Enpotuia CANKER OF CHESTNUT 559 
They are closely crowded together, so that in cross section they appear 
to make up a pseudoparenchymatous tissue. These cells are more densely 
filled with protoplasm, and contain more pigment, than the interior cells. 
Pycnidia 
On smooth-bark, young cankers, especially in the summer, the outer 
cork layer is raised in numerous little blisters, with slender, yellow, waxy 
tendrils curling from their ruptured apices (Plate XXXVIII, Fig. 1). 
Under each blister is a single somewhat globose pycnidium, surrounded 
by a scanty, loose growth of white or slightly yellowish mycelium. There 
is as yet no definite stroma. The wall of the pycnidium is composed of 
closely tangled hyphz; that is, it is not a definite pseudoparenchymatous 
wall. The cavity may be a fourth of a millimeter in diameter and is 
almost round in cross section at first, becoming irregular only with age. 
The conidiophores form a dense, brush-like fringe and extend directly 
out into the cavity from every point of the wall (Fig. 86). They are of 
uneven lengths, the majority being 20 to 4ou 
long, and are about 1.5 « in diameter. They may 
be simple or branched. Spores are cut off 
successively from the conidiophores or their 
branches and soon fill the cavity, but, since the 
production of spores does not cease when the 
cavity is filled, they are forced out through an 
irregular ostiole at the top in yellow tendrils. 
These tendrils take on a reddish tinge as they Fic. ler paar of the 
become old. They vary in thickness from the pane ee 
diameter of a hair to half a millimeter, and in  comidiophores, with the 
says a manner of their origin 
length from a millimeter to three or four centi- from the hyphe. Conidi- 
meters. They occur singly and are usually uptareS pore irenches 
spirally twisted into one or more coils (Plate 
XXXVIII, Fig. 1). 
The older pycnidia contained in mature stromata differ from these in 
some respects. The cavity is convoluted or labyrinthiform, and irregular 
(Fig. 84, and Plate XL, Fig. 1). When cross sections of these 
stromata are cut, a single section usually shows a number, of cavities 
which do not appear to be connected; but if the entire stroma is 
cut into serial sections it is found to contain but a single pycnid- 
ium with a number of communicating chambers. Only rarely have the 
writers found stromata containing more than one pycnidium. This 
stage of the fungus has been referred to the genus Cytospora, on the 
erroneous idea of a stroma containing many pycnidia. The cavity of 
the labyrinthiform type of pycnidium often becomes as much as a milli- 
