CHYTRIDIALES 513 



Chytridium sexuale Koch 

 J. Elisha Mitchell Sci. Soc, 67: 267, pi. 19, figs. 1-9; pi. 20, figs. 10-27. 1951 



"Sporangium, usually on an inconspicuous stalk up to 2.2 (j. long, 

 arising as an outgrowth of the distal end of the germinated zoospore, 

 which is 2.5-4.0 \x wide and is the basal part of the sporangium; rarely 

 perpendicular to the host wall and with radial symmetry, but usually 

 somewhat inclined and bent slightly or through nearly a 180° angle and 

 bilaterally symmetrical; rarely twisted or helicoidal; essentially obpyri- 

 form or spatulate and usually with a slight bulge in all directions between 

 the zoospore and broadest part, and gibbous distally when bent over; 

 12-43 \x long x 6-21 jjl wide (mostly 30-40 14-19 [j.); wall colorless, 

 smooth, remaining intact after discharge of zoospores ; detached oper- 

 culum 4.9-1 5.6 [x in diameter (mostly 1 1.0-12.5 u.). Motile cells spherical, 

 3.2 4.5 \x in diameter, with an eccentric, colorless, highly refractive 

 globule 1 .2-1 .6 [x in diameter, and a flagellum about 1 7 \x long; emerging 

 fully cleaved, separate and spherical, through a terminal, circular orifice 

 when the operculum is completely detached, or through a slit when the 

 operculum is only partly detached, lying quiescent for about one minute 

 in a loose cluster while unwrapping their flagella, and then rapidly 

 dispersing, some of them remaining within the sporangium and emerging 

 one to a few at a time; swimming cell with a posteriorly attached and 

 directed flagellum. Penetration tube of the encysted motile cell when 

 passing through the host wall is 0.7-1.3 \x wide, reduced abruptly to 

 0.3-0.9 \x in width within the host protoplasm; distal end swelling to 

 form the spherical apophysis, 3.2-9.2 \x in diameter (mostly 6.5-8.0 \x) 

 with a smooth wall; no rhizoidal system. Resting body essentially spher- 

 ical, 11.3-14.0 [x in diameter, protoplast 9.5-12.0 \x wide with a large, 

 eccentric, colorless, highly refractive globule surrounded by many much 

 smaller ones, and a wall 0.6-1.1 \x thick, including the covering of 

 numerous, short, blunt warts; sexually formed; female thallus indistin- 

 guishable from young sporangial thallus, the epibiotic part 4.3-7.8 \x 

 high, with the cyst portion inconspicuously to considerably expanded 

 distally; contents of the encysted male cell, which is 3.2-3.9 \x in diam- 

 eter, passing through a germ tube into the epibiotic, expanded part of 

 the female thallus; the fusion protoplasm moving into the endobiotic, 



