mv. i THALLOPHYTA 445 



Order 4. Discomycetes C 89 ) 



The Discomycetes are distinguished from the other orders by their open apothecia, 

 which bear the hymenium, consisting of asci and paraphyses, freely exposed on 

 their upper surface (Figs. 381, 389). The different groups exhibit great diversity 

 as regards the manner of development of their fructifications. 



The great majority of the Discomycetes, of which the genus Peziza may serve 

 as a type, grow on living or dead vegetable substances, especially upon decaying 

 wood, but sometimes also on humus soil. They produce saucer- or cup-shaped 

 fructifications of a fleshy or leathery consistency, and usually of small dimensions. 

 One of the largest forms, Peziza aurantiaca (Fig. 388), has irregularly bowl-shaped 

 fructifications, which may be seven centimetres broad and of a bright orange-red 

 colour, while in most of the other species they ar.e grey or brown. Such cup- 

 shaped fructifications are termed APOTHECIA. 



FIG. 388. Peziza aurantiaca. 

 (Nat. size. After KROMBHOLZ.) 



FIG. 389. Lachnea pulcherrima. Apothecium ruptured, 

 showing old and young asci between the paraphyses. 

 (After WORONIN, from v. TAVEL.) 



The development of the apothecium may be described for Pyronema confluens, 

 in which it was first thoroughly investigated by R. HARPER. The fruit-body of 

 this species is about 1 mm. across, and of a yellow or reddish colour ; it often 

 occurs on spots where fires have been kindled in woods. The carpogonia are 

 especially large in this species, and several usually take part in the formation of 

 each apothecium (Fig. 390 A). The carpogonium or ascogonium consists of the 

 spherical, multinucleate oogonium, on the apex of which a multinucleate curved 

 cell, the trichogyne, is situated. The cylindrical, multinucleate antheridium 

 arises from a neighbouring hypha ; its apex comes into open communication with 

 the tip of the trichogyne by the breaking down of the intervening walls. The 

 male nuclei first wander into the trichogyne cell, and then, by the breaking down 

 of the basal wall of the latter, into the oogonium. The egg-cell then becomes 

 limited from the trichogyne by a new cell wall and sends out ascogenous filaments 

 containing the conjugate nuclei. These filaments branch and ultimately ter- 

 minate in asci (E), while the sterile hyphae and the paraphyses of the fructifica- 

 tion are derived from hyphae arising beneath the carpogonium. According to 

 HARPER. the male and female nuclei fuse in pairs with one another in the 

 carpogonium. More recent investigations by CLAUSSEN show that they only place 



