432 AQUATIC PHYCOMYCETES 



Saprophytic in empty submerged exuviae of Phryganeidae, H. E. 

 Petersen {he. cit.; 1909:415, fig. 21c; 1910:548, fig. 21c), Sparrow 

 (1937a: 38, text fig. 2 k-o, pi. 2, fig. 19), Denmark; Chironomidae 

 (midges), Odonata (Anisoptera) (dragonflies), Ephemerida (mayflies), 

 Phryganeidae (caddis flies), Sparrow (1937a: 38, pi. 2, figs. 18, 20-24, 

 pi. 4, figs. G-H), exuviae of various aquatic insects, Sparrow (1952d: 

 767), United States; Chironomidae, Sparrow (1936a: 418; 1937a: 38), 

 exuviae, Canter (1953: 290), Great Britain; insect integument, Spar- 

 row (1952a: 39), Cuba. 



The most ubiquitous of the exuviae-inhabiting chytrids. 



A form with larger sporangia and smaller zoospores, each with a 

 rusty-red globule, has been segregated from Rhizoclosmatium globosum 

 as R. aurantiacum Sparrow (1937a: 40). Although the colorless form 

 is most frequent it is difficult to say which one should be considered 

 the type of R. globosum. Petersen's attitude (comm. 1938) is that there 

 is no difference between the colored and colorless individuals and that 

 "... the coloration in most cases is due to age or to several external 

 factors." The original description includes both forms. In view of the 

 observed constancy of coloration in other chytrids, it is believed here 

 that the colored globule in this species is due to a genotypic factor. 

 Since colored and colorless types have been found in the same exuvia 

 where they would receive equal illumination, light does not seem to be 

 a factor in calling forth pigmentation. One other interpretation remains, 

 namely, that these two types are gametangia and that the larger, color- 

 less swarmers are female, and the smaller pigmented ones male gametes. 



Rhizoclosmatium aurantiacum Sparrow 



Proc. Amer. Phil. Soc, 78 (1): 40, pi. 2, figs. 14-17. 1937 



(Fig. 27 G, p. 428) 



Rhizoclosmatium globosum H. E. Petersen, pro parte, Journ. de Botanique, 

 17:216. 1903. 



Sporangium globose, 27-38 (x in diameter, with a smooth double- 

 contoured colorless wall; rhizoids extensive, branched, delicate, arising 

 as stout branches from the narrower ends of a broadly fusiform trans- 

 verse subsporangial apophysis; zoospores somewhat ellipsoidal, 2.5 [i 



