26o 



THALLOPHYTES. 



lays the surface of the folded pileus ; in Peziza it clothes the concavity of the cup, 

 which is either flat and sessile (Fig. 182) or stalked. The hymenium consists of 

 paraphyses and asci, in which eight spores are usually formed simultaneously ; the 

 paraphyses generally appear earlier, but are finally crowded out by the asci. The spores 

 sometimes possess nuclei, but are sometimes destitute of them (Fig. 182). The Disco- 

 mycetes agree, however, with the Pyrenomycetes — from which they are principally 

 distinguished by their gymnocarpous receptacles — in the occurrence of spermogonia, 

 pycnidia, and conidia, as forerunners of the ascospores. In Peziza Dur'mana two 

 kinds of receptacles have even been observed, one with larger ascospores, which put 

 out germinating filaments, the other also with ascospores, which, however, form a pro- 

 mycelium from which minute spores are detached. The variety of structure is further 

 increased by the fact that many species produce sclerotia. Peziza Fuckeliana is a 

 peculiarly interesting example. Its sclerotium is developed, according to De Bary, in 



Fig. 181. — Claviceps purpurea ; A a sclerotium forming a receptacle d (ergot) ; B longitudinal section of upper part of a 

 receptacle, cp the perithecia ; C a perithecium with the surrounding tissue (greatly magnified) ; cp its orifice, hy hyphae of the 

 pileus, sh epidermal layer of the pileus ; D an ascus ruptured and allowing the spores to escape (after Tulasne). 



the tissue of decaying vine-leaves in autumn and winter ; if it is placed when fresh, or 

 after having been for some time at rest in the dry, upon the surface of damp ground, 

 it begins after about twenty-four hours to put forth conidia-bearing hyphae, and these 

 prove to be identical with Botrytis cinerea. If, on the other hand, the sclerotium is buried 

 beneath the surface of the soil to the depth of i cm., it does not put out conidia- 

 bearing hyphae of this kind, but produces, on the contrary, in the summer following its 

 production, stalked trencher-shaped little cups, the ascus-bearing receptacles. Sclerotia 

 sometimes again arise from the germinating filaments of the ascospores without any pro- 

 duction of conidia. In other cases the mycelium which grows luxuriantly in the vine- 

 leaves puts out Botrytis-threads at the same time that the formation of sclerotia takes 

 place ; from the germinating filaments of the conidia (of the Botrytis) De Bary always 

 saw Botrytis again produced first of all, and its mycelium probably also forms sclerotia. 



Like the perithecia of the Pyrenomycetes, the receptacles of the Discomycetes arise 

 from a peculiar act of sexual union which takes place on the mycelium, so that the 



