184 ASCOMYCETES. 



a rule they reach maturity only on the dead remains of host 

 plants. Many of them are enemies of woody plants, and the 

 mycelium of some can live in the elements of the wood itself, 

 hence they constitute a dangerous group of wound parasites. 

 The Pyrenomycetes may be sub-divided thus : 



1. The Hypocreaceae having soft coloured perithecia often 

 placed several together on a stroma. 



2. The Sphaeriaceae with firm dark-coloured perithecia 

 frequently embedded in a stroma. 



3. The Dothideaceae with perithecia so embedded in a 

 stroma that they have no distinct wall of their own. 



All three divisions include forms parasitic on plants. 



(1) HYPOCREACEAE. 



The Hypocreaceae consists of a single family bearing the 

 same name. Of the seventeen genera contained therein only 

 six contain plant parasites, viz. : — Gibberella, Ccdonectria, Nectria 

 (including Nectriella), Polystigma, JEpichlo'e, Claviceps. The re- 

 mainder are saprophytic only, and do not come within the 

 scope of the present work : they are — Melanospora, Selinia, 

 Meutheromyces, Hypomyces, Sphaerosiilbe, Letciidraea, Hypocrea, 

 Pleonectria, Barya, Oomyces, and Gordyceps. 



Gibberella. 



The perithecia have a transparent blue or violet colour, and 

 form tufts on the stromata. A stroma is not present in all 

 the species. The spores are light-coloured, and spindle-shaped 

 ■or oblong. 



6. moricola Ces et de Not. Passerini gives this as the cause 

 of a disease of young twigs of mulberry. 



G. pulicaris (Fr.) is very frequently found on trees. (Britain). 



Galonectria. 



The perithecia are yellow or red, and occur isolated or several 

 together. The asci contain spores composed of three or more 

 cells, rarely of one cell. 



0. pychroa Desm. causes death to young leaves of planes 

 (esp. P. occidentalis) ; it also multiplies by means of conidia 

 {Fvsarium platani). 



