SPHAERIALES 281 



mycelium often develops in the surface layers of bark cells just beneath 

 the ectostroma, and fuses with it, giving the appearance of an ectostroma 

 partially sunken in the bark. Such a fusion and consequent extension of 

 conidial locules into the entostromatic portion of this tissue, is charac- 

 teristic of this series. 



In Diatrypella quercina, the greenish yellow ectostroma develops 

 above the perithecia. In D. Frosiii the isolated entostromatic areas 

 ordinarily contain a single group of perithecia. Diatrypella betulina 

 represents the highest stage of the series. The widely erumpent blackish 

 disc contains separately erumpent, quadrisulcate, disc-like ostioles. The 

 disc tissue consists entirely of yellowish green fungus tissue with a black- 

 ened surface crust. It originates upon the bark surface beneath the 

 periderm and is ectostromatic. The ectostroma is not deciduous but 

 forms the erumpent disc itself. The perithecia arise within a hyaline 

 entostroma, increase enormously in diameter and push up the ectostroma. 



The third series stage is found in Eutypella and is characterized by the 

 8-spored asci, the small but distinct ectostroma with the conidial locules 

 formed in the entostromatic tissue of the bark. The species vary from 

 those with an effused entostroma to those with definitely isolated stro- 

 mata. Eutypella tumida shows this whole range of variation in a single 

 species. 



In the fourth series, which is more heterogeneous, the stromatic develop- 

 ment occurs mostly in the entostroma with a great reduction of the 

 ectostroma. The spores have a tendency to become dark brown, straight 

 cylindrical and uniseriate ; the asci become cylindrical and shorter stalked, 

 with an increase in the filiform hyaline paraphyses. Species of Cryplo- 

 sphaeria, Valsaria and Anthostoma illustrate these tendencies. 



Diaporthaceae. — In this family the asci have no definite stalks and 

 do not remain in a definite hymenial layer after maturity. When mois- 

 tened, the base of the ascus contracts and dissolves, pinching off the ascus 

 from its attachment. The ascus walls are delicate and break down in 

 water. As a result, the entire central cavity of the perithecium becomes 

 filled with a mass of free asci and spores. The paraphyses which are 

 numerous in young perithecia are evanescent. In the higher forms they 

 are more numerous and persistent in mature perithecia. Most species 

 have two types of conidia. 



The first series includes Diaporthe, Melanconis and Pseudovalsa. There 

 is a general tendency toward the development of a stroma and the cluster- 

 ing of perithecia. In Diaporthe the spores remain hyaline, in Melanconis 

 they become brown in the higher forms, in Pseudovalsa they become brown 

 and multicellular. In Diaporthe the conidia are hyaline, unicellular 

 within pycnia; in Melanconis the conidia become brown, unicellular, and 

 the conidial layers more exposed ; in Pseudovalsa they become brown and 

 septate. 



