994 AQUATIC PHYCOMYCETES 



capable of multicellular development under less restricted environmen- 

 tal conditions and, hence, is not comparable with truly one-celled, 

 dioecious forms. 



Zopf observed that, because of the many zoospores, widespread 

 infection of new pollen could be induced under laboratory conditions 

 within twenty-three hours. 



Lagenidium rabenhorstii Zopf 



Sitzungsber. Bot. Vereins Prov. Brandenburg, 20: 77. 1878; Nova Acta 

 Acad. Leop.-Carol., 47: 145, pi. 12, figs. 1-28, pi. 13, figs. 1-9. 1884 



(Fig. 81 D, p. 1002) 



Thallus of small extent, occupying a single cell of host, cylindrical or 

 with frequent irregularities and with short or long often clavate, 

 straight, crooked, or irregular branches 2.5-8 [i in diameter, occasion- 

 ally somewhat irregularly saccate; sporangia from one to ten, generally 

 from five to seven, delimited by narrow sometimes slightly constricted 

 septations, variable in shape, with a cylindrical or slightly conical 

 discharge tube which is rarely locally constricted when passing through 

 the host wall and which projects only slightly extramatrically; zoospores 

 reniform, 8.5 \x long by 6 \x wide, laterally biflagellate, formed in a 

 vesicle at the orifice of the discharge tube; plants dioecious or, less 

 frequently, monoecious, female gametangium intercalary, lateral or 

 terminal, expanded, spherical, ovoid, fusiform, or irregular, 15-16 \x 

 wide; male gametangium resembling the sporangium or occasionally 

 somewhat crook-necked, laterally applied, with a fertilization tube; 

 oospore spherical, with a smooth colorless double wall, lying loosely 

 in the gametangium, 10.4-20 \l in diameter, with a fairly large nearly 

 centric globule, germination not (?) observed. 



Parasitic in vegetative cells of Spirogyra sp., Mougeotia sp., etc., 

 Zopf (/or. cit.), Schroeter (1885: 227), Minden (1915: 434), Germany; 

 (?) Spirogyra sp., de Wildeman (1895b: 98, figs. 1-2), France; Spirogyra 

 sp., Constantineanu (1901:379), Rumania; Spirogyra sp., Scherffel 

 (1914: 17), Spirogyra sp., Zygnema sp., Domjan (1936: 51, pi. 1, figs. 56, 

 94, 174), Spirogyra sp., Berczi (1940:86), Hungary; Spirogyra sp., 

 Atkinson (1909a: 329, fig. 5 A-B), 5. orthospira, Oedogonium plusio- 



