v] HYPOCREALES 143 



HYPOCREALES 



The Hypocreales are readily distinguished by the clear colour and more 

 or less fleshy consistency of the perithecium or stroma. In the majority of 

 Pyrenomycetes the colour is black or dark brown, but here bright red, 

 yellow, blue, and various paler shades are found, and it is only quite 

 occasionally that so dark a tint as brown or dirty violet appears. 



The asci contain usually eight, sometimes four, and sometimes many 

 spores. The spores are in most cases hyaline, but are dark-coloured in 

 Melanospora and its allies ; they are elliptical or filiform, and may be one 

 or more celled. 



In a number of species conidia as well as ascospores are produced. 



The group includes both saprophytic and parasitic forms. 



There are some sixty genera of Hypocreales, and the group is subdivided 

 primarily according to the development of the stroma. In the simplest forms 

 the stroma is absent, and the separate perithecia may or may not be partly 

 sunk in the substratum, in others a filamentous or a fleshy stroma appears, 

 and the perithecia are more or less embedded. In the highest members the 

 perithecia originate deep in the stroma, and remain immersed in it throughout 

 their development. 



Upon these characters the subdivision of the group is based : 



Stroma absent, or, when present, with perithecia entirely 



superficial NECTRIACEAE. 



Stroma forming a conspicuous matrix in which the peri- 

 thecia are partially or entirely immersed HYPOCREACEAE. 



Nectriaceae 



The species of the genus Hypomyces are for the most part parasitic upon 

 the pilei of various Hymenomycetes. H. aurantius occurs on old Polypori 

 and on species of Stereum. 



Here the free perithecia are roughly oval in form, orange yellow in 

 colour, and seated on a delicate filamentous stroma. The perithecium wall 

 consists of an outer coat of narrow, closely woven hyphae, and an inner 

 layer of larger, thinner-walled cells with scanty contents. The cavity becomes 

 filled with paraphyses and developing asci, and is prolonged into the neck 

 lined with short periphyses. The spores are two-celled and the wall at each 

 end is usually prolonged into a point. 



Development has been studied by Moreau in Hypomyces lateritus, a form 

 parasitic on species of Lacterius, and placed by Maire in the genus Peckiella 

 by reason of its unicellular spores. The cells of the vegetative mycelium are 

 uninucleate, and the archicarp appears among them as a coil of uninucleate 



