1916] LINK—FUSARIUM 195 
It should be noted here that F. trichothecioides when Garitated 
into a tuber can grow at 30° C., while it cannot do so in arunein 
media; and that F. oxysporum can survive a temperature of 1° C. 
in artificial media, but not in the tuber. 
TABLE IV 
CONDITION OF TUBERS AT CLOSE OF EXPERIMENT 
Temperature Fusari Ysp Fusarium trichothecioides 
$0 Ges as Se All cone rotted; Slight rot in some 
sprou 
$e" Ge OV eehesee ee All completely rotted; All completely rotted; some 
: sprouts killed sprouts ki 
A fl PL RNS! he meme ri am All uh very slight rot All completely rotted 
Coys os yeaa aa No rot All with slight rot 
1° C. for two weeks, then 
525 ©: for two weeks. .| Slight rot in one tuber All completely rotted 
ie 0 rot No rot 
—r1° . for two weeks, then 
5° C. for two weeks. . No rot All completely rotted 
Discussion.—These results may, in part at least, explain why 
F. oxysporum, even though it can attack parenchyma and rot tubers, 
usually is not found in rotted tubers, while F. trichothecioides is. 
The ability of the latter to make a faster initial growth at the 
temperatures which prevail in the soil about digging time and in 
well kept storage places is probably the determining factor in this 
phenomenon. The experiments with tubers showed that F. éri- 
chothecioides made a great increase in growth rate when transferred 
from a low to a higher temperature. 
These temperature relations may also explain in part the fact 
that we usually find F. oxysporum producing wilt under field con- 
ditions, and lend support to the observations made by Orton (27), 
who reports potato wilt induced by Fusarium spp. to be pre- 
eminently a warm climate disease. F. trichothecioides can produce 
wilt, but the temperature conditions in the soil are such as to favor 
F. oxysporum, the maximum temperature of the former being 
the optimum of the latter. Humpurey (15), working in Washing- 
ton on the tomato wilt induced by F. oxysporum, came to the con- 
clusion that temperature differences in various parts of the state — 
were determining factors for the appearance and non-appearance 
and severity of the disease. 
