262 AQUATIC PHYCOMYCETES 



which arises from a short peglike axis rather than from a more elongate 

 slender thread. 



Rhizophydium uniguttulum Canter 

 Trans. Brit. Mycol. Soc, 37: 113, figs. 1-2, pi. 3, figs. 1-2. 1954 



(Fig. 10 G, p. 108) 



"Thallus monocentric epibiotic consisting of a sporangium and a 

 meagre, branched rhizoidal system just within host cell-wall. Sporan- 

 gium broadly ovoid, oval or globose, 3-13 [x broad and 4.5-15.5 u, 

 high, developed by direct enlargement of the zoospore; dehiscing by 

 deliquescence of the apex. Zoospore spherical, 2-2.5 [x in diameter, 

 with a single basal refractive globule and posterior fiagellum 12 u. long. 

 Resting spore formed after sexual fusion of a small male cell (an en- 

 cysted zoospore) which settles on and makes contact directly or via 

 a short tube with a slightly larger female cell; spherical (5.5-9.5 u,) 

 wall smooth, thick, surrounded by mucilaginous envelope; content 

 one large and a few smaller globules. Germination not observed" 

 (Canter, loc. cit.). 



Parasitic on Gemellicystis neglecta in the plankton, Great Britain. 



Here, as in a number of other parasites of phytoplankters, discharge 

 of the zoospores is accomplished by dissolution of a considerable part 

 of the sporangium wall. 



Rhizophydium ampullaceum (Braun) Fischer 

 Rabenhorst. Kryptogamen-Fl., 1 (4): 101. 1892 



Chytridium ampullaceum Braun Monatsber. Berlin Akad., 1855: 384; Ab- 

 handl. Berlin Akad., 1855:66, pi. 5, figs. 24-27. 1856. 



Olpidium ampullaceum (Braun) Rabenhorst, Flora Europaea algarum, 

 3: 282. 1868. 



Sphaerostylidium ampullaceum (Braun) Sorokin, Arch. Bot. Nord France, 

 2:20, fig. 17. 1883 (separate). 



Sporangium sessile or, rarely, on a short stalk, spherical, 6-8 \i in 

 diameter, with an apical discharge tube 4-5 ;x long by 2 \x in diameter, 

 wall thin, smooth, colorless; rhizoids feebly developed, branched; 

 zoospores with a single globule and a posterior fiagellum, discharged 

 through the somewhat flaring funnel-like apex of the opened discharge 

 tube; resting spore not observed. 



