LEPTO MIT ALES 899 



in diameter; zoospores as in other species, 13-14 by 10-11 u,; anther- 

 idium irregularly spherical, strikingly large, curved around and adnate 

 to the oogonium at the apex, 27-70 u. long by 7-11 \x broad, arising 

 from a narrow tortuous short branched diclinous filament produced 

 from the basal cell; plant monoecious; oogonium somewhat pyriform, 

 45-57 u, broad by 57-62 u. long with a broad rounded top and a 

 narrow stalklike unconstricted attenuated base, wall moderately thick, 

 somewhat wrinkled at maturity, arising from a short somewhat spiral- 

 ly twisted basally constricted stalk produced from the basal cell; 

 oospore large, spherical, 33-43 u. in diameter, very thick walled, the 

 outer wall sculptured as in the other species. 



On fruits and twigs, occurring with Blastocladia spp. and Rhipidium 

 interruption, Germany; submerged fruits, tomato fruits, Shen and Siang 

 (1948: 198, fig. 10), China. 



This truly remarkable species has been seen only once since Minden's 

 time. He regarded it as a connecting link between Rhipidium and 

 Sapromyees, its habit and oospore resembling the former genus, its 

 oogonia and whorled sporangia, the latter. 



Rhipidium americanum Thaxter 



Bot. Gaz., 21 : 327, pi. 21, figs. 1-15. 1896 



(Fig. 71 A-C, p. 894) 



Thallus and arrangement of reproductive organs (except the anther- 

 idia) as in Rhipidium interruptum, not significantly different in size; 

 sporangia 30-90 \x long by 20-46 \i in diameter; zoospores laterally 

 biflagellate, reniform, 10-12 u. long, contents with numerous refractive 

 granules; antheridium broadly clavate, 11-14 \x wide, androgynous, 

 borne on a short arched branch which arises immediately below the 

 oogonium ; oogonium 33-55 u. in diameter ; oospore 28-46 u. in diameter, 

 the heavy wall colorless or pale golden and ornamented as in Rhipidium 

 interruptum, germination not observed. 



In dense gummy pustules or mats. On various vegetable materials. 

 Thaxter (be. cit.), fruits of Crataegus, rose, apple, Kanouse (1927: 343, 

 pi. 48, fig. 38 a-c), apples, Crataegus, Sparrow (1932b: 297, pi. 8 a-b; 

 1933c: 532), twigs, Sparrow and Barr (1955: 555), United States; 



