244 AQUATIC PHYCOMYCETES 



soid or broadly discoid gelatinous vesicular host mass, 32-58 u, in diam- 

 eter, with broad apical papilla, thin smooth hyaline wall; rhizoid 

 delicate, simple or sparingly branched, undulate; zoospores spherical, 

 2.5-3.5 (jl in diameter, with a hyaline globule and long flagellum, 

 emerging through a tube 6 \l long by 4.5 \l wide in the gelatinous 

 material formed by the deliquescence of a papilla, at once motile. 



Parasitic on the planktonic alga Oscillatoria rubescens, Switzerland. 



Although not well marked morphologically this species is remark- 

 able in the reaction it produces on the host. Infected trichomes secrete 

 large amounts of slime and eventually curl up to form a tight slimy 

 capsule completely hiding the fungus. The authors suggest the term 

 "ring disease" ("Ringelkrankheit") for the epidemic. 



Rhizophydium subangulosum (Braun) Rabenhorst 



Flora Europaea algarum, 3 : 281. 1868. Non R. subangulosum sensu Dangeard, 

 Bull. Soc. Linn. Normandie, III, 9: 88. 1884-85, et auct. recent. 



(Fig. 17 B, p. 228) 



Chytridium subangulosum A. Braun, Monatsber. Berlin Akad., 1855: 382; 

 Abhandl. Berlin Akad., 1855: 44, pi. 3, figs. 27-31. 1856. 



Sporangium sessile on the apical or other cells of the trichome of 

 the alga, spherical at first but at maturity, upon the formation of 

 from two to three papillae, becoming somewhat angular, 10-25 \i in 

 diameter, wall slightly thickened, smooth, colorless; endobiotic system 

 consisting of a delicate sparingly branched or occasionally unbranched 

 rhizoid; zoospores spherical, 2-2.5 jj. in diameter, with a colorless 

 basal globule and a long flagellum, escaping through several pores 

 formed upon the deliquescence of the papillae; resting spore not ob- 

 served. 



On Oscillatoria tenuis var. subfusca, Braun (loc. cit.), (?) germinating 

 spores of Aspidium, Schenk (1858b: 8), isolated from soil, Reinboldt 

 (1951: 178), Germany; Oscillatoria sp., Sparrow (1936a: 442, pi. 17, 

 fig. 3), Lyngbya sp., Ingold (1949:442), Great Britain; Oscillatoria 

 tenuis, Berczi (1940: 83), Hungary; Aphanizomenon gracile, possibly 

 Oscillatoria agar dim, Fott(1950:7, fig. 19), Czechoslovakia; Oscil- 

 latoria rubescens, Jaag and Nipkow (1951 : 485, figs. 26-28), Switzer- 



