THE FUNGI 



259 



This differentiation of the plant body of a mold into an aerial 

 and a submerged portion has an important physiological bearing 

 on the life of the plant. The aerial hyphse give rise to the spores, 

 which are thus in a position to be readily disseminated in the 

 air, while the submerged hyphse ramify through the nutrient 



FIG. 139. The habit of the black mold (Rhizopus) growing on bread 



The black heads are the sporangia growing from the aerial mycelium 

 of the mold. After Conn 



medium on which the mold is growing, and both digest and 

 absorb food for the entire fungus plant. The submerged hyphse 

 thus serve the double function of digesting and absorbing foods. 

 We see, therefore, that even in these very simple plants there 

 is a division of labor which amply meets their demands for food 

 and the need for wide distribution. These facts will become 

 clearer by the study of two or three common types of molds 

 selected from two different groups of fungi. The black molds, 

 represented by Rhizopus, belong to the lowest group of algal 



