Apr. as, 1923 Species of Fiisarium Isolated from Potato Tubers 
353 
pown in the dark incubator and those grown in diffused light, but the 
lima bean is not a good color producer under any condition. 
With potato glucose agar there was some difference, though it was not 
striking. These comparisons were drawn, however, from cultures grown 
in the light incubator and others grown in the dark incubator (p. 350). 
Oiu: notes taken when the cultures were a week old show that in the 
dark group A produced rufous pseudopionnotes; in the light they 
were ferruginous. A more intense purple color showed in group D when 
grown in the light than when grown in the dark. The most striking 
comparison, in fact practically the only striking one, was in the case of 
culture No. 69 which produced carmine mycelium in the light and white 
mycelium when grown in the dark. 
Notes taken on a complete series of week-old cultures grown on potato 
glucose in diffused light showed practically the same results as those 
taken on the cultures grown in the dark incubator. 
Smith and Swingle (rp) found that often cultures which produced— 
a beautiful, rich salmon colored mycelium when grown in sunlight produced white 
mycelium when grown in a dark closet. 
A difference in color was not noted on all media tried. Except for a 
difference in color these men concluded that light had no material effect 
on the growth. 
Appel and Wollenweber (2) noted that conidia masses were much 
richer in color when grown in the light than in the dark. They also 
noted that when cultures were grown in the dark, poorly developed 
conidia with uneven septations and form appeared. Although direct 
sunlight was not exactly injurious the diffused daylight was most favor¬ 
able in every way for the product of morphological characters. 
EFFECT OF TEMPERATURE 
We did no work with the effect of temperature on the fungi, but a 
summary of the conclusions of other workers may be of value. 
In working with Fusarium oxysporum, Smith and Swingle (jp) found 
that the fungus grows well on boiled potatoes at a temperature of from 
15® to a little above 30*^ C. Below 15*^ the growth became slower and 
slower until 5° was reached, when practically no growth took place. 
Above no growth took place. 
Link (j j) did some detailed work on temperature relations of Fusarium 
oxysporum and F. trichothecioides. The optimum temperatures for the 
two are different. However, at temperatures between 15° and 20® C. a 
good growth was made by both. 
Lewis (ii) in his work with 24 cultures of Fusaria found that 20® 
to 25® C. seemed to be the best range of temperature for most of the 
cultures. 
Appel and Wollenweber (2) in their summary of conditions which will 
guarantee a ‘‘normal growth” say that room temperature should be 
used, that is, “between 12° and 25° C. neither higher nor lower.” 
Edson and Shapovalov (5), working on temperature relations of six 
of the more common species of Fusarium, found that growth took place 
in varying amounts between 2® and 38° C. The minimum for growth 
was shown by F. discolor var. sulphureum, the maximum by F. radioicola. 
The maximum growth for all cultures took place between 25° and 30®, 
though growth was abundant between 15® and 30°. 
