tive reproduction. The varying conditions under which 

 the plant may be placed of dryness, moisture, light or 

 darkness results in some variation in the process of re- 

 production. 



Asexual Reproduction. 



This takes place by the formation of zoospores, which 

 may be produced in various ways. 



1. If the ordinary vegetative plant be brought into 



water, its protoplasmic contents divide up into 

 numerous zoospores, each containing one or two 

 chromatophores and a nucleus. These escape 

 through an opening at the apex and swim away 

 by means of a single ciliam placed at its anterior 

 end. The whole plant is thus converted into 

 a single sporangium. 



2. If the plant instead of being placed in water be only 



wetted, the zoospores do not swarm out of the 

 sporangium, but remain inside it, round themselves 

 off, and ultimately develop into new plants. These 

 were called germ-cells or gonidia by earlier 

 observers. 



3. If the soil becomes dry at the surface the contents 



of the green portion above ground pass down into 

 the rhizoids to form a large number of root-cells. 

 These may develop in three ways. 



a. If placed in water they develop zoospores at 



once. 



b. If placed on damp earth in the light they do 



not form zoospores, but, instead, each root- 

 cell puts out a rhizoid and develops into 

 a vegetative plant directly. 



c. If kept inside damp earth — in the dark, there- 



fore — the root-cells swell up and put out 

 rhizoids. The wall of the rhizoid just below 

 the cell becomes much thickened, and by its 

 growth in length the cell is carried up to 

 the surface of the earth. This cell is known 



