2 --6 THA LL OPIIYTES. 



and branched. The section of a truffle shows a dark matrix (the fertile tissue), in 

 which run two kinds of branching veins ; — the one opaque and destitute of air, com- 

 posed of the main branches of the fertile hyphae, spring from the inner surface of the 

 peridium ; the other white and air-conducting are prolonged to its outer surface. Hyphae 

 of the adjacent tissue begin to grow into these last-mentioned cavities from an early 

 period, and have a white appearance in consequence of the presence of air filling up 

 the spaces between them. The peridium of truffles is a strong shell consisting of 

 pseudo-parenchyma, the outermost cell-walls of which are usually of a brown or black 

 colour. The Asci of the Tuberaceae are globular ; and the spores, furnished with spines 

 or honeycomb-like projections of the exospore, arise in indefinite numbers during a 

 considerable period, and are without nuclei. The formation of spores shows some 

 peculiarities, \Ahich are described by De Bary {I.e. p. io6; cf. also Tulasne, Fungi 

 Hypogaei)\ 



(3) The Pyrenomyeetes^ usually produce in their asci, which are mostly long 

 ' and club-shaped, eight spores formed simultaneously ; they are not unfrequently septate. 

 The asci are formed in the interior of small flask-shaped or roundish receptacles, 

 which are here termed Perithecia. The contents of the perithecium are at first a deli- 

 cate transparent tissue containing no air, which afterwards becomes compressed by, 

 the asci and paraphyses. These spring from a hymenium which clothes the wall 

 of the perithecium or includes only its basal portion. The perithecia are either open 

 from the first (in Sphoeria typhina), or they are at first closed and afterwards form an 

 orifice clothed with hairs, through which the spores escape (as in Xylaria) ; or finally 

 the perithecium is ruptured to admit of their dissemination {e.g. Erysiphe). In one 

 series of forms (Sphaeriae simplices, Pleospora, Sordaria, &c.) the perithecia originate 

 singly or in groups from the filamentous inconspicuous mycelium ; in» others (as Clavi- 

 ceps), a so-called Stroma is first formed, /. e. a pillow-shaped, cap-shaped, arborescent, 

 or cup-shaped receptacle, in which the perithecia usually arise in large numbers 

 (Fig. 811). Besides the ascospores in the perithecia, other forms of spores are also pro- 

 duced by separation from the ends of filaments ; 'vi^.. (i) Conidia (also septate) on 

 filiform receptacles which spring from the mycelium or the stroma (Fig. 180, c) \ 

 (2) Stylospores, essentially like the conidia (simple or septate), formed in the interior 

 of conceptacles which are termed Pycnidia ; and (3) Spermatia, formed in masses in 

 depressed receptacles (Spermogonia), usually very small, often bacilliform or bent, appa- 

 rently not capable of germination, and similar in their origin to the conidia and stylo- 

 spores. The diff'erent forms of spores do not usually appear at the same time either 

 on the same mycelium or the same receptacle ; generally first conidia, then spermogonia, 

 then pycnidia, finally perithecia, although each member of the series (except the peri- 

 thecia) may be absent. 



According to the most recent investigations of De Bary, Woronin, and Fuisting, it 

 is probable that the perithecia of the Pyrenomycetes are always the result of a develop- 

 ment caused by a peculiar sexual union not unlike that of the Florideae. At present 

 this has only been observed with certainty by De Bary in the genera Eurotium and 

 Erysiphe ; but in other genera very dissimilar in other respects to these, tnz. in Sordaria 

 and in Sphoeria Lemannea, Woronin found similar processes of development on the 



^ [Onygenacese are developed on animal substances, as feathers, horns, hoofs, hair, &c. The 

 form of the general receptacle is that of a small round-headed nail. Externally it is smooth and 

 the peridium is brittle, filled with branched threads producing asci at different points, which are 

 soon absorbed, setting free the sporidia. See Berkeley, Outlines of Cryptogamic Bot. p. 272; 

 Tulasne, Ann. des Sci. Nat. 1844, vol. I. — Ed.] 



2 Tulasne, Selecta Fungorum Carpologia. Paris 1860-65. — Woronin and De Bary, Beitriige zur 

 Morph. u. Phys. der Pilze, 3rd series (on Sordaria, Eurotium, Erysij^he, «S<:c.). Frankfort 1S70. 

 — Fuisting, Bot. Zeitg. 1868, p. 179. 



