CHYTRIDIALES 517 



Chytridium stellatum (H. E. Petersen) Koch 



J. Elisha Mitchell Sci. Soc, 67: 272, pi. 21, figs. 28-41. 1951 



Phlyctochytrium stellatum H. E. Petersen, Bot. Tidsskrift, 29:417. 1909; 

 Ann. Mycologici, 8: 550, fig. xxiii. 1910. 



"Sporangium extramatrical; sessile; procumbent, resting on the host 

 wall; main body of sporangium thin-walled, arising as a lateral out- 

 growth from the basal part of the encysted and germinated zoospore, 

 which becomes displaced laterally and is part of the sporangium; thin- 

 walled part subspherical, elliptical, ovoid or somewhat irregular, 5.1- 

 44.0 \i long 4.4-26.4 u, wide; wall colorless, smooth, thin and delicate, 

 collapsing after discharge of zoospores, except for persistent, thick- 

 walled cyst; exit papilla, when discernible, broadly convex, variously 

 located. Zoospores spherical, 4.2-5.5 \x in diameter with an eccentric, 

 colorless, highly refractive globule, 2.2-3.3 \x in diameter, and a flagellum 

 about five times as long as the diameter of the spore body; emerging 

 through an orifice after the detachment of an operculum, about 5 u. in 

 diameter, and forming a more or less globular mass, with individual 

 zoospores distinct but adpressed, and lying quiescent for about one 

 minute, while slightly parting and extending their flagella, and then 

 rapidly dispersing, the swimming spore with a posteriorly attached and 

 directed flagellum. Apophysis intramatrical, spherical, 6.0-15.4 \i in 

 diameter, or slightly fusiform, wall holding shape after discharge of 

 sporangium, connected to extramatrical, encysted zoospore by old germ 

 tube, 0.5-1.5 \x in diameter; rhizoidal system coming out from base of 

 apophysis, extensively branched, rhizoids 0.2-1.5 jjl in diameter, with 

 blunt tips, sometimes becoming extramatrical. Resting body apparently 

 formed asexually, in intramatrical swelling; spherical, 11.0-26.4 ;x in 

 diameter with protoplast 8.8-14.3 u. wide, or subspherical; wall two- 

 layered, hyaline, glistening, outer layer with numerous, prominent 

 excrescences up to 6 u, long, straight or bent, pointed, blunt or regularly 

 to irregularly clavate; with a large, eccentric, colorless, highly refractive 

 globule surrounded by many much smaller ones; empty, extramatrical 

 cyst remaining expanded or all but basal portion soon collapsing; 

 germination not observed 1 ' (Koch, he. cit.). 

 In Spirogyra sp., Petersen (be. cit.), Denmark; Zvj^/w/s/?.,ScherfTel 



