126 



BOTANY. 



pastry, etc. (Mucor mucedo), is as follows: The vertical 

 hyphse, which are filled with protoplasm, become enlarged 

 at the top, and in each a transverse partition forms {A, a, 

 Fig. 58), the portion above the partition {b) becomes larger, 

 and, at the same time, the transverse partition arches up 

 {B, a), finally appearing like an extension of the hypha, 

 then called the columella {G, a). The protoplasm in the 

 enlarged terminal cell (S) divides into a large number of 

 minute masses, each of which surrounds itself with a cell- 



A 



■a 



Fig. 58.— Diagrams shomngmode of growth of the spore-case of Mucor mu- 

 cedo. A, very young stage;^, somewhat later; C, spore-case with ripe spores. 

 a in all the figures represents the partition- wall hetween the last cell of the fila- 

 ment and the spore-case, b. 



wall; these little cells are the spores, and the large mother- 

 cell is now a spore-case, or sporangium. 



266. The spores are set free in difPerent ways: in some 

 cases the wall of the spore-case is entirely absorbed by the 

 time the spores are mature; in other cases only portions of 

 the wall are absorbed, producing fissures of various kinds. 

 The spores germinate readily when on or in a substance 

 capable of nourishing them, by sending out one or two 

 hyphse, which soon branch and give rise to a mycelium. 

 Spores may, if kept dry, retain their vitality for months. 



267. Sexual reproduction takes place after the produc- 

 tion of asexual spores. Two hyphse, in the air or within 



