HYPHOCHYTRIALES 753 



Parasitic on eggs and oospores of aquatic Phycomycetes and on 

 green algae ; saprophytic on pollen bait in soil. 



KEY TO THE SPECIES OF RHIZIDIOMYCES 



Sporangium wall persistent after discharge; on eggs and oospores of 



other aquatic Phycomycetes or saprophytic in soil on pcllen bait 



Sporangium apophysate; on eggs and oospores of other aquatic 



Phycomycetes R. apophysatus, p. 754 



Sporangium nonapophysate ; saprophytic in soil 

 Wall of sporangium smooth 



Zoospores 5.5-6 by 7-8 u; protoplasm colorless 



R. bivellatus, p. 754 

 Zoospores 4-4.5 by 5.5-6.5 ;jl; protoplasm yellowish to orange 



R. hansonii, p. 755 

 Wall of sporangium covered by unbranched setae . . R. hirsutus, p. 756 

 Sporangium wall evanescent after discharge; on Chlamydomonas . . . 



R. ichneumon, p. 756 



Explanation of Figure 55 



A-D. Latrostium comprimens Zopf in oogonia of Vaucheria: A, sporangium 

 within oogonium, resting on surface of egg of host; the delicate rhizoids are 

 within egg; B, sporangium with large papilla laterally placed with respect to 

 rhizoidal axis; C, discharging sporangium; D, anteriorly uniflagellate zoo- 

 spore. E-G. Rhizidiomyces apophysatus Zopf on oogonia of Achlya: E, mature 

 apophysate sporangium with discharge tube; F, sporangium with contents 

 emerging into vesicle formed at tip of discharge tube; G, mature zoospores 

 formed outside sporangium. H-l. Hyphochytrium infestans Zopf on ascocarp 

 of Helotium: H, intercalary sporangium, showing discharge papilla; /, terminal 

 apiculate sporangium discharging its anteriorly uniflagellate zoospores through 

 a lateral pore. J-L. Anisolpidium ectocarpii Karling in Ectocarpus: J, resting 

 spore and empty sporangium in hypertrophied host cells; K, zoospore; L, 

 zoospores emerging. M. Rhizidiomycopsis japonicus (Kobayashi and Ookubo) 

 Sparrow on oogonium of A planes sp., empty sporangium and one discharging 

 fully formed zoospores. N-O. Canteriomyces stigeoelonii (de Wild.), comb. 

 nov., in Stigeoclonium: N, emergence of protoplasm from sporangium; O, 

 protoplasm starting to emerge. 



(A-D, Zopf, 1894; E-I, Zopf, 1884; J-L, Karling, 1943; M, Kobayashi and 

 Ookubo 1954b; N-O, Canter, 1950b) 



