SAPROLEGNIALES 827 



and resting spore, differs in two important features: (1) in having a 

 septate thallus and (2) in lacking the "Spriezapparat," or thick-walled 

 spreading apparatus at the base of the evacuation tube which forces 

 the valves apart. 



Because of its septate thallus his fungus cannot be included in the 

 Ectrogellaceae as defined by Scherffel (1925a: 6) and probably repre- 

 sents the type of a new genus. Tokunaga's description is quoted here: 



Thallus endobiotic, at first consisting of a cylindrical, unbranched tube, 

 later richly branched, provided with long or short, often somewhat inflated 

 twigs, septate at indefinite intervals into a number of cells at maturity, with- 

 out prominent constriction at the septum, each component cell functioning 

 as a sporangium or an oogonium; sporangia cylindrical or tubular, unbranch- 

 ed, or irregularly branched, often lobed, widely variable in length, up to 

 150 [j. long, 4.8-16.8 y. in diameter; exit-tubes single for a sporangium, very 

 long, up to 150 u, in length, about 4.8 \l in breadth; zoospores on leaving the 

 sporangium coming to rest at once in a hollow sphere at the mouth of the 

 exit-tube, encysting there as in Ac/ilyo, later swimming away leaving their cyst 

 behind, in encysting globular, 6-7.2 \i in diameter, in swimming kidney-shaped, 

 narrower in front, provided with two cilia near the hilum, containing an oil 

 drop; oogonia (?) intermixed with sporangia in a thallus, terminal or inter- 

 calary, cylindrical, medially expanded, 15.6-21.6 [x in breadth, provided with 

 no periplasm; antheridia absent; oospores (?) one or two, lying loosely in 

 an oogonium, spherical, 14.4-19.2 u. in diameter, with smooth, thick mem- 

 brane and a large oil globule, germination unknown. 



Tokunaga's fungus occurs on Surirella sp. and Navicula sp., Japan. 



The septate fungus figured by West and West (1906: 99, pi. 11, fig. 9) 

 on Pleurotaenium ehrenbergii from Ireland and the Outer Hebrides 

 resembles Tokunaga's fungus in structure and Aphanomycopsis desmid- 

 iella in host. West and West say that it was this organism which caused 

 Archer (1860: 215) to claim that zoospores were formed by desmids. 



A lone specimen of the fungus described by Friedmann (1952: 200, 

 fig. 5, k) on Pinnularia viridis from Austria, possessed a cross wall in 

 the thallus. He speculated that it might be transitional between the 

 typical nonseptate condition and the much-septate Japanese form. 



Aphanomycopsis desmidiella Canter 

 Trans. Brit. Mycol. Soc, 32: 166, figs. 2-3. 1949 

 (Fig. 63 G-H, p. 824) 

 Thallus endobiotic, branched, holocarpic, nonseptate, 410 u. long by 



