5 o TEXT-BOOK OF FUNGI 



vertical septa formed at right angles. Each of the four 

 cells grows upwards into a long, stout sterigma. 



In the Ascomycetes the ascus or spore mother-cell varies 

 much in size and form in different groups. It is usually 

 comparatively large, and varies from almost globose or 

 broadly piriform in the Erysipheae, to narrowly cylindrical 

 and elongated in many of the Discomycetes. Where the 

 sporophore is more or less cup-shaped, with an exposed 

 flat hymenium, as in species of Peziza, the asci are packed 

 side by side like basidia, and are intermixed with slender 

 paraphyses, and the often brilliantly coloured disc or 

 hymenium is due to coloured pigment present in the 

 swollen tips of the paraphyses. 



The hyphae bearing the asci ascogenous hyphae origi- 

 nate from the oogonium or female sexual organ after fer- 

 tilisation, whereas the paraphyses are a continuation of the 

 vegetative hyphae. 



The protective portion or fruit enclosing the asci is also 

 of vegetative origin, and usually originates as outgrowths 

 from one or more cells situated immediately below the 

 oogonium. The fruit varies much in form and texture. 

 In many of the Sphaeriaceae it takes the form of a sphere, 

 or is more frequently flask-shaped, with a more or less pro- 

 nounced neck through which the spores escape when 

 mature. A structure of this kind is called a perithecium. 

 The perithecium may have no external opening, and 

 consequently has to decay or rupture irregularly before 

 the spores are liberated, as in the Perisporieae ; or it is 

 furnished with a definitely formed opening or ostiolum, 

 through which the spores escape as in Sphaeriaceae. 



When the hymenium is enclosed in a perithecium or 

 other structure, as in Eurotium, Sphaeria^ and the puff-balls, 



