272 AQUATIC PHYCOMYCETES 



Parasitic on Ophiocytium (Sciadium) arbusculum in fresh and salt 

 water (in culture dishes), Germany. 



In attacked plants the plasma, nucleus, and chromatophore were 

 destroyed, the residue of the latter forming yellow-brown or dirty 

 red-brown clumps or granules in the cell. Staining was necessary to 

 demonstrate the full extent of the rhizoidal system. 



Rhizophydium schroeteri de Wildeman 



Mem. Herb. Boissier, 1900 (15): 5, fig. 3; Bull. Acad. Roy. Belg. (Sci.), V, 



17:289, fig. 3. 1931 



Sporangium sessile, spherical, ellipsoidal, or ovoid, up to 7 a in 

 diameter, with a prominent apical or subapical papilla, wall smooth, 

 colorless; endobiotic system very delicate, consisting of an unbranched 

 or once-branched rhizoid ; zoospores rarely more than twelve, spherical, 

 about 1 [j. in diameter, with an eccentric globule, escaping upon the 

 dissolution of the papilla, the wall of the empty urceolate sporangium 

 disintegrating after discharge; resting spore not observed. 



On the planktonic diatom Asterionella gracillima, coll. Schroeter, 

 Switzerland. 



Considered by Minden (1915: 326) to probably be a small form of 

 Rhizophydium sphaerocarpum, which it resembles in its general aspect. 

 One of the sporangia that de Wildeman (1931: fig. 3) illustrated is 

 borne on a short needle-like stalk. 



Rhizophydium oscillatoriae-rubescentis Jaag and Nipkow 

 Berichte Schweiz. Bot. Gesell., 61: 485, pi. 13, figs. 20-25. 1951 



Sporangium sessile usually lateral on the trichome, globose or broad- 

 ly ellipsoidal or pyriform, about 16-20u, in diameter, with broad round- 

 ed apex, finally subangular, with a papilla, wall smooth, hyaline; 

 rhizoid very delicate, unbranched, short or up to 180 p. long; zoospores 

 6-30, spherical, about 2.5-3.5 [jl in diameter with a basal hyaline glob- 

 ule and long flagellum; resting spore (not known with certainty to 

 belong to the species) spherical, thick-walled, 8-12 jj. in diameter with 

 a spherical male cell 4 ^ in diameter adherent to it. 



Parasitic on the planktonic alga Oscillatoria rubescens, Switzerland. 



