STRUCTURE. Gl 



least when dry. In some species of Hysterium, the spOridia are 

 remarkably fine. M. Duby* has subjected this group to ex- 

 amination, and M. Tulasne partly so.f 



SPH^RIACEI. In this group there is considerable variation, 

 within certain limits. It contains an immense number of 

 species, and these are daily being augmented. The general 

 feature in all is the presence of a perithecium, which contains 

 and encloses the hymenium, and at length opening by a pore 

 or ostiolum at the apex. In some the perithecia are simple, in 

 others compound ; in some immersed in a stroma, in others 

 free ; in some fleshy or waxy, in others carbonaceous, and in 

 others membranaceous. But in all there is this important dif- 

 ference from the Ascomycetes we have already had under con- 

 sideration, that the hymenium is never exposed. The perithe- 

 cium consists usually of an external 

 layer of cellular structure, which is 

 either smooth or hairy, usually black- 

 ish, and an internal stratum of less 

 compact cells, which give rise to the 



hymenium. FlG 3 5.-Perithecium of Sphceria 



As in the Discomycetes, the hyme- 

 nium consists of asci, paraphyses, and mucilage, but the whole 

 forms a less compact and more gelatinous mass within the peri- 

 thecium. The formation and growth of the asci and sporidia 

 differ little from what we have described, and when mature the 

 asci dehisce, and the sporidia alone are ejected from the ostiolum. 

 We are not aware that operculate asci have yet been detected. 

 It has been shown in some instances, and suspected in others, 

 that certain moulds, formerly classed with Mucedines and Dema- 

 tiei, especially in the genus Helminthosporium, bear the conidia 

 of species of Sph&ria, so that this may be regarded as one form 

 of fruit, 



Perithecia, very similar externally to those of Sphceria, but 

 containing spores borne on slender pedicels and not enclosed in 

 asci, have had their relations to certain species of Spharia indi- 



* Duby, ^M^moire sur la Tribu des Hysterinees," 1861. 

 t Tijlasne, '< Selecta Fungorura Carpologia," vol. iii. 

 4 



