ORIGIN OF THE CENTRAL AND OSTIOLAR CAVITIES 
IN PYCNIDIA OF CERTAIN FUNGOUS PARASITES 
OF FRUITS 1 
By B. O. Dodge 
Pathologist , Office of Fruit-Disease Investigations , Bureau of Plant Industry > 
United States Department of Agriculture 
SCOPE AND PURPOSE OF THE INVESTIGATION 
An investigation of fungi associated with rotting strawberries and 
dewberries during shipment and marketing has afforded an opportunity 
for study of the development of the pycnidial form of several species of 
fungi, from which it appears that in these forms there are three principal 
stages or periods of growth. The first is one of rapid cell multiplication 
whereby a certain amount of fundamental or undifferentiated tissue is 
formed with which to begin the construction of the fruit body. The 
second or intermediate stage includes those activities leading to the forma¬ 
tion of the central cavity, the organization of the wall, the delimitation 
of sporogenous tissue, and, in many forms, the construction of the 
ostiole. Previous study has largely been confined to the third stage, 
which includes spore production and other developments which charac¬ 
terize the mature pycnidium. The methods by which the plectenchyma- 
tous primordium is formed are also fairly well understood, but just how 
the characteristic pycnidium is evolved out of the mass of undifferentiated 
tissue has not been clearly explained. The intermediate stages in the 
growth of phycnidia of several species have been followed by the writer, 
and the results of the studies on three of these are reported in this paper. 
Bauke’s contribution (2) 2 is noteworthy because of the clearness with 
which he describes the two different methods by which pycnidia originate; 
and on this point, which was his main contribution, his work has been 
repeatedly confirmed. From the very nature of the subject of his inves¬ 
tigation, the method which he employed was not adequate to give the 
best results. He found it difficult to learn what takes place in the 
pycnidial “knot” when the cavity is being formed and the sporiferous 
layer organized, as he was compelled to study the fungus as it grew on 
slides. In the pycnidium of Cucurbitaria elongata a cell at the center 
becomes divided into a few radially arranged pyramidal cells with their 
apices together at the center. These are the sporophores or their mother 
cells. They divide again in various directions or at once cut off spores. 
By the gelatinization of their walls, the sporophores are separated from 
each other to form the cavity, which is further increased by the swelling of 
the mucilage derived from the walls of the spores. In the pycnidium of a 
Diplodia on Cornus there is at the end of the first period of growth a 
1 Accepted for publication Oct. 22, 1921. 
1 Reference is made by number (italic) to “ Literature cited,” p. 758-759. 
Journal of Agricultural Research, 
Washington, D. C. 
abz 
(743) 
Vol. XXIII, No. 9 
Mar. 3, 1923 
Key No. G-284 
