ENDOTHIA PAEASITICA AND RELATED SPECIES. 27 



the pycnidial cavity is sometimes small and simple, as described by 

 Ruhland, it is more often large and much convoluted. (See Pis. 

 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 stroma ta. 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 E. parasitica 

 examined average somewhat larger than those of E. fuens, the range 

 of the pycnidial stromata is about the same in the two species, vary- 

 ing from 0.-1 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 E. 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 E. parasitica and of E. fluens^ 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 E. 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 to 3 mm. in width. The stromata of E. singularis 

 are much larger than those of any other species of Endothia, being 



