24 THE SAPROLEGNIACEAE 



Antheridia on all or nearly all the oogonia; androgynous or rarely diclinous 



Oogonia commonly on short, lateral branches, spherical with a neck, eggs 



usually five or more in an oogonium, 16-22^ thick 5. monoica (7) 



As in 5. monoica, except that the eggs are usually less than five in an oogonium 



and mostly 25-27M thick 5. monoica var. glomerata (8) 



As in 5. monoica, but no oogonia produced except in a solution of lucin and levu- 



iQgg S. monoica var. vexans (9) 



As in 5. monoica except that the oogonia have longer stalks and few or no pits, 

 and that the vegetative threads are longer and more slender 



S. monoica var. moniana (p. 75) 

 Oogonia commonly on rather short lateral branches or also intercalary, spheri- 

 cal to barrel-shaped or even thread-like with a row of eggs; eggs 25-27^ 

 thick in larger oogonia, 17-22M thick in small ones; antheridial branches 



at times containing eggs S. paradoxa (p. 75) 



Eggs large; than above, most about 30-33M thick, not often single 



S. lit oralis (10) 



Eggs still larger, most about 38^ thick, very often single 5. megasperma{ll) 



Oogonia absent; parasitic on fish, etc. (position doubtful) 5. parasitica (12) 



Hypogyna Group: Oogonia not in chains, their walls with conspicuous pits. An- 

 theridia on all or nearly all the oogonia, androgynous, normally formed from a cell 

 cut off from the oogonial stalk immediately beneath the oogonium. .5. hypogyna (13) 

 Torulosa Group: (Position doubtful; may go properly in Isoachlya); oogonia in large part 



is. torulosa (14) 

 5. rhaetica (p. 67) 

 5. variabilis (p. 67) 



Sub-genus Pseudosaprolegnia: Eggs as a rule only one or two in an oogonium, subcen- 



tric, i. e., with the protoplasm completely surrounded by small oil drops which are 



in a double layer on one side and a single layer on the other. Oogonia covered with 



blunt papillae. 



Asterophora Croup: There is but one species in the subgenus 5. asterophora (15) 



* 



Artificial key to the Species 



I. Oogonia absent; parasitic on fish 5. parasitica (12) 



1. Oogonia present 



2. Spores very large (25^ thick) ; oogonia formed within the substratum 



S. curvata (p. 72 ) 



2. Not as above; oogonium covered with blunt papillae; eggs only 1-3 in an oogonium 



5. asterophora (15) 



2. Not as above; eggs 9-30 in an oogonium; 25-27M thick; antheridial branches at times 



containing eggs 5. paradoxa (p. 75) 



2. Not as above in all respects 3 



3. Oogonia in chains, androgynous antheridia on each oogonium 



See Aplanes androgynus {p. 77) 



3. Oogonia in chains, easily separating, antheridia absent 



See Isoachlya monilifera (p. 88) 



♦American species are followed by a number, others by a page reference. 



