ENDOTHIA CANKER OF CHESTNUT 56r. 
are not typically curved is an additional reason why this stage should not 
be referred to Cytospora. The spore membrane is thin and smooth. 
The spores are filled with dense homogeneous protoplasm, and each spore 
contains a single small, elongated nucleus near the center. There is also 
a polar body in each end. 
Perithecia 
The mature stromata on older cankers have numerous projecting 
papillz on the surface (Plate XXXVIII, Fig. 2). The black speck 
at the tip of each papilla is the opening of a perithecium, the body 
of which is located down in the bottom of the stroma and is connected 
with the apex by a long, black neck. These papille may scarcely project 
above the surface of the stroma, or, on the other hand, they may be a 
Fic. 88.— Stages in the development of the perithecium 
a, Cross section at the stage when the cavity is occupied by young paraphyses. The neck 
is not shown . : 
b, Tip of the neck in cross section as it appears, pushing up through the stroma at the 
same stage as shown in (a) Byers ; : 
c, Lower part of neck and canal when the perithecium is almost mature, showing periphyses 
projecting into the canal 
millimeter or more in length. They are longer in moist, shaded places 
than in dry, lighter surroundings. There are commonly fifteen to thirty 
perithecia in a stroma, but the number varies greatly, over forty having 
been counted in some cages. In Fig. 85 (page 558) and in Plate XL, 
Figs. 2 and 3, perithecia in longisection are shown. As seen under the 
hand lens the wall of the body of a perithecium is gray or lead-colored, 
while the neck is jet black and shining like anthracite. The mature 
perithecia measure about 350 to 400 uw in diameter and are mostly spherical, 
but the shape is often modified by pressure of surrounding perithecia. 
Since the perithecia are always in the bottom of the stroma next to the 
host tissue, the length of the neck varies with the luxuriance of the stroma 
and the length of the papilla; but, in general, it is four to six times the 
diameter of the body. The black wall of the neck is composed of densely 
