424 AQUATIC PHYCOMYCETES 



KEY TO THE SPECIES OF SIPHONARIA 



Sporangium smooth-walled 

 Discharge pore basal ; zoospores with a small rust-colored globule 



S. variabilis, p. 424 

 Discharge pore apical; zoospores with a large hyaline globule 



S. sparrowii, p. 425 

 Sporangium beset with solid spines S. petersenii, p. 425 



Siphonaria variabilis H. E. Petersen 



Journ. de Botanique, 17: 220, figs. 11-17. 1903 



(Figs. 4 V-W, p. 72; 27 F, p. 428) 



Sporangium subglobose or broadly reniform, with a prominent basal 

 papilla, widely variable in size, 12-39 \x in diameter by 11-36.4 u. in 

 height (rarely 42 \x high by 38 u. in diameter), wall thin, smooth, color- 

 less ; rhizoids well-developed, stout, thick-walled, wide-lumened, branch- 

 ed, extending from the inconspicuous apophysis formed behind the 

 downward-tilted discharge papilla; zoospores numerous, somewhat pyri- 

 form, or ovoid, the narrower end anterior, 5 \x long by 2.5 u. in diameter, 

 the plasma bearing a laterally placed rust-colored globule and a larger 

 hyaline spherical body, flagellum from four to five times the length of 

 the body, movement darting, amoeboid usually only after partial or 

 complete retraction of the flagellum ; resting spore broadly ellipsoidal 

 or reniform, contents coarsely granular, with globules, 13-15.6 u. high 

 by 15.6-18.2 u, in diameter, with a brown, smooth, or slightly crenulated 

 wall, 2-2.5 fi. thick, borne like the sporangium, rhizoidal system less 

 extensive, germination not observed; contributing thallus (sometimes 

 two) somewhat obpyriform, 7-1 1 u, high by 5-8 \x in diameter, rhizoidal 

 system limited in extent. 



Saprophytic in empty submerged exuviae of Phryganeidae, Petersen 

 (be. cit.\ 1909:412, fig. 21b, d; 1910: 547, fig. 21 b, d), Sparrow (1937a: 

 32, fig. 2 a-j, pi. 1, figs. 1-12, pi. 4, figs. A-C), Denmark; Odonata 

 (Anisoptera) (dragonflies), Ephemerida (mayflies), Sparrow (1937a: 32), 

 exuviae of various aquatic insects, Sparrow (1952d: 768), United 

 States; exuviae of insects, Karling (1945d: 586), Brazil; exuviae, 

 Canter (1953: 290), Great Britain. 



The early stages in the development of this species need further study. 

 The small size of the parts renders interpretation of details susceptible 



