756 
Journal of Agricultural Research 
Vol. XXIII, No. 9 
straminea there is a characteristic intercalary growth of orientation 
before any disorganization sets in. When a weak point is once established 
and an initial lysigenetic cavity formed, then growth readjustments can 
come into play, as the results of which the structure may increase in 
size by the elongation of elements already present at the end of the first 
period of growth. Intercalary growth in the wall is stimulated, and new 
cells may be added to the exterior. 
P Bauke found that in the pycnidium of Cucurbitaria the primordium 
was often as large as the mature fruit body; therefore, to account for the 
cavity he supposed that the sporiferous layer was pressed outwardly 
against the intervening parenchyma so that its cells were crushed. The 
ultimate effect of pressure due to disorganization is certainly a factor 
to be recognized, but it is very doubtful whether the cells referred to are 
crushed to the extent claimed. Those just outside the sporiferous layer 
are frequently small and flat, due to division, and are not the crushed 
remains of the large cells once at this point in the primordium. This is 
quite evident, for a study of Bauke ( 2 , fig. 12 and 13 of PI. IT), will show 
that the cells in the tissue said to be crushed must have undergone 
division in the process, for the ratio of the number of cells in the periphery 
of the primordium shown in his Figure 12 to the number in the layer 
beneath the sporiferious layer is as 3 to 2, while in the mature pycnidium 
shown in his Figure 13, this ratio is as 2 to 3. Bauke ( 2 ) and Baccarini 
(5, 6) both state that in old pycnidia sporophores disappear entirely, 
and many pycnidia have been formally described by authors as without 
sporophores. The writer has shown that the first hyphae to grow into 
the initial cavity are not necessarily spore bearing, though they are 
homologues of sporophores. In Phyllostictina carpogena the number of 
sporophore mother cells increases by multiplication of cells, by radial 
division, or by budding, while in Sclerotiopsis concava and Schizoparme 
straminea the sporophores increase by branching or budding of cells in 
the dome-shaped fertile tissue. Every cell in the thin-walled central 
region is potentially sporogenous. Sporophores are often sufficiently 
marked to be diagnostic, but that they are constant or permanent 
structures is not borne out by the facts learned from a study of these 
intermediate stages. That the sporogenous tissue by nature is funda¬ 
mentally different from every other in the primordium and that, once 
set apart in the early ontogeny, it remains a permanent, unchanging 
reproductive tissue is an idea probably carried over from zoology. 
Whether the contour of the sporogenous tissue is at all determined 
by the particular method of cavity formation may be very doubtful, 
but it so happens that the fertile tissue of the Phyllostictina blackrot of 
dewberry is strongly concave in outline; in Sclerotiopsis concava the 
incipient or potential spore tissue is convex, but by further disorganiza¬ 
tion and growth readjustments it soon becomes flattened out so that it 
forms an even layer extending across the base of the broad flat pycnidium; 
in Schizoparme straminea the fertile layer is sharply convex. It has been 
shown that in the first species the central cavity is largely lysigenetic. 
The cavity contains now a mass of predigested food readily available 
for spore formation, and it should be borne in mind that the fungus 
provides a large amount of food for this work when the fundamental 
tissue is developed so that in this pycnidium it is not necessary that 
more should be drawn from the vegetative hyphae. In Sclerotiopsis con¬ 
cava the central cavity is perhaps about equally lysigenetic and schizoge- 
netic. It is formed in much the same way as it is in the deep-seated 
