578 BULLETIN 347 
the winter months. Fresh spore horns are not seen during the winter, 
but this may be due to the fact that they are produced at such a slow _ 
rate that they are washed away before their size makes them noticeable. ” 
Development of perithecium.— The beginning of the perithecial stage 
is accompanied by a marked increase in the size of the stroma, which now 
pushes off more of the cork layer and not only fills up the enlarged rent 
but also grows out over the torn edges so that they are included in it 
(Fig. 85, page 558). The stroma takes on an erumpent, superficial appear- 
ance (Plate XXXVII). This change has been observed within eight 
weeks after inoculation; on trees inoculated in June the stromata have 
been found in August. 
Fic. 93.— Stages in the development of the carpogonium. The larger, heavily shaded cells 
at the center are the ascogonial cells, with the cells of the enveloping hyphx about them. 
The last figure shows the continuation of the ascogonium into the trichogyne. All figures 
are drawn to the same scale 
The primordia — beginnings of the perithecia — arise in the base of 
the stroma or even among the outermost cells of the host. Each prim- 
ordium consists of two to five large, prominent cells arranged in a circle 
or a spiral (Fig. 93), closely invested by a sheath of large hyphe. The 
central prominent cells form the ascogonium, and the investing hyphe 
will here be called the envelope. The ascogonium, which is an enlarged 
single hypha, is continued up to the surface of the stroma as a prominent 
thread, the trichogyne. There may be as many as a hundred primordia 
in a single stroma, but only about one fourth of them ever reach maturity; 
the others degenerate at various stages of development. 
The ascogonial cells are elongated-oval, slightly curved so as to fit 
the segment of the spiral, deeply constricted at the septa, and only loosely 
