SAPROLEGNIALES 809 



Ectrogella perforans H. E. Petersen 



Oversigt Kgl. Danske Vidensk. Selskabs. Forhandl., 1905(5): 466, fig. VII, 1-5 



(Fig. 60 G-J, p. 806) 



Sporangium spherical, lenticular, or rarely irregularly saccate, 26-40 \x 

 long by 20-35 \l in diameter, with a thin colorless wall, discharge tubes 

 from one to five, broadly conical, 8-10 \i long by 9-12 y. in diameter; 

 zoospores pyriform, 3 \i long by 2 \x wide, somewhat curved, with an 

 anterior refractive droplet, the two flagella anteriorly (?) attached and 

 oppositely directed, emerging individually through the large orifice of 

 the discharge tube and swimming away immediately, movement an 

 uneven rotation; resting spore spherical, 14-19 \i in diameter, with a 

 smooth colorless double wall, 2.5-3 \i thick, the outer wall thin, the 

 inner thicker, contents with globules, germination not observed. 



Parasitic in Licmophora lyngbyei (abbreviata?), Synedra ulna {?), 

 Petersen (loc. cit.), Licmophora sp., Sparrow (1934c: 19, pi. 4, figs. T-Y), 

 Denmark; Striatella unipunctata, Licmophora abbreviata, Sparrow 

 (1936b: 239, pi. 3, fig. 2), Licmophora abbreviata, L. flagellata, Karling 

 (1942e: 21), United States; Licmophora spp., Striatella unipunctata, 

 Podocystis adriatica, and probably Thalassionema nitzschioides, Aleem 

 (1950c: 713, figs. 1-2), Licmophora spp., Striatella unipunctata, Po- 

 docystis adriatica, Aleem (1950d:423, figs. 1-4), France; Licmophora 

 abbreviata, L. gracilis, Striatella unipunctata, Lauderia borealis, Synedra 

 tabulata, Aleem (1953: 18, figs. 34-42, pi. 1, fig. 4), Sweden. 



With respect to zoospore flagellation, Aleem (1953) agreed with 

 Petersen that in the moving spore only a single posteriorly directed 

 flagellum is present. Earlier, Hohnk (1939) had insisted that the normal 

 zoospore is posteriorly uniflagellate, although he admittedly had seen 

 biflagellate ones. All this is at variance with the present author's 

 repeated observations that the spores are biflagellate. It is, of course, 

 entirely possible that two different fungi are involved, both of which 

 were attacking the same host simultaneously. If so, the uniflagellate 

 fungi reported by Petersen, Aleem, and Hohnk belong to Pleotrachelus 

 and the biflagellate forms to a species of Ectrogella. 



In most instances the discharge tubes gain access to the outside 

 because the valves of the host are forced apart by the thallus of the 



