Mar. 3,1933 
Origin of the Central and Ostiolar Cavities in Pycnidia 745 
BLACKROT FUNGUS OF DEWBERRY 
There is a blackrot fungus of dewberries the pycnidia of which are 
very similar to those of Phyllosticta paviae t P. labruscae f and P. solitaria. 
Pycnidia frequently develop on berries from North Carolina found in 
the New York and Washington markets. It requires but a short time 
for the black rot to make its appearance if berries are placed in damp 
chambers. On account of the slowness with which the disease develops 
in transit and market it will probably not prove of much economic 
importance. 
The fungus has not been connected with its perfect stage, but it may 
very well belong to Physalospora carpogena Atkinson, authentic speci¬ 
mens of which apparently are not in existence. The pycnidial stage 
has therefore been called by Shear Phyllostictina carpogena y and a formal 
description is to be published. 
The fungus has been isolated, and pycnidia have been grown to ma¬ 
turity on agar media. Dewberries artificially infected with spores from 
these cultures have developed the typical blackrot. An abundance of 
material from natural sources and from these cultures has been avail¬ 
able for study. 
FORMATION OF THE CENTRAL CAVITY IN THE PYCNIDIUM 
The “gnarl of hyphae” develops into a plectenchymatous body which 
has been called a “ pycnosclerotium ” (PI. 1, A), such as has been noted 
and described many times by those who have studied the blackrot of the 
grape. The large outer cells appear dark in color with thick walls, but 
toward the center the cell walls are very thin. The central portion pos¬ 
sesses sufficient food for future structural growth processes. While in 
this fungus, as well as in that of grape blackrot, it is undoubtedly true 
that similar bodies are immature spermogonia, or young perithecia, there 
can be no question that every pycnidium of both species passes through 
some such form in its development. If cavity formation for some very 
definite reason begins early, while the primordium is still plastic, then 
the resemblance to a “sclerotium” is not so marked. These bodies are 
frequently as large as mature pycnidia. If in such case there is little 
further enlargement, how may we account for the central cavity of the 
pycnidium? In the sections shown in Plate 2, A, B, and Plate 1, B, 
there is evidence of the beginning of disorganization of cells at the center. 
As soon as one or two cells disintegrate sufficiently, the surrounding ones 
push into the mucilaginous matter and in their turn begin to disorganize. 
It may be that degeneration is at first due to the head-on thrust of cells 
pushing inwardly; but, if one may judge by what follows, it is more likely 
that the breaking down process begins first. 
The cells of the next succeeding layer to push into the small open space 
present the appearance of rather thick sporophores, which is misleading 
(PI. 2, C, D; 1, C), since ordinarily these also become disorganized by 
degrees, and the cells below them push out in their turn. The wall 
layers are not as yet well organized. The conditions in this stage are 
shown in Figure 1, a. The cells lining the cavity clearly result from the 
budding or division of the cells of the original pseudoparenchyma. They 
do not show in this section very decided effects of pressure from within, 
such as Bauke ( 2 ) says results in crushing and flattening the inner-wall 
cells. Later, as the cells elongate or even divide tangentially, this 
