42 



INTRODUCTION TO PLANT GEOGRAPHY [CHAP. 



producing one to a few flagellated swarm-cells. These, following a 

 period of swimming and often of division, become Amoeha-Vike, and 

 after feeding and further division behave as gametes, fusing in pairs 

 to form zygotes. The zygotes may grow each into a single Plas- 

 modium, or numerous zygotes or plasmodia may fuse together, or 

 one Plasmodium may divide into two or more. 



.'^? l 



FiG. lo. — Slime-moulds (Myxomycetes). A, Plasmodium of Didymiuin ( ■ i); 

 B, Sporangia of Hemitiichio ( < 15); C, Comotricha ( 20); D, Trichani[}hora 



(X 10). 



Whereas for spore-formation the plasmodium will usually creep 

 to a light and airy place, in general Slime-moulds are found on 

 decaying vegetable matter in moist and shady situations. Thus they 

 are very widespread in damp woods and thickets, though scarcely 

 ever forming any appreciable feature of local vegetation. If the 



