35 6 FUNGI 



'growth in addition, giving rise to irregularities of shape. The basin- 

 shaped apotheces of Peziza (Discomycetes) and of the gymnocarpous 

 lichens are the characteristic forms, while with them may be placed 

 the large stromata of Morchella (Dill.) and allied genera, which are 

 club-shaped and in the form of stalked caps. The Hysterinese and 

 the Phacidiaceae, Ascobolus (Pers.), Pyronema (Fckl.), &c., which 

 show no marginal extension, approach the Pyrenomycetes in this 

 respect. 



The perithece does not differ essentially from the apothece. As a 

 rule it is much smaller, rarely more than one millim. in diameter, and it 

 consists of an outer wall enclosing an ascogenous hymenium at all 

 points but one narrow opening, the ostiole. The whole perithece is 

 round or flask-shaped, and the ostiole is simply a pore in the wall or a 

 channel through the neck of the flask. In other words, while an 

 apothece is generally larger, it does not differ in any marked way from 

 a perithece, except that its hymenium has an open surface, while the 

 margin of the perithece is arched over, leaving only a narrow opening 

 for the escape of the spores. The asci arise from ascogenous hyphae, 

 either exclusively at the base of the perithecial cavity or at all points of 

 the inner surface, and in successive crops, producing in all a considerable 

 number of ascospores. The envelope consists of a wall which, when a 

 stroma is absent and the peritheces appear singly on the mycele, is com- 

 posed of a dense pseudo-parenchyme clothed sometimes externally with 

 hairs. Where the peritheces are borne on a stroma there is no sharp 

 differentiation of wall-structure. The neck, when present, is but a pro- 

 longation of the wall, and the ostiole arises (for at first the cavity is fully 

 closed) as an intercellular passage either schizogenously by the separation 

 of tissue through unequal growth, or lysigenously by the absorption of 

 the tract of tissue originally occupying its place. In many cases it is 

 hard to say by which process it arises, and it is likely enough that both 

 sometimes have a share in it. One distinguishes here between para- 

 physes which arise and stand in relation to the asci as in the apothece, 

 and periphyses, by which is meant other hairs of like origin arising from 

 the hymenium at places where there are no asci for example, in the 

 region of the neck. Sometimes the periphyses protrude through the 

 ostiole. They are always present in greater or less numbers, except, 

 according to Fiiisting, in Massaria (De Not.) ; while paraphyses are absent 

 from a number of genera, both of fungi and of lichens. In Chaetomium 

 fimeti (Fckl.) the perithece remains closed, and this transition form leads 

 us to the division which possesses cleistocarps. 



Just as the peritheces are essentially folded over apotheces, so the 

 cleistocarps may be described in general terms as peritheces which 



