THALLOPHYTA— FUNGI 



85 



Fig. 842. 



called parapliyses. Each ascus develops eight spores from part 

 of its protoplasm, the rest remaining as epiplasm. 



In some species the fructification is in the form of a deep or 

 shallow cup, sometimes nearly closed. This is called a perithe- 

 cium {fig- 841). 



The group of the Saccharomycetes is now generally referred to 

 this sub- class. These plants are represented by the Yeasts^ which 

 have the power of setting up alcoholic fermentation in sugary 

 fluids. They are simple cells of rounded or ovoid form which 

 multiply with great rapidity by a 

 process of budding. "When growing 

 rapidly, sometimes chains of cells are 

 formed, owing to the budding taking 

 place before separation of the cells. 

 Under certain conditions, usually 

 when badly nourished, the yeast cell 

 forms four spores by free cell-forma- 

 tion in its Ulterior. There is, how- 

 ever, no sexual apparatus ever pro- 

 duced. Each such cell may be looked 

 upon as an ascus and the four spores 

 as ascospores. 



Besides these so-called sexual pro- 

 cesses, most of these fungi can pro- 

 duce gonidia in great numbers. 

 They are borne upon erect aerial 

 hyphae by a process of abstriction 

 from their termmal cells called 

 sterigmata {fig. 842). Each ste- 

 rigma can thus produce a chain of 

 gonidia. Sometimes the aerial 

 hypha or gonidiophore terminates in /'?v/.842.stjiogonidiaofEurotium, 

 a single sterigma, sometimes _ it HS^^t,:!' ^''''''''''''' ''''''^ 

 branches near the apex, forming 



several. Sometimes the gonidiophores are found in numbers in 

 special receptacles called, injcnidia. 



We have thus an alternation of generations in most members 

 of the group, the ordinary mycelium being the gametophyte, and 

 the ascocarp the sporophyte. Homologous alternation almost 

 always occurs, many gametophytes in succession bearing only 

 gonidia, till one appears which produces the sexual organs. In 

 a few genera, however, no gonidia are foiuid. 



A curious case of homologous alternation occurs in some 



