356 



BOTANY 



water absorbed, and discharges its spores through the opening, or the spores are set 

 free within the peritheoia, and are ejected, embedded in a swollen mass of slime. 



The simplest Pyrenomycetes possess free 

 peritheeia growing singly on the incon- 

 spicuous mycelium, having the appearance 

 of small black dots irregularly disposed over 

 the surface of the organic substratum. In 

 other cases the formation of the fructifica- 

 tions is more complicated ; they arise in 

 groups embedded in a cushion- or club-shaped, 

 sometimes branching, mass of compact 

 mycelial hyphte having a dense pseudo- 

 parenchymatous structure. Such a fructifica- 

 tion is known as a stroma. 



In the life-history of most Pyrenomycetes 

 the formation of peritheeia is preceded by 

 the production of various accessory fructi- 

 fications, particularly of conidia, which are 

 abstricted in different ways, either directly 

 from the hyphse or from special conidio- 

 phores, and are especially efficacious in dis- 

 seminating the Fungi. The conidiophores 

 are frequently united in a conidial stroma in 

 the form of incrustations or wart- or club- 

 shaped mycelial masses ; they then consti- 



FiG.ars.-PeritheciumofPodosporoySmiMte t t distinct coniclial fructifications: A 

 in longitudinal section, s, Asci ; a, ' . . 



paraphyses ; e, periphyses ; m, mycelial special form of such eomdia-fruits are the 

 liyphse. (After v. Tavel, x 90.) PYCNIDIA produced by many genera. They 



are small spherical or flask-shaped bodies 



which in structure resemble the ascogenous peritheeia, but, instead of asci, they 



give rise to branched hyphal filaments from the apices of which conidia, in this 



case termed pyonospores or pycxo- _., 



coxidia, are abstricted (Fig. 279, 1, 



2). The different kinds of fructifica- 

 tions in the Pyrenomycetes usually 



make their appearance in succession. 

 As representatives of the Pijrenu- 



mycetes with free peritheeia may be 



cited the numerous species of the 



genus Spliaeria, which appear as jet 



black, spherical bodies upon dry stems 



and leaves. An example of a species 



forming a stroma is afforded by Nectria 



cinnabarina. This Fungus occurs on 



the dried branches of deciduous trees 



and produces small, nearly round or 



somewhat elongated stromata of a 



cinnamon -red colour. At first the 



stromata give rise only to filamentous 



conidiophores from which conidia are abstricted, but they afterwards develop sunken 



peritheeia. Xylaria hypoxylon, common on rotten tree-stumps, produces an erect, 



Fig. 279. — 1, Conidiophore abstricting conidia, 

 from a pyemdium of Cryptospora liypodermia. 

 (After Brefeld, x 300.) 2, Pycnidium of Stric- 

 keria obdiictms in vertical section. (After 



TuLASNE, X 70.) 



