that on the 
left hand being the thicker. It also shows the 
It may be mentioned that with difference in zonation producedI by the difference 
J m thickness. Incubated at 25 C. 
the fungus here investigated the maxi¬ 
mum varied with different food material, as will be described later on, but 
the optimum always remained the same. 
Edson and Shapovalov determined the optimum by measuring the 
spread of the fungus on solid media. It should be pointed out, however, that 
with this method great care must be taken that the thickness of the medium 
is constant ; for the spread of the fungus varies with thickness unless the 
medium is very thick, i.e. about 10 mm., in which case a little difference 
does not affect the growth. Fig. 4 shows a photograph of halves of two 
plates containing media, 4 and 6 mm. thick respectively. The difference 
in size of the fungal growth is well marked. 
It was found that V. albo-atrum could under no circumstances with¬ 
stand 33 0 C. for one week. An attempt was therefore made to discover how 
long it could withstand high temperatures. The period was gradually 
decreased and various food materials used. It was found that the lethal 
temperature varied with different media. Thus with potato-mush agar, pea- 
broth agar, Dox agar, corn-meal agar, and cooked banana exposed to 33 0 C. 
M m 
