130 



S YSTEMA TIG B TANY. 



filaments elongate by the fission of the cells ; the proto- 

 plasm divides, a cellulose wall is at the same time secreted, 

 and the two daughter-cells then elongate to the normal 

 length. Sometimes the filaments break up spontaneously, 

 and each part gives rise to a new filament. The sexual 

 reproduction takes place by a process called conjugation 

 (Fig. 243). From each of the cells of two filaments lying 

 parallel to each other, slight protrusions arise (Fig. 243, 

 1), and these grow towards each other until they come iu 



contact and unite 

 (Fig. 243, 2). The 

 partition between 

 them becomes ab- 

 sorbed (Fig. 243, 2) ; 

 in the meantime, the 

 protoplasm in each 

 of the two cells con- 

 tracts, rounds itself, 

 and one mass passes 

 gradually through 

 the channel (Fig. 

 243, 3) over into the other cell, where the two unite and 

 form the zygospore (Fig. 243, sp). The old cell-walls 

 decay, and the zygospore falls to the bottom of the water 

 and remains till the process of germination commences. 

 The latter begins by the bursting of the outer hard 

 wall of the spore, the mass within extends in columnar 

 form, secretes cross-partitions, and elongates to the normal 

 form. 



164. The common Fungi, called Moulds {Mucorini), 



243a 



Fig. 243a. Common Mould, partially diagrammatic ; /:, hyphee ; jr>, sporangium ; 

 rf, young sporangia. 



