Mar. 3,1923 
Origin of the Central and Ostiolar Cavities in Pycnidia 755 
buffer tissue developed through which a passageway is opened, a wall 
organized, an ostiolar opening through the wall portions broken down, 
and a beak developed. The fungus must be able to organize a number 
of varied localized changes and growth processes harmoniously inter¬ 
acting in such a way as to lead to the construction of a fruit body with 
certain constant diagnostic morphological features. Such a structure, 
die cavities or openings in which are formed purely schizogenetically, 
is difficult to conceive. 
As Schizoparme straminea is found in nature there is nothing to suggest 
the presence of a stroma, except perhaps the buffer tissue ramifying 
through the host tissues and bursting forth, crowning the pycnidium. 
As explained, this tissue is formed after the knot of undifferentiated 
primordial hyphae has reached considerable size. Only one pycnidium 
grows from each knot of hyphae. On agar, however, several pycnida 
may arise from one of these masses of plectenchyma in such a way as to 
suggest that the line separating such pseduoparenchymatous primordia 
from true stromata is not to be too sharply drawn. Again, cavity 
formation may be started at several different points, followed by a 
merging of the locules, so that the cavity is at first much lobed or irregular; 
it finally becomes rounded out by further disorganization readjustments. 
A multilocular pycnidium would be a very simple step in the evolution 
from such a type. 
As noted previously, there is only a relatively small amount of destruc¬ 
tion of tissue during the formation of the central cavity. The ring 
lining the cavity (PI. 4, J; 6, F) represents practically all of such disor¬ 
ganization that occurs as the fungus grows on species of Rhus or Quercus. 
Ostiole formation is usually not begun until the central cavity is dis¬ 
tinguishable (PI. 4, B and E), but no set rule seems to be followed. 
Ordinarily the first spores are matured before the ostiole is completed. 
Figure B shows a section in which the position of the ostiole is already 
detennined by the disorganization of cells. The section (E) shows the 
proliferation of cells of the wall of the pycnidium and the enlargement 
and disorganization of cells of the buffer tissue. 
Fuisting (r) pointed out how difficult it was to find the early stages of 
perithecia which he was studying because there is nothing to indicate 
where they are forming until the Aperturalgewebes bursts through the 
host tissue, and by that time the perithecium is nearly mature. The same 
difficulty is encountered in connection with both perithecia and pycnidia 
of Schizorparme straminea as the buffer tissue is not visible until after 
the first steps in cavity formation have been taken. 
DISCUSSION 
Partly developed pycnidia of the type found in Phyllostictina carpogena 
have been considered by some authors to be merely young or undeveloped 
perithecia, especially when they are found in cultures. Some fungi 
develop vegetatively very well under artificial conditions and even reach 
the first stage in pycnidium formation to the extent of laying down the 
plectenchymatous primoridum, yet lack the particular stimulus which 
sets in motion the metabolic activities initiating the intermediate stages 
of growth which are fundamentally more complicated than the mere piling 
up of food in the form of undifferentiated tissue of the primordium. 
Very often cell destruction is accompanied with much swelling, which 
may not be without effect in stimulating further action. In Schizoparme 
