Mar- 3 .19 23 
Origin of the Central and Ostiolar Cavities in Pycnidia 753 
made first, after which disorganization spreads in several directions, and 
it is the outermost cells of the buffer tissue that are last broken down 
(PI. 4, D). The swollen cells of which it is composed contain very little 
cytoplasm; but there are certain regions in which they show signs of 
degeneration, accompanied by still further swelling, so that the hood 
becomes split or ruptured in a very interesting fashion, the lines of 
cleavage radiating from the point below at which the beak of the ostiole 
is being formed (PI. 5, D). 
The cells of the buffer tissue still possess the power of growing, for as 
soon as a cavity has been formed in it by disorganization small hyphal 
branches bud out (PI. 4, E). These branches are very soon entirely 
reabsorbed. 
By the time a passage way has been opened through the buffer tissue, 
other short hyphae have begun to appear from the wall cells, converging 
to form the beak of the ostiole. The cells lining the ostiole are certainly 
the homologues of periphyses, but in this case they usually disorganize 
so that in a fully mature fruit body (PI. 6, B) little trace of them remains. 
In the meantime the central cavity has become greatly enlarged, and the 
remnants of broken-down cells may be seen clinging to the inner wall, as 
noted above (PI. 4, J). It is interesting to find that in the ascocarp of 
this fungus (PI. 5, F-H) the host tissues are broken open by the same sort 
of buffer apparatus. This is disorganized in the same fashion and pene¬ 
trated by the ostiole in like manner; the periphyses are, however, more 
permanent (PI. 5, J). In the pycnidial cavity there is much more dis¬ 
organization of tissue when the fungus is grown on agar media where the 
absence of confining host tissues may be an additional reason for the 
delay in the differentiation processes. 
Other stages in the life history of Schizoparme straminea are illustrated 
in Plate 5. The habit of growth of pycnidia on the fruit of strawberry 
is brought out in Figure A, which is somewhat magnified. The buffer 
tissue which has broken through the epidermis of the host is the only 
part of the pycnidia visible. On agar media in Petri dishes the mycelium 
appears to break up into fan-shaped lobes, and the pycnidia form more 
or less in concentric circles (Fig. B). Surface views of pycnidia on agar 
such as are shown in Figures C and D bring out very strikingly the 
manner in which the buffer tissue splits open, frequently in the form of a 
cross. 
That the buffer tissue is composed of cells originating from the upper 
portion of the outer wall of a pycnidium is clear from the sections shown 
in Figure E. It is often difficult to distinguish perithecia from pycnidia 
by the appearance of the buffer tissue exposed, although the ascocarps 
are frequently much larger than pycnidia. Figure F shows a number of 
perithecia as they appeared on a much decayed leaf of Rosa sp., bringing 
out well the manner of splitting the buffer tissue, which is so character¬ 
istic of the tissue above pycnidia also (Figs. C and D). Mature asco¬ 
carps collapse when dry. Sections of a young perithecium through the 
papillate ostiolar portion (Figs. G and H) show that the buffer tissue 
evidently functions in rupturing the host tissue, although it soon dries 
up and falls off after bursting through the epidermis (Fig. I). It is 
clear from Figures I and J that there are no paraphyses between the 
asci, although falcate periphyses line the ostiolar cavity. A ma ture 
ascocarp with fragments of buffer tissue still adhering is shown in 
Figure K. 
