SAPROLEGNIACEAE 15 



Family 10. SAPROLEGNIACEAE 



SCHROETER 93, 7:264, 9:345, II : 244, 14:450, 16:395, I/:5I9 



Mycelium strongly developed, broadly filamentous, more or less branched ; prop- 

 agation by zoosporangia, producing ciliate, rarely non-motile, zoospores ; sexual re- 

 production by antherids and oogones, their contents fusing by means of a connecting 

 tube. 



Key to the Subfamilies 



I. Vegetative mycelium broad, tubular, aquatic ; zoosporangia cylindric, of the same 



width as the mycelium 



1. Filaments uniform, not constricted Saprolegniae 



2. Filaments constricted regularly Leptomitae 



II. Vegetative mycelium thin, mostly saprophytic on plant tissues; zoosporangia sev- 



eral times broader than the filaments Pythiae 



Subfamily Saprolegniae 



SCHROETER 96 



Nutritive mycelium sunken in the substratum, finely branched, water mycelium 

 tubular, repeatedly branched, cylindric ; zoosporangia narrowly cylindric ; oogones 

 mostly terminal, globose, i- to many-spored, antheridia clavate, the tube penetrating 

 the oogone. 



I. Zoospores escaping before germination 



1. Zoosporangia cylindric-clavate, zoospores several- rowed 



a. Zoospores escaping together through a terminal pore 



(1) Zoospores scattering upon escape 



(a) Zoosporangia ovate Pythiopsis S. 97 



(b) Zoosporangia cylindric Saprolegnia 7: 268, S. 97 



(2) Zoospores remaining massed about the pore 



Achlya 7: 274, S. 99 



b. Zoospores not escaping through a common opening 



(1) Each zoospore escaping singly through its own lateral pore 



Dictyuchus 7:273, S. 99 



(2) Zoospores freed by the falling apart of the whole sporangium 



Thraustotheca S. 100 



2. Zoosporangia linear, zoospores i-rowed 



a. Zoospores scattering upon escape Leptolegnia S. 100 



b. Zoospores remaining in a ball at the pore 



Aphanomyces 7:276, S. 100 



II. Zoospores germinating in the sporangium 



Aplanes S. 101 



Subfamily Leptomitae 



SCHROETER 101 



Filaments thin, branched, divided by regular constrictions ; zoosporangia cylindric. 

 pear-shaped or elliptic ; oogones i-spored. 



I. Branches similar to the main stem 



