STRUCTURE. 61 
least when dry. In some species of Hysteriwm, the sporidia are 
remarkably fine. M. Duby* has subjected this group to ex- 
amination, and M. Tulasne partly so.f 
Sru#riacel.—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. ; Fic. 35.—Perithecium of Spheria 
As in the Discomycetes, the hyme- een 
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 JLucedines and Dema- 
tiet, especially in the genus Helminthosporium, bear the conidia 
of species of Spheria, so that this may be regarded as one form 
of fruit. 
Perithecia, very similar externally to those of Spheria, but 
containing spores borne on slender pedicels and not enclosed in 
asci, have had their relations to certain species of Spheria indi- 
* Duby, ‘‘ Mémoire sur la Tribu des Hysterinées,” 1861. 
+ Tulasne, ‘‘ Selecta Fungorum Carpologia,” vol. iii. 
