GROUP I. THALLOPHYTA : FUNGI : ASCOMYCETES. 



301 



Order II. Pyrenomycetes : asci forming a hymenial layer, with an invest- 

 ment ; the ascocarp is either a cleistothecium or a perithecium ; a stroma is 

 present in some families. 



The ascocarp is a cleistothecium in the sub-order Perisporiaceae, including 

 the families Erysipheaa (the Mildews) and Perisporiese (e.g. Eurotium and 

 Penicillium) ; in these families there is no stroma. 



In this order the Tuberaceae, Truffles, may be included (e.g. Tuber cestivum, 



FIG. 211. ISurotium, repens. A A portion of the mycelium with a simple gonidiophore 

 (c) bearing gonidia ; the gonidia have already fallen off from the sterigmata (st) ; as, a 

 young ascogonium. B Ascogonium (as) with a pollinodium (p). C Another, with hyphae 

 growing up round it. I) A cleistothecium seen on the exterior. E F Sections of unripe 

 cleistothecia ; w the investment; / ascogenous hyphse arising from the ascogonium, 

 which subseqently bear the asci. G An ascus. H A ripe ascospore. (Magnified : after 

 Sachs.) 



brumale, etc., Elaplwmyces granulatus) ; the only reproductive organs which they 

 are known to possess are the large cleistothecia which have a complex structure. 

 The ascocarp is a perithecium in the sub-orders Hypocreaceaa (e.g. Polystigma, 

 Melanospora, Nectria, Epichloe, Claviceps, Cordyceps), Sphaeriaceas (e.g. Chaeto- 

 mium, Sordaria, Xylaria, Hypoxylon, Pleospora, Spbserella), and Dothideaceae : 

 a stroma, which varies much in form, is frequently present. 



