AQUATIC PHYCOMYCETES 



Fig. 87. Pythium 



A. Pythium undulatum Petersen; internally proliferous sporangia. B-C. 

 Pythium vexans de Bary: B, sexual apparatus, showing aplerotic oospore and 

 monoclinous bell-shaped antheridium broadly applied to oogonium; C, 

 sporangium. D-E. Pythium echinulatum Matthews: D, spiny oogonia with 

 stalked and sessile (hypogynous) antheridia; £, intercalary sporangium form- 

 ing zoospores in vesicle. F. Pythium pulchrum Minden, sexual stage; left 

 one with monoclinous and right one with hypogynous antheridium. G. Pyth- 

 ium de baryanum, sexual stage, showing a monoclinous arched antheridial 

 stalk and a branched diclinous one bearing two antheridia. H. Pythium 

 ultimum Trow, sexual apparatus, showing single antheridium, which in this 

 species is typically monoclinous and arises immediately below oogonium. 



(A, Goldie-Smith, 1952, from photomicrograph; B, C, F-H, Middleton, 

 1943; D, E, Matthews, 1931). 



