242 



THE FUNGI 



but is not uncommon in other genera, as Mucor and Sporo- 

 dinia. Two short branches from the mycelium become applied 

 to one another, end to end (Fig. 213, A). The tip of each then 

 becomes cut off as a sexual cell, or gamete (Fig. 213, B, C), 

 peculiar in having very many nuclei, and consequently called a 

 ccenogamete. The two gametes finally fuse, and a large zygo- 

 spore (Fig. 213, D) with heavy black walls is formed between 



FIG. 212. The sporangium of the bread mold (Rhizopus nigricans) 



A, young sporangium, showing dome-shaped cross wall (columella) shortly after its 

 formation; B, mature sporangium, the columella being hidden by the spores; 

 C, diagram of a lengthwise section of a sporangium ; s, spore cavity ; c, col- 

 umella. D, columella after the rupturing of the sporangium wall, which was 

 attached along the line a corresponding to similar line in B ; clusters of 

 spores still clinging to the columella 



the filaments. It is probable that the sexual nuclei from the 

 two gametes fuse in pairs within the zygospore. 



262. The water molds. The water molds (order Saprolegni- 

 ales) are very remarkable aquatic fungi which grow on the dead 

 bodies of insects when immersed in pond or ditch water (Fig. 

 214, A). Certain species attack the gills and mouths of young 



