CHYTRIDIALES 259 



Rhizophydium fragilariae Canter 



Ann. Bot. London (N.S.), 14: 275, fig. 9. 1950 



(Fig. 10 A, p. 108) 



Sporangia epibiotic, spherical to subspherica!, 3-10 \i in diameter, 

 containing three to twenty zoospores; sporangium wall deliquescing 

 at maturity, forming one to three openings through which the zoo- 

 spores emerge; zoospore spherical, 2-2.4 fx, with a conspicuous ante- 

 rior globule and single posterior flagellum; endobiotic rhizoid a short 

 unbranched or once-branched thread; resting spore not observed. 



Parasitic on the planktonic diatom Fragilaria crotonensis, Great 

 Britain. 



Although Canter's form is said to be confined to this species of 

 Fragilaria, the fungus figured by Huber-Pestalozzi (1946:95, fig. 5e) 

 on Fragilaria capucina from Swiss plankton may possibly belong here. 



See remarks under Rhizophydium achnanthis, above. 



Rhizophydium macrosporum Karling 

 Bull. Torrey Bot. Club, 65: 439, pi. 20, figs. 1-17.J938 



"Thalli eucarpic, numerous, gregarious. Zoosporangia hyaline, 

 smooth, predominately spherical 22-1 10 [x, oval, broadly pyriform, 

 and urceolate with 1 to 5, usually 2 or 3, low inconspicuous exit pa- 

 pillae. Zoospores spherical 4.5-6 \x, hyaline, with an unusually large, 

 3-4 [i. clear refractive globule and a 25-35 jx long cilium; occasionally 

 becoming amoeboid; initial swarmspores emerging in a small glob- 

 ular mass surrounded by a hyaline matrix and lying quiescent for 

 a few moments before separating; the remainder becoming active within 

 the sporangium and emerging usually one by one. Rhizoidal system 

 usually extensively developed, coarse, and branched, main axis oc- 

 casionally 6 \x in diameter; delimited from the sporangia by a cross 

 wall at maturity; arising from a single point or rarely from several 

 places at the base of the sporangium. Resting spores hyaline, smooth, 

 spherical, 15-30[j., oval, 18 x 20-33 x 36 \x, or slightly irregular with 

 a wall 1.5-2 [j. thick, and one or more large refractive globules; ger- 

 mination unknown" (Karling, he. cit.). 



On cooked ground beef, dead cells of Cladophora glomerata, Pithoph- 



