SPHAERIALES 199 



e. Perithecia at maturity completely emergent from stroma 



Cucurbitariaceae 

 e. Basal portions of perithecia persistently immersed in substrate f 

 f. Ostioles circular Amphisphaeriaceae 



f. Ostioles compressed, appearing elongate-elliptical in cross- 

 section Lophiostomataceae 

 a. Perithecia embedded in substratum or in stroma, but with ostiolar 

 neck only protruding g 

 g. Immersed in substratum, but well-defined stromata not formed h 

 h. Perithecia papillate, asci not usually thickened apically 



Mycosphaerellaceae 

 h. Perithecia beaked, asci thickened apically Gnomoniaceae 



g. Immersed in stromata i 



i. Stromata pulvinate, composed of fungus and host elements j 

 ]. Asci short-stalked and ephemeral Diaporthaceae 



j. Asci long-stalked, spores allantoid Allantosphaeriaceae 



i. Stromata pulvinate or erect, composed wholly of fungal ele- 

 ments; spores dark Xylariaceae 



Throughout the order the asci A\'ithin any perithecium are of 

 different ages. In the larger proportion of species the asco- 

 spores are forcibly expelled. In certain of them, such as the 

 Ceratostomataceae and Fimetariaceae, however, the asci are eva- 

 nescent; and the ascospores are extruded in mucoid droplets, or 

 else the asci break away and are forced intact toward the ostiolar 

 neck, where they rupture. The asci are elongate-clavate, quite 

 generally with ascospores arranged biseriately, obliquely, and in 

 a single row, or else lacking special arrangement. The number of 

 ascospores is mostly 8, but occasional species, such as Neurospora 

 tetraspemia and Fleurage anserina, have 4, or even 2, as in Gno- 

 vionia dispora. Fleurage zygospora bears 16 spores; P. caenileo- 

 tecta, 128; and some species of Sporormia form 256, 512, or even 

 1024. 



Many genera lack paraphyses; in others they are commonly 

 intermingled with the asci. In many species sterile hyphae, 

 periphyses, occur at the periphery of the hymenial area and may 

 also line the ostiolar orifice. 



Conidial production is of common occurrence among the 

 Sphaeriales. Usually the same type of conidia is produced by all 

 species of a given genus, but some genera, as at present delimited, 

 possess as conidial stages a wide variety of conidial types. Quite 

 commonly, too, among plant pathogens the conidial stage occurs 

 during pathogenesis, and the ascogenous stage during sapro- 

 genesis. 



