814 AQUATIC PHYCOMYCETES 



is directed forward while the posterior one is dragged along behind. 

 Sexual reproduction is by oogonia and antheridia; oogonia 11-18.5 \l 

 thick, spherical, containing one egg, which does not completely fill the 

 oogonium ; eggs 9-1 5 \l thick, spherical, when mature surrounded by a 

 thick wall and a small amount of periplasm; antheridium spherical, 

 about 5 \i thick, emptying its entire contents through a delicate tube 

 into the egg" (Couch, he. cit.). 



Parasitic in the hyphae of Pythium gracile and P. dictyosporum, 

 United States. 



The type species of the genus. See remarks under Pythiella. 



Pythiella besseyi (Sparrow and Ellison), comb. nov. 

 Ectrogellabesseyi Sparrow and Ellison, Mycologia, 41 : 33, figs. H-M. 1949. 



Sporangium irregularly tubular, often lobed, sometimes ellipsoidal, 

 27-42 [j. long by 13-17 jjl in diameter, one to several in a host cell, 

 forming one to several discharge tubes of varying length; zoospores 

 numerous, delimited within the sporangium, upon discharge from the 

 sporangium encysting and forming motionless clusters at the orifice of 

 the discharge tube, emerging from the cyst as a laterally biflagellate 

 zoospore, 5 by 2.5 [j.; resting spores not observed. 



Parasitic in thalli and sporangia of Olpidiopsis schenkiana, United 

 States. 



See remarks under Pythiella. 



EURYCHASMA Magnus 



Hedwigia, 44: 347. 1905 

 (Fig. 61, p. 818) 



Thallus at first wholly endobiotic, at maturity bursting the distended 

 host wall and becoming partly extramatrical, holocarpic, unbranched; 

 sporangium with from one to several extramatrical discharge tubes, 

 zoospores encysting within the sporangium or directly on emerging, 

 laterally biflagellate; resting spore not observed. 



So far as is known, this fungus occurs exclusively on marine algae. 



See the remarks under Ectrogel/a, above. 



