ENDOTHIA PARASITICA AND RELATED SPECIES. 27 
the, pycnidial cavity is sometimes small and simple, as described by 
Ruhbland, it is more often large and much convoluted. (See Pls. 
XV and XVI.) 
While the writers, of course, agree with Pantanelli (60) that 
Endothia parasitica and E. fluens are distinct species, many of the 
stromatic characters which he describes are so variable as to be 
unreliable. In an examination of a large number of specimens the 
writers have been unable to find any constant difference in the ar- 
rangement or structure of -the pycnidial stromata. This seems to 
depend chiefly in both species on the character of the bark and the 
moisture conditions. As to size, while the stromata of Z. parasitica 
examined average somewhat larger than those of Z. fluens, the range 
of the pycnidial stromata is about the same in the two species, vary- 
ing from 0.4 to 2 mm. in height and from 0.2 to 3 mm. in length. 
The ascogenous stromata are also very variable in size. Those 
measured by the writers varied in height from 0.5 to 2 mm. in En- 
dothia parasitica and from 0.5 to 2.3 mm. in £. fluens. In width the 
perithecial stromata were from 1 to 2.5 mm. in both species, while 
there is apparently no method for determining their length, since on 
thick-barked trees continuous narrow masses of perithecial stromata 
are often formed in the crevices of the bark. These stromatal masses 
frequently extend from 5 to 10 cm., and while they are in all prob- 
ability formed by the fusion of several stromata there is no way of 
determining how far each extends. 
The arrangement of the perithecia mentioned by Pantanelli (60) 
as a specific character seems to depend on the nature of the bark of 
the host. When the bark is thin and easily ruptured the stromata 
tend to spread out so that the perithecia occur in a single layer, 
while if the bark is thick and deeply ridged the stromata are thicker 
and the perithecia occur in two or more layers. That this is not a 
specific character is clearly shown by Plate XVI. Figures 1 and 3 
of this plate show a stroma of £. parasitica and of F’. flwens, respec- 
tively, both with three layers of perithecia, while Plate XVI, figure 2, 
and Plate X, figure 1, show stromata of both species with perithecia 
arranged in a single layer. 
Although, as already indicated, the stromata of each species are 
very variable, they are sufficiently distinct so that the native American 
species may readily be distinguished in the field. 
The stromatic characters of Endothia gyrosa and E. singularis 
are much more distinct than those of the other species. The stromata 
‘of EZ. gyrosa are erumpent, irregularly subglobose, with a rather 
roughened surface. They are usually from 1.5 to 2 mm. in height 
and vary from 1.5 to3 mm. in width. The stromata of £. singularis 
are much larger than those of any other species of Endothia, being 
