1896] CERTAIN PYRENOMYCETOUS FUNGI 321 
be caused quite as easily by insufficient nutrition as by lack of 
fertilization. 
About the time that fusion of the two gametes occurs, in 
normal cases numerous branches arise in the neighborhood of 
the young fruit and become intimately interwoven around the 
sexual organs to form the wall. Fora time the swollen archi- 
carp can be seen in the center of this knotted mass of sterile 
filaments, but as the wall thickens and the threads of which 
it is composed become more closely septate this interesting 
structure is lost from sight. For further steps in the process 
it is therefore necessary to refer to sections. To get very early 
stages it was necessary to fix the growing material before any 
sign of color appeared on the outside of the tiny rounded bodies 
which were just becoming visible in the mycelium. The rate of 
growth varied so much that no definite age could be established 
as the proper one for sectioning, and repeated trials were made 
before sections containing the desired information were secured. 
By means of a long series of observations it was at last deter- 
mined that in the stage just preceding the origin of the asci, the 
Perithecium consists of a spheroidal mass of cells of three kinds. 
First is an outer layer two or three cells thick of thick-walled, 
nearly isodiametric cells, made up of the sterile hyphae which 
envelop the young sexual organs. Inside this is a layer, two 
to three cells in thickness, of tabular cells which appear to have 
been laterally compressed by growth from within. These two 
have evidently been formed from the enveloping hyphe. The 
center of the sphere is entirely filled with loose, spongy tissue 
composed of parenchymatous cells, well filled with protoplasm. 
These cells show no differentiation of form, and nothing exists 
= indicate where the asci will originate save that in certain sec- 
‘ie small group of these cells, lying about midway between 
enter and circumference of the spongy tissue on one side, 
ene a slightly deeper strain. Even in the very young age? 
Sa : the sexual organs imbedded in the spongy oui 
is ound. It is at this point that De Bary and gest 
iged to leave gaps in their records of perithecial deve 
