OEDER SPHAEEIALES 281 



formation of mycelium increases it usually becomes more or less localized 

 about the forming perithecia." Wehmeyer distinguishes between ecto- 

 stroma and entostroma thus: "Ectostroma is that portion of the stroma 

 which is formed on the surface of the bark, beneath or within the peri- 

 derm, and which consists typically of fungous tissue only, except that 

 when it is developed within the periderm it may contain the remnants of 

 the periderm cells, but never of the bark cortex cells. An entostroma is 

 that portion of the stroma which develops within the cortical or woody 

 tissue of the host or substratum and is made up of components of both 

 fungous and host tissues or substratum tissues." Concerning the develop- 

 ment of the entostroma in the progressive specialization of the stroma 

 Wehmeyer remarks: "There is usually correlated, very often beneath a 

 differentiated ectostroma, a clustering of the perithecia." This ento- 

 stroma is often delimited from the surrounding tissues by a thin zone of 

 blackened tissue, forming the black line visible on cutting through the 

 host tissue. Among the variations found in this group of organisms may 

 be noted the following: In a fruiting area (i.e., the region where the 

 perithecia or clusters of perithecia are formed) the perithecia may be 

 scattered or clustered, with or without an entostromatic mycelium about 

 them. If present, according to Wehmeyer, the "entostromatic area may 

 or may not be surrounded by a darkened unorganized zone." It may be 

 lighter in color than the surrounding bark tissue. The ostioles of the 

 perithecia may be separately or collectively erumpent, even clustered 

 perithecia not necessarily being collectively erumpent. A stroma may be 

 effused, i.e., containing numerous separately erumpent perithecia or 

 several clusters of perithecia, or isolated, when it contains only one cluster 

 of perithecia. The portion of the stroma which is erumpent through the 

 periderm or epidermis is the disk. It may be conical or cushion shaped 

 and well distinguished from the entostroma or grading into it. In con- 

 trast to the foregoing are those fungi in which the stroma is compact and 

 composed entirely of fungous tissues and very early becoming external to 

 the substratum. 



The three families of the stromatic Sphaeriales may be distinguished 

 as follows: 



AUantosphaeriaceae : stroma showing all degrees of development described 

 above, but not entirely of fungal structure. Asci with more or less elongated 

 tapering stalks, forming a persistent hymenial layer. Paraphyses mostly 

 evanescent at maturity. Ascospores mostly allantoid, yellowish hyaline, 

 sometimes inequilaterally ellipsoid and brown. Conidia long cylindrical to 

 filiform. 



Diaporthaceae: stroma as in the foregoing family. Asci with short or long 

 evanescent stalks soluble in water so that at maturity the free asci and 

 spores form a loose central mass. Paraphyses present. Ascospores ellipsoid, 

 fusoid, less commonly allantoid, or long cylindrical, hyaline or colored. 



