CHYTRIDIALES 89 



2'. Sporangium lacking an oxtramatrical 

 stalk. 



a'. Swarmsporcs freed through an 

 apical opening. 

 1". Sporangium opening by a 

 large lid; resting spore 

 formed bj' a definite 

 sexual process in which 

 a male individual sends 

 a fertilization tube into 

 a female individual. 

 4. Zygorhizidium, p. 93 

 2". Sporangium not opening 

 by a lid. 



a". Contents of spor- 

 angium escaping 

 into a thin-walled 

 vesicle in which 

 the swarmspores 

 are then formed. 

 6. Rhizidiomyces, p. 93 



b". Swarmspores for- 

 med in the 

 sporangium. 

 1'". Swarm- 

 spores 

 encysting 

 at the 

 mouth of 

 the spor- 

 a n g i u m 

 as in 



Achlya. 



6. Achlyella, p. 94 



2'". Swarm- 

 spores es- 

 c aping 

 without 

 encyst- 

 ment. 



7. Phlyctochytrium, p. 94 

 b'. Swarmspores freed through a 



basal or subbasal opening. 

 1". Sporangial wall spiny. 



8. Asterophlyctis, p. 94 

 2". Sporangial wall smooth. 



a". Mycelial threads 

 drawn out to 

 extremely slen- 

 der tips. 



9. Rhizoclosmatium, p. 94 



