748 
Journal of Agricultural Research 
Vol. XXIII, No. 9 
There are eight pycnospores in the spermogonium, a section of which 
is shown in Plate i, G. There is now no evidence of the origin of 
these spores, which were probably formed at an early stage in cavity 
developement; and the cells from which they were derived have now 
disappeared. The writer has not seen sporophores in those spermogonia 
of Guignardia bidwellii, which contain a few pycnospores. 
It has been shown above that spermogonia and pycnidia are formed 
from bodies similar to what Reddick ( 8 ) calls “pycnosclerotia.” In 
many species the tissue composing the “gnarled” primordium is not at 
all sclerotized. Pycnidia of Schizoarme straminea Shear, for example, 
arise out of a tissue that can not be distinguished from a stroma (PI. 4, A). 
The very irregular tuberculate and massive forms taken by the “ pycno¬ 
sclerotia” of Phyllostictina carpogena in cultures on agar very frequently 
become arrested at this point, but so many have been found in the 
process of cavity and spore formation as to suggest that these structures 
are fundamentally sclerotized stromata, out of which, or in connection 
with which, fruit bodies are formed. Pycnosclerotia then, if we may 
put it that way, are not designed to be resting stages in the life cycle, not 
necessarily structures into which the fungus is forced (even if frequently 
compelled to remain there) by unfavorable environmental conditions. 
They are the result of a regular and natural course of events by which 
■wtaiti quantities of food and fungous tissue are brought together in 
preparation for spore formation. Having seen that in this Phyllostictina 
there is little actual crushing of tissue such as was thought by Bauke (2) 
to be the case, the relative importance of the two factors, disorganization 
and growth inequality, in cavity formation can be judged also by the 
little average difference in size between the “pycnosclerotia” and mature 
pycnidia. Allowing for cases such as were noted previously in which 
cavity formation begins very early, the central cavity in this species 
is ordinarily, then, largely lysigenetic. We may next turn to a pycnidium 
of an entirely different type. 
ORIGIN OF THE CENTRAL CAVITY IN THE PYCNIDIUM OF THE STRAW¬ 
BERRY-ROT FUNGUS 
Associated also with the rots of dewberries and strawberries is the 
fungus, Sclerotiopsis concava (Desm.) Shear and Dodge, and its conidial 
stage is very common on other plants ( 12 ). The pycnidium is large, 
shield shaped, and without ostiole. The big spore cavity is surrounded 
by a heavy brown wall several cells in thickness and at maturity is 
densely packed with spores (12, PI. 5, Fig. 17). 
The intermediate stages in development are best studied from sections 
of material grown on strawberries or on infected leaves placed in damp 
chambers. In the younger primordia, hyphae invade the epidermal 
cells, bursting through the side walls and lifting the cuticularized layers, 
forming a broad, compact, mound-shaped tissue (PI. 3, A), most of the 
outer portion of which consists of hyphae spreading outward from a 
broad base (PI. 3, B). The cells at the ends of these hyphae after a suc¬ 
cession of divisions become elongated peripherally. Now along a line 
5 or 10 cells from the outside border a narrow zone of degeneration can 
be distinguished; cells are losing their contents and elongating as though 
under strain (PI. 3, C). This disorganization occurs in intercalary 
cells shown at the right in the figure. The line of rupture is not neces¬ 
sarily so evenly curved that it follows the contour of the outer wall; 
