346 
Journal of Agricultural Research 
Vd. I, No. 4 
only species which is described with mature spores and in which the 
spore measurements are given. The morphological characters given 
agree very well, but, according to the measurements given, the spores 
are uniformly longer and narrower, being 30 to 35 by 7/z in comparison 
with 23 to 32 by 8 to 1 2/j. of the species under discussion. 
However, since there is much variation in this genus and since the 
perfect form of this fungus may eventually be found, the species herein 
described is referred to Diplodia longispora C. and Ell. While, as men¬ 
tioned above, the spore measurements do not exactly agree, the variation 
being considered by some sufficient to warrant a new species, it was not 
thought desirable to add another species to the already cumbersome 
and much confused nomenclature of this genus. None of the species 
described are recorded as causing any disease of the host. 
SUMMARY 
A fungus which is referred to Diplodia longispora C. and Ell. is the 
cause of a destructive twig disease of Quercus primes, also of several other 
species of Quercus and of Castanea dentata. 
Large trees are not killed outright, but they may eventually die as a 
result of the weakened condition caused by losing the young branches, 
and particularly the cumulative effect of the attacks of several years. 
Saplings are often killed outright. 
Infection takes place through wounds in the bark and will not take 
place through an unbroken surface. The fungus does not extend into 
the leaves, as no mycelium is present in the leaf tissues. 
DESCRIPTION OF PLATE 
Pirate XXXVIII. An oak (Quercus gambelii) inoculated with Diplodia longispora 
at X when dormant. No leaves developed above the point 
of inoculation. 
