CLASS ARCHIMYCETES 



27 



(Fig. 15, 3), push toward the periphery and, after completing a nuclear 

 division, cut up the protoplasm next the wall into uninucleate zoospore 

 initials. These grow with equal rapidity, fill out the sporangium and 

 thereupon contract, perhaps by the expression of water. Finally they 

 begin to swarm from the emission collar (A. Fischer, 1882; Schwarze, 

 1922). 



The formation of hypnospores in the poorly nourished hyphae is 

 preceded by a sexual act. Around one larger multinucleate protoplast, 

 one or more equally nucleate, smaller male protoplasts are placed (Fig. 

 15, 6). Each is surrounded by a membrane which in the female cell, 

 except for the point of contact with the male, is thickened and echinulate 



while the male remains thin and smooth. 

 At fertilization the separating wall dissolves 

 and the whole content of the male cell passes 

 into the female (Fig. 15, 7). If several 

 male cells are present, apparently all can 

 discharge their content into the female. 



Fig. 16. — Pscudol pidium Saprolegniae. a, swollen host hyphae with 3 sporangia; b, 

 hypnospore. (X 320; after A. Fischer, 1882.) 



The empty male cell membranes remain connected to the zygote as 

 " appendiculate cells." The further fate of the nuclei is unknown. The 

 endospore becomes brown and thickened while the echinulate exposore 

 remains hyaline. They germinate by zoospores which discharge through 

 an emission collar (Barrett, 1912). 



Pseudolpidium Saprolegniae, also parasitic on Saprolegnia, in structure 

 and habit resembles Olpidiopsis but differs in the absence of "appendicu- 

 late cells" on the hypnospores (Fig. 166). An insufficiently known spe- 

 cies found by Serbinov (1907) on algae, suggests Woronina and Rozella 

 in the peculiarity of its young amoeboid protoplasts, which divide by 

 constriction. 



The species of Wo7-onina are parasitic on algae and fungi. In W. poly- 

 cystis, on Saprolegnia (A. Fischer, 1882), the zoospore on the host hyphae 



