218 



PRACTICAL BOTANY 



Sometimes living fish that are confined in close quarters become 

 infested with this mold and die. In such cases the mold is 

 first a parasite, but upon the death of its host it becomes a 

 saprophyte. In late summer and early autumn, flies and other 

 insects often become infected with water molds and related 

 fungi (as Entomopktliora). If these insects, when found lying 

 on the floors and window sills, are placed 

 in a dish of water, the mold sometimes 

 grows rapidly, soon producing a "collar" 

 of fluffy hyphse about the thorax of the 

 insect, and may cover the entire body 

 (Fig. 177). 



206. Water mold: vegetative structures 

 and nutrition. The mycelium of Sapro- 

 legnia branches and extends itself through- 

 out the tissues of its supporting material. 

 As in Mucor and Vaucheria, the plant is 

 a coenocyte. It absorbs its food material 

 directly, and when the supply of food is 

 abundant it may grow with striking ra- 

 pidity. This plant is effective in bring- 

 ing about decay of dead animal bodies in 

 the water. 



207. Water mold: asexual reproduction. 

 At times the numerous hyphse which 

 extend from the nourishing material may 

 form transverse walls, which separate large 



swollen tip segments from the bases of the hyphse. Within each 

 tip segment many zoospores form (Fig. 178). These escape 

 into the water in very large numbers and swim about quite 

 actively. Upon coming in contact with favorable nutriment the 

 cilia are withdrawn and the zoospore germinates into a new 

 hypha, which by growth may produce a new mycelium. 



208. Water mold : sexual reproduction. From the tips of 

 short hyphae large spherical cells (oogonia) are formed, in 

 each of which one to many eggs are produced. In some 



FIG. 178. A water mold 

 bearing a sporangium 

 (s), from which zoo- 

 spores (z) are escaping 



After Schenck 



