CHYTRIDIALES 501 



attack seven other kinds of Phycomycetes in the same culture nor the 

 filamentous and unicellular algae that were also present. 



Chytridium surirellae Friedmann 

 Osterr. Bot. Zeitschr., 100: 7, rig. 1. 1953 



Sporangium obpyriform, 10.5-18.5 \x long by 9-15.5 \x in diameter, 

 with a thin, smooth, colorless wall, resting on a short rigid extramatrical 

 stalk which in most cases projects slightly into the interior of the spo- 

 rangium ; rhizoidal system consisting of a few delicate bushy branches 

 which terminate the unbranched intramatrical part of the sporangial 

 stalk; zoospores spherical, 3 \x in diameter, with an eccentric colorless 

 globule and long flagellum, emerging through a wide apical or slightly 

 subapical pore formed upon the dehiscence of a circular, 6.5-10.5 \x 

 in diameter operculum which usually remains adherent to the spo- 

 rangium; resting spore not observed. 



Parasitic on Surirella ovata, Austria. 



From the figures given of empty sporangia the wall of the operculum 

 is much thinner than that of the sporangium proper. 



Chytridium versatile Scherffel 



Arch. Protistenk., 54: 177, pi. 9. figs. 17-20. 1926 



(Fig. 31 E, p. 496; also, Fig. 10 M, p. 108) 



Chytridium versatile var. acaulis Canter, Trans. Brit. Mycol. Soc, 31 : 102. 

 figs. 6-7, pi. 10, figs. 7-8. 1947. 



Sporangium narrowly to broadly obpyriform, tapering proximally 

 to a knoblike or slightly prolonged base 3-5 \x in diameter, resting on 

 a short (3.5 \x) slender flexible extramatrical stalk, wall smooth, color- 

 less, thin or somewhat thickened, variable in size, large specimens up 

 to 15-25 \x in diameter by 30-40 \x high, smaller ones 5 by 8 \x\ rhizoids 

 extremely delicate, branched, arising from the endobiotic tip of the 

 stalk; zoospores spherical, 3-5 \x in diameter, with a relatively large 

 colorless centric globule and a long flagellum, emerging upon the 

 dehiscence of an apical convex smooth operculum 8-10 \x in diameter 

 and forming a temporary motionless group surrounded by an evanescent 

 vesicle or "slime" ; resting spore not observed. 



