340 
Journal of Agricultural Research 
Vol. I, No. 4 
tracheary tubes and throughout the cells of the inner and outer bark. 
A study of the distribution of the mycelium in the twigs of different ages 
and the relative amount present in the wood and cambium of the dis¬ 
eased twigs was not undertaken. 
MORPHOLOGY OF FUNGUS 
Soon after the leaves wither on the affected twigs, small papillae begin 
to form under the bark, which in the course of a few weeks break through 
Fig. i .—Diplodia longispora: A section of a pycnidium. 
in the form of the small, black pycnidia mentioned above. These are 
globose to subglobose in shape, very distinctly ostiolate, and dark brown 
to black in color. In size they vary from 95 to 145^ in diameter. In 
cross section (fig. 1) the wall of the pycnidium is made up of practically 
two parts: The outer, dark carbonlike layer 
and an inner membranous layer of typical 
fungous cells. These cells have a decidedly 
purplish tinge, merging into hyaline as the 
s orogenous layer is reached. 
The spores both on the host and in culture 
are oval or ovoid (fig. 2, A) } often tapering 
somewhat at one end, densely granular, often Fig. 2—Diplodia longispora: stages 
Very thick-walled, averaging about 29 x Iljtt phoma stage; B t Diplodia stage; 
in size. At first the spores are hyaline and c * Diplodia spore with two 
continuous, but after some time (fig. 2, B) they septa * 
take on a yellowish tinge and finally become dark brown in color and 
1-septate. Rarely the septum forms in the hyaline spores before the 
color begins to change, but this is not usually the case. 
The spores are borne singly on rather short, broad conidiophores, 
interspersed with numerous filiform paraphyses, and are ab join ted from 
the tip at maturity by a constriction near the end of the conidio- 
phore. The conidiophores may become long and filiform in artificial 
media. The liberation of the spores from the pycnidium is effected in 
damp weather by means of distinct cirrhi, or threads, forced out through 
the ostiole of the pycnidium. 
