268 GENERAL MORPHOLOGY OF PLANTS 



or completely buried in the ground, the dormant mycelium in 

 the " mummies " develops the cups, which are supported on 

 long stalks to lift them above the ground. 



Fig. 232. 



Sclerotina fructigena, the trumpet-shaped fruit bodies growing from old peach mummies 

 which were affected with the rot. Natural size. 



430. The morels. These are large fleshy fungi with a stout 

 stalk bearing a large head which is covered with numerous shallow 

 depressions separated by ridges. The entire surface of the head 

 is covered with the asci intermingled with numerous sterile 

 hyphae (paraphyses). The morels (Morchella) appear in damp 

 places in early spring and are prized as edible fungi. They are 



sometimes called mushrooms, but do not belong to the true 

 mushroom group. 



431. The yeast fungi. The yeast fungi, or sprouting fungi, as 

 they are often called, are by some classed among the sac fungi as 

 degenerate forms. The yeast plant is remarkable for its activity 

 in producing fermentation especially of solutions containing sugar 

 (see paragraph 192 for fermentation by yeast), giving off CO 2 and 

 forming, alcohol; one yeast (Saccharomyces cerivisece) is used 

 both in bread-rising and in brewing beer. The yeasts usually 

 consist of single cells, oval or elliptical in form, and in this con- 

 dition they are single-celled plants. They multiply by a process 

 of budding or sprouting. Near each end of a cell a small bud 

 appears which has only a frail connection with the parent yeast cell. 

 This bud increases in size, and soon separates, forming a new yeast 

 plant. Sometimes these buds remain connected for a time, form- 

 ing small colonies, which soon separate into the separate cells if 



