28 BULLETIN" 380, U. S. DEPARTMENT OF AGRICULTURE. 



usually from 2 to L mm. in length and 3 to 5 mm. or more in diameter. 

 They are decidedly erumpent, rather regular, and subgiobose in out- 

 line. The contents of the stromata are brick red in color and are very 

 powdery when old. 



The stromata of Endothia fiuens, E. fiuens mississippiensis, and 

 E. parasitica resemble each other so closely that the species are prac- 

 tically indistinguishable on this basis. All these species are char- 

 acterized by partially embedded, confluent stromata which vary 

 greatly in outline, depending on the nature of the bark of the host. 

 As already stated, they vary from 0.4 to 2 mm. in height and from 

 0.7 to 5 mm. or more in length where confluent. E. tropicalis and 

 E. longirostris resemble this group in their stromatic characters. 



Pycnidia. — The pycnidia of Endothia gyrosa and E. singularis are 

 very distinctive also. The pycnidial cavities of E. gyrosa are narrow 

 and so irregularly convoluted that in a section of the stroma the 

 cavities vary in width from 0.03 to 0.3 mm., averaging about 0.15 

 mm. On the whole, however, they are much narrower than those 

 of E. -fiuens or E. parasitica. A section of a pycnidial stroma of E. 

 gyrosa shows numerous irregular, rounded to elongate chambers 

 separated by narrow walls. The pycnidial cavities of E. singularis 

 (PI. XIII) are minute, 0.03 mm. in diameter, nearly spherical, 

 evenly distributed through the stroma and separated at first by com- 

 paratively thick walls, which disintegrate and become powdery when 

 the stroma is old. 



So far as the writers have been able to determine, the " tendrils " 

 of pycnospores so characteristic of Endothia fiuens and E. parasitica 

 are not formed in either E. gyrosa or E. singularis. Mature pycnidial 

 stromata of E. gyrosa when placed in a moist chamber exude nu- 

 merous droplets containing spores and scattered well over the surface 

 of the stromata. The writers have been unable to produce any such 

 change by placing the pycnidial stromata of E. singularis in moist 

 chambers, and it seems probable that the pycnospores of E. singularis 

 are set free by the breaking down of the outer walls of the stromata. 

 As already mentioned, the inner partitions are friable, so the spores 

 are readily scattered by the wind. 



The pycnidial cavities of Endothia fiuens and E. parasitica, and 

 apparently all the other species of this section of the genus, vary 

 from 0.2 to 0.3 mm. or more in diameter and may consist of a 

 single chamber rather regular in outline (PI. XIY, fig. 1) or of an 

 irregular cavity consisting of many chambers (PL XY, fig. 3) more 

 or less completely separated from one another. These species differ 

 from E. gyrosa in that the pycnospores are usually discharged through 

 a single opening near the top of the stroma and emerge in a single 

 twisted tendril. 



