326 
Journal of Agricultural Research 
Vol. I. No. 4 
The cross-inoculations upon the apple, carried simultaneously with 
infections by the apple bitter-rot fungus, show that the pecan fungus 
from both leaves and nuts is at least physiologically similar to the Glom- 
erella of the apple. The morphological characters will be discussed 
later. 
Cultural Studies 
THERMAL TESTS 
Several series of corn-meal-agar cultures were grown for two to three 
weeks at temperatures ranging from i° to 35° C. As a result of these 
studies it was found that no growth would take place below 6°, either 
with freshly inoculated cultures or with those in which growth had already 
started before incubation. At 7 0 to 8° the growth was extremely slow, 
but gradually increased with rise of temperature until the maximum 
for the strains tested was reached at about 30°. 
cultural characters 
Since the fall of 1910 various strains of the fungus have been grown 
on the common culture media, and their appearance under different 
conditions is briefly given as follows: 
Beef-Agar Slant Tubes.—The colony first appears as a colorless, roundish, submerged 
mycelial mass which at ordinary temperatures generally covers the slant in five to 
seven days, while one to several groups of acervuli or black perithecia have in the 
meantime usually begun to form. The growth is at first entirely submerged and the 
surface of the slant presents a smooth glistening appearance. However, after some¬ 
thing like two weeks a small amount of whitish aerial mycelium makes its appearance 
toward the upper edge of the slant. In old cultures this subicle may sparsely cover 
the whole surface, while the submerged parts become very dark colored. 
Corn-Meal Flasks.—Growth becomes visible in two to three days as a roundish 
colony several millimeters in diameter, with sparse, white to pinkish, cottony aerial 
mycelium in which are usually scattered a considerable number of dark olive-brown 
dots. These dots are found to consist of numerous interwoven hyphae with swollen 
and contorted cells in process of uniting to form a pseudoparenchyma. These dark 
masses later develop either into acervuli or perithecia. 
Corn-Meal-Agar Slant Tubes.—The white to colorless growth is at first submerged 
or at the surface. After several days acervuli or perithecia usually begin to form 
and a scant whitish aerial mycelium may appear at the edges of the slant. The pink 
spore masses are often developed without the formation of a dark-colored stroma, 
while in other cases this stroma may be the most conspicuous part of the acervulus. 
The perithecia are developed within black carbonaceous masses of mycelium which 
may or may not be submerged in the medium. In old cultures parts of the submerged 
growth often become olive green to almost black. 
Cooked-Potato Cylinders.—Growth first becomes evident through a light-brown 
discoloration of the tissue immediately around the point of inoculation, and usually 
a whitish aerial tuft of mycelium appears within 24 hours at the center of the dis¬ 
colored area. This breaking down of the tissue progresses rapidly so that after several 
days the whole cylinder becomes involved. The white to pinkish cottony subicle 
develops somewhat more slowly, but eventually covers the cylinder and bears the 
embedded acervuli or perithecia.* 
