THE PROBABLE NON- VALIDITY OF CERTAIN GENERA 327 
Dilution cultures carefully made of the Macrophoma spores pro- 
duce a growth typical of Lasiodiplodia tubericola, and when inoculated 
on the sweet potato produces the typical Java black rot. Similar 
conclusions have been reached by Emerson (7) and several others. 
According to Jonge and Dorst (13), Lasiodiplodia theobromae on cocoa 
emits from its pycnidia white, strongly curled tendrils made up of 
hyaline one-celled spores of the Macrophoma type. As alreadys een, 
this same fungus on the sweet potato produces only the Diplodia type 
of spores. This clearly indicates the influence of the host as a factor 
in promoting or suppressing the Macrophoma stage. 
In order to study further the relationship of the genera here under 
discussion, sweet potato material infected with the above fungi was 
fixed in a chrom-acetic solution of medium strength, then sectioned 
and stained with safranin and gentian violet. It is only through a 
pathological study of the host infected with these fungi that the 
relationship of the supposed established genera is brought to light. 
As already stated, when sweet potatoes are inoculated with the fungus 
Lasiodiplodia tubericola, pycnidia are produced with or without para- 
physes (figs. 14 and 15). The same also holds true for Diplodia 
gossypii on the sweet potato, i. e., there are many pycnidia with and 
without paraphyses. 
A study of the sectioned material further reveals the fact that some 
of the pycnidia of Lasiodiplodia tubericola on the sweet potato are 
either borne singly or in groups (fig. 15), and seem to be embedded in 
a stroma (figs. 14 and 19). This also holds true for Diplodia gossypii 
on sweet potato. It will be remembered that Diplodia and Lasio- 
diplodia differ in that the latter possess paraphyses and the pycnidia 
are embedded in groups in a stroma; Diplodia has no paraphyses and 
the pycnidia are borne singly. This at once shows how artificial 
is the separation of these two genera. Diplodia gossypii in the sweet 
potato produces paraphyses (fig. 21) and the pycnidia are either borne 
singly or in groups (figs. 22 and 26), as is the case with Lasiodiplodia 
tubericola. Because of these facts we are justified in dispensing with 
the genus Lasiodiplodia. Jonge and Dorst (13) reached a similar 
conclusion in their work on the fungus Lasiodiplodia theobromae as 
did also Griffon and Maublanc (10). 
It has already been stated that Chaetodiplodia is distinguished 
from Diplodia in that the neck of the pycnidium is hirsute, whereas in 
the latter it is without hair, a distinction which is very artificial. 
