BLASTOCLA D I ALES 



133 



in which the final cleavage of the cytoplasm of the sporangium 

 has failed to occur. Such swarmspores have two or more nuclei. 



Key to Genera of Blastocladiaceae 



I. Thallus not differentiated into a stout main axis and more slender 

 brunelies, composed of cylindrical hyphae which are definitely and 

 usually frequently constricted; sporangia proliferating; thick-walled 

 resting sporangia unknown. 



1. Gonapodya, p. 134 



Fig. 49. — (a, h) Gonapodya siliquaeformis (Reinsch) Thaxter. (c-e) G. 

 polymorpha Thaxter. (a) Typical plant, segments short, sporangia proliferating. 

 (b) Sporangium freeing unicDiate swarmspores. (c) Segmented portions of 

 plant borne sub-umbellately on a slender hypha. {d, e) Sporangia showing 

 extreme variation in size of swarmspores. {After Thaxter 1895.) 



II. Thallus provided with a stout main axis bearing more slender branches; 

 thick-walled resting sporangia present. 



A. Thallus separated into definite segments by pseudosepta, some- 

 times slightly constricted at the septa. 



2. Allomyces, p. 135 



