296 AQUATIC PHYCOMYCETES 



with that of the host filament, 5-11 u. high by 7-16 u. broad, with two 

 lateral opposite papillae (rarely one), wall thin, smooth, colorless; 

 rhizoidal system delicate, branched; zoospores ovoid or somewhat 

 rodlike, 3-6 (J-long by 2-3 u, in diameter, with an eccentric colorless glob- 

 ule and a short flagellum, escaping amoeboidly through one or two pores 

 formed upon the deliquescence of the papillae, movement a brisk gliding ; 

 resting spore sessile, polyhedral, six- to eight-cornered in optical sec- 

 tion, the corners often somewhat protruding, 6-7 u. in breadth, wall 

 thick, colorless, contents with few to many refractive globules, en- 

 dobiotic part consisting of a central, possibly branched, axis, ger- 

 mination not observed; companion cells one or two, spherical or ovoid, 

 3 u. in diameter, wall thin, smooth, colorless, attached directly to the 

 receptive thallus (resting spore), into which its contents are discharged 

 and from which after fertilization it is separated by a cross wall. 



Parasitic on Tribonema bombycina, Scherffel (be. cit.), Zygnema sp., 

 Berczi (1940: 81), Hungary; Sparrow (1936a: 439, fig. 2 a-j), Great 

 Britain; Sparrow (1943: 201, fig. 11 U-V), United States. 



As pointed out by Scherffel, the sporangia of this species are like 

 those of Rhizophydium transversum, which occurs on members of the 

 Volvocales, and of Phlyctidium irregulare, found on Hantzschia and 

 other diatoms. But the angular resting spore, formed after a sexual 

 process, and the host distinguish R. goniosporum from both these species. 



Scherffel noted that the parasite formed rose-red products of de- 

 composition in the host cell. These were not observed by Sparrow. 

 The American material differed from Scherffel's in having smaller 

 zoospores (3 by 2 ja as compared with 6 by 3 \x), which bore an anterior 

 rather than a basal globule. 



SECTION V 1 . 2 



Rhizophydium messanense Morini 



Malpighia, 10: 79, pi. 3, figs. 1-4. 1896 



(Fig. 17 Y, p. 228) 



Phlyctochytrimn messanense (Morini) Minden, Kryptogamenfl. Mark Bran- 

 denburg, 5: 339. 1911 (1915). 



1 See also the following imperfectly known species of Rhizophydium: 



R. coleochaetes, p. 315 R. hormidii, p. 316 



2 See R. palagicum and R. hohzontale Paterson {Mycologia, 50:85. 1958). 



