Jan. io, 1914 
Twig Blight of Quercus Prinus 
345 
Usually the germ tubes are sent out from the long axis of the spores 
(fig. 5, A and B) and occasionally from the sides (fig. 5, C). As many as 
six tubes have been observed from a single spore. 
At first the tubes * 
are nonseptate, but 
the cross walls grad¬ 
ually begin to ap¬ 
pear in from two to 
five days from time 
of germination. The 
hyphae show a 
marked tendency to 
coalesce (fig. 6), and 
often unite to form meshes. Soon after the formation of septse the 
mycelium begins to darken, taking on a grayish green hue. The hyphae 
become constricted, and peculiar chlamydosporelike bodies are formed 
(fig. 7) intercalary in the hyphae. When 
a number of spores are sown at one 
time, some of them undergo a further 
development, instead of germinating as 
above described. The spore turns a dark 
olive brown in color, and a central, transverse septum is formed. Occa¬ 
sionally two septae are present (fig. 2, C), but this is not typical. 
Fig. 6 .—Diplodia longispora: A portion of mycelium showing the coalescing 
of the hyphae. 
Fig. 7 .—Diplodia longispora: A portion of my¬ 
celium with chlamydosporelike bodies. 
DETERMINATION OF THE FUNGUS 
In order to determine definitely whether the Macrophoma and Diplodia 
types of spores were really stages in the life history of the same fungus, 
a number of single spores of each were planted in agar plates, and carefully 
marked colonies of each from single spores were then transferred to corn- 
meal flasks. Each first produced the Macrophoma stage and later the 
Diplodia stage. Numbers of diseased twigs were brought in from the 
field and carefully examined the following winter after being attacked, in 
the hope of finding a perfect stage, but without success. According to 
Saccardo, this fungus should be called a Botryodiplodia, as the pycnidia 
are usually grouped. However, since the characters which separate it 
from the genus Diplodia may be produced artificially on culture media 
and vary with the amount of moisture present, it seems advisable to 
place it in the latter genus. 
A number of species of Diplodia have been described on Quercus, 
mostly from European countries. All of them are described either from 
the immature stage, or insufficient morphological characters are given for 
a positive identification, the spore measurements in several being absent. 
Only one species has been found described from America —Diplodia 
longispora C. and Ell. on Quercus coccinea from New Jersey. It is the 
