294 PART IV. CLASSIFICATION. 



the paraplujses, which are situate in the hymenial layer between 

 the asci. 



The following forms of ascocarp may be distinguished amongst 

 those which have a cellular investment : the cleistothecium ; the 

 investment remains closed until it decays and ruptures to permit 

 of the escape of the ascospores (see Figs. 173, 175): ihe> pcrithe- 

 cium; a narrow aperture is developed opposite to the hymenial 

 layer (see Fig. 176) : the apothecium ; the investment is somewhat 

 saucer-shaped, so that the hymenial layer is fully exposed (see 

 Fig. 177). 



The ascus is in all cases unicellular. It may be either spherical 

 (e.g. Eremascus, Eurotium), or oval, or club-shaped (e.g. Peziza) in 

 form. In some cases the ascospores are ejected with considerable 

 force ; in others they are set free on the mucilaginous degeneration 

 of the wall of the ascus. 



The ascopores are formed by free 

 cell-formation (see Fig. 64, p. 86) 

 from a portion only of the proto- 

 plasmic contents of the ascus, pre- 

 ceded by nuclear division. The 

 unused portion of the protoplasm 

 is termed the cpiplasm, and is rich 

 in a carbohydrate called glycogen. 

 In nearly all cases eight ascospores 



Fro. 173. A Ascocarp of UnetrmZa It- , , 



oroi. (Erysipheie), slightly magnified: are formed ; m some cases each of 



m mycelium; / cleistothecium; ft, in- the eight Spore-rudiments under- 

 vesting filaments. B An ascus from tho -,? . . , , 

 cleistothecium. containing eight asco- & oes dlvision to form a compound 

 snores (more highly magnified). Spore (e.g. Hysterium, Pleospora, 



etc.), the cells of which may either 



separate or remain coherent. The form of the ascospore is spherical, 

 or oval, or rarely filamentous (e.g. Claviceps, Fig. 176). The wall 

 generally consists of exospore and endospore: the protoplasm 

 generally contains oil-drops. 



The germinating ascospore usually gives rise directly to the 

 ordinary mycelium. 



The Ascomycetes may be classified as follows: 



Order L Gymnoasceae : asci withqut any investment, or with only a 

 rudimentary investment, either solitary, or forming a hymenial layer. 



The typical members of this group are Eremascus (Fig. 171), Gymnoas- 

 cus, and Exoascus parasitic on various trees. 



It is now customary to place in this order the family of the SACCHA- 



