THE PROBABLE NON-VALIDITY OF CERTAIN GENERA 329 
E.) Taub. may possibly be the same as L. theobromae. From the 
above studies, Diplodia tuhericola is seen to differ from L. theobromae 
in the following manner: Diplodia tubericola as already stated, pro- 
duces pycnidia throughout all parts of the infected sweet potato 
(fig. 16). Moreover, the pycnidia while hirsute are often sparingly 
so. In L. theobromae there are few or no pycnidia in the interior 
of the host, and the pycnidial necks are strongly hirsute (fig. 23). 
Diplodia gassy pii is also distinct from the above two species, as will be 
seen by comparing figures 20, 21, 22 with figures 14, 17, and 19. Sup- 
ported by the above studies the genus Diplodia includes the char- 
acteristics upon which these other genera, viz. ; Chaetodiplodia, Lasio- 
diplodia, Botryodiplodia, and Diplodiella are based, hence, following 
the rule of priority, they are not tenable, and all the species in these 
genera become species of Diplodia. Further work will probably show 
that the genera Rhynchodiplodia and Pellionellia may likewise be 
referred to the genus Diplodia. The following is a somewhat broad- 
ened description of the genus Diplodia: 
Diplodia Fries. — Pycnidia black, subcutaneous to erumpent or 
superficial, scattered or in groups, csespitose or in a stroma;' hirsute or 
glabrous, paraphyses present or absent, spores hyaline, one-celled 
when young but one-septate, brown to dark when mature. 
Summary 
Inoculations with two species of Lasiodiplodia and two species of 
Diplodia have brought out the following facts: The genus Diplodia is 
very variable. The fungus Diplodia gossypii for instance, when in- 
oculated on the sweet potato, will show all the characteristics of the 
supposed genera Lasiodiplodia, Chaetodiplodia, Botryodiplodia, and 
Diplodiella. The same is also true when the Lasiodiplodias are 
inoculated on the sweet potato. From this it is therefore concluded 
that because of its priority the genus Diplodia alone should be retained, 
while the genera Lasiodiplodia, Chaetodiplodia, Botryodiplodia, and 
Diplodiella are not tenable and their species should be placed in the 
genus Diplodia. It is very probable that further work will show^ the 
necessity of abolishing the genera Rhyncodiplodia and Pellioniella. 
It seems probable also that more work will further reduce the large 
number of species of Diplodia. 
Slides of sectioned and stained material illustrating the above 
studies will be deposited at the Delaware Agricultural Experiment 
