LAG EN IDl ALES 947 



distal end slightly constricted subterminally; zoospores numerous, es- 

 caping at the dissolution of the tip of the discharge tube, exhibiting 

 imperfect diplanetism, with two apically inserted flagella, one 7.5-9 (jl 

 the other 5.5-7 u, long, with a spherical droplet, during the first swarming 

 period 4.5-5 u. long by 2-3 \x broad, after undergoing a period of rest 

 and halting motion, in the second swarming period 4-4.5 \x long by 

 3-3.5 \x broad, resting spore not observed. 



On Pleurosigma attenuation, Cocconema lanceolatum, Nitzschia sp., 

 N. sigmoidea, coll. Gill, de Wildeman (1896b: 42), Great Britain; 

 parasitic in Gyrosigma attenuation and G. acuminatum, Friedmann (Joe. 

 cit.), Austria. 



Unless host specificity is proven in the future, there can be little doubt 

 but that Gill's and Friedmann's fungi are the same. Friedmann states 

 that van Heurck's (1899) Figure 2 is based on Gill's material. 



Olpidiopsis schenkiana Zopf 

 Nova Acta Acad. Leop.-Carol., 47: 168, pi. 15, figs. 1-32. 1884 



Pleocystidium parasiticum Fisch, Sitzungsber. Phys.-Med. Soc. Erlangen, 

 16:67, pi. 1, figs. 24-39. 1884. 



Olpidiopsis parasitica (Fisch) Fischer, Rabenhorst, Kryptogamen-Flora, 

 1 (4): 40. 1892. 



Diplophysa schenkiana (Zopf) Schroeter, Engler und Prantl, Die Nat. 

 Pflanzenf., I, 1 : 85, fig. 68, A-D. 1892 (1897). 



Pseudolpidiopsis schenkiana (Zopf) Minden, Kryptogamenfl. Mark Branden- 

 burg, 5:257. 1911 (1915). 



Pseudolpidiopsis parasitica (Fisch) Minden, loc. cit., p. 258. 



Sporangium broadly or narrowly ellipsoidal, rarely spherical, often 

 somewhat curved, 32-41 by 17 jjl, wall thin, smooth, colorless, discharge 

 tube usually single, fairly broad, variable in length, often long and 

 tortuous, arising laterally on ellipsoidal sporangia, occasionally causing 

 swelling of the infected cell ; zoospores from eight to fifty, grape-seed- 

 like, biflagellate, with refractive colorless globules in the plasma, 8 by 

 7 \i, formed in the sporangium and either emerging through the tube 

 and swimming directly away or first undergoing amoeboid motion at 

 the orifice and without encystment being directly transformed into the 

 secondary zoospore, which swims away; resting spore spherical or 



