Mar. i7,1923 Influence of Soil Temperature on Seedling-Blight 845 
SPORE GERMINATION 
Conidia from several different strains of Gibberella saubinetii were 
germinated in the Altmann incubator and temperature chambers re¬ 
ferred to under methods, at temperatures ranging from 4 0 to 36° C., in 
hanging drop cultures of distilled water, soil decoction, and potato- 
dextrose agar, as well as on poured plates of potato-dextrose agar, and 
on young wheat seedlings growing in sterile, moist soil. The influence 
of temperature on rate and percentage of spore germination is shown 
for one medium, distilled water, in Table II. 
Table II .—Influence of temperature on the germination of conidia of Gibberella saubi¬ 
netii in hanging drops of distilled water 
Mean 
temper¬ 
ature. 
Average germination and length of germ tube. 
6 hours. 
24 hours. 
48 hours. 
96 hours. 
Germi¬ 
nation. 
Length. 
Germi¬ 
nation. 
Length. 
Germi¬ 
nation. 
Length. 
Genni- 
nation. 
Length. 
°C. 
3-6 
11. 0 
17. 0 
28. 5 
35 -o 
Per cent 
O 
O 
94 
97 
84 
O 
O 
IOO 
IOO 
40 
Per cent. 
O 
80 
M 
O 
75 
Per cent. 
86.5 
' 
0 
IOO 
Per cent. 
88 
f* 
45 
The results show that germination and growth take place over a wide 
temperature range. The cardinal temperatures for germination and 
growth of the germ tubes were not greatly altered by the use of other 
media than those given in Table II. The inhibiting influence of the ex¬ 
treme temperatures, however, was more marked in unacidified media. 
The optimum temperature for both rate and percentage of germination 
was raised about 4°C. by acidifying the potato-dextrose agar with one 
drop of 25 per cent lactic acid in each tube of agar. Good germination 
was obtained from 4 0 to 32 °, but above this temperature the conidia 
became very much swollen, with much thickened walls and twisted, 
abnormal germ tubes. 
The temperature range for ascospore germination was found to be 
essentially the same as that for the conidia. 
vegetative development 
.Potato-dextrose agar, both acidified and unacidified, was poured into 
Petri dishes, care being taken to have dishes of the same size and the 
same quantity of agar in each plate. A dilute conidial suspension was 
prepared, and a single loopful was placed in the center of each plate for 
the series started from conidia. Disks of equal size were cut from the 
outer circumference of a young colony on agar and placed in the center 
of the plates for the series started from mycelium. These plates were 
then incubated in a saturated atmosphere in the temperature chambers 
previously described under methods, at temperatures ranging from 8° 
to 36° C. and in the Altman incubator at temperatures ranging from 4 0 
to 30°. The rate of growth was determined by measuring the diameter 
