744 
Journal of Agricultural Research 
Vol. XXIII, No. 9 
pseudoparenchymatous structure of thin-walled cells bordered by a 
cortical region. Now at various points in the central portion there 
appear elliptical areas marked by inwardly growing hyphse. There are 
a number of these regions of growth corresponding to the number of 
locules which will appear in the young pycnidium; some of them may 
become united as the phycnidium ages. According to Bauke it is the 
head-on thrust of these young sporophores against each other and the 
pressure due to the gelatinization of their walls that accounts for cavity 
formation by forcing the sporogenous layer farther and farther out, 
crushing the tissue between it and the cortex so that the protoplasm of 
this crushed tissue can be used in nourishing the spores. 
De Bary (j), without referring to Bauke’s account, describes the 
development of the pycnidium of a species of Pleospora and says that 
the central cavity is due to the failure of the cells at the center of the 
pycnidial primordium to keep pace in their growth with those in the 
periphery so that the cells at die center are torn asunder. Such a cavity 
would be schizogenetic. 
Baccarini (5, p. 69) describes the formation of a cavity in Sphaeropsis 
malorum and adds a further note on the development of pycnidia in 
general (6, p. 750-151). Certain cells at the center of the pseudoparen¬ 
chyma can be distinguished from the rest by their abundance of oil 
and glycogen. Their walls become transformed into mucilage which, 
absorbing water, swells to form a central, oval, or spherical cavity lined 
with sporophore fundaments. This sporiferous layer plays an important 
part in the further development of the pycnidium. Baccarini does 
not say that the entire contents of the cells at the center disappear as 
the cavity is formed. His account is very similar to that given by 
Bauke, adding nothing except to state (6, p. 150) that lysigenetic and 
schizogenetic factors enter into the processes, depending upon the 
quantity of tissue present at the center of the primordium and on the 
rapidity with which it is reabsorbed. 
Reddick ( 8) studied the development of the pycnidium of blackrot of 
the grape. He states that the activity at the center of the “ gnarl” is 
evidenced by the more deeply staining contents of the cells. He finds 
that a number of hyphae grow inwardly and assumes that these are the 
young sporophores. He realizes that the cavity later increases in size, 
and he believes that it does so in some way at the expense of the pseudo¬ 
parenchyma. In his description of the origin and the development of 
the perithecia the nature of the “sclerotium” is discussed. He believes 
that such a body develops into a perithecium and gives it the name 
pycnosclerotium. 
Hesler (jo) describes briefly the development of the pycnidium of 
Sphaeropsis malorum. His account is similar to that given by Baccarini, 
to which he refers. Hesler, however, states without further comment or 
figures that the cavity is formed by the breaking down of cells and that 
the ostiole is formed in the same way. He is of the opinion that the 
dome-shaped tissue (often shown in figures of this pycnidium) from which 
the sporophores arise is due to irregularities in the cavity which is tend¬ 
ing to become multilocular. 
In order to best illustrate the relative importance of the two factors, 
disorganization and growth inequalities, in cavity formation, the inter¬ 
mediate stages in three pycnidia will be described. The formation of the 
ostiole will be considered in connection with one of the forms. 
