572 AQUATIC PHYCOMYCETES 



emerging from the base of the sporangium, strongly developed, much 

 branched, polyphagous, the tips at times becoming extramatrical; zoo- 

 spores spherical, 5-7.5 u. in diameter, posteriorly uniflagellate, with a 

 colorless centric or eccentric oil drop 1.2-2.5 \i in diameter in the gran- 

 ular vacuolate plasma, escaping upon the dehiscence of a circular oper- 

 culum which terminates the discharge tube and remaining in a motion- 

 less group before the orifice, the group slowly moving away and losing 

 coherency and the individuals assuming motion; resting spore endo- 

 biotic, nearly spherical, brown, thick-walled, the outer surface provided 

 with irregularly disposed thick slightly reflexed scales, contents bearing 

 a large eccentric oil drop 1 1 u, in diameter, formed asexually and endog- 

 enously in a sporangium-like structure which it partly or completely 

 fills and, like the sporangium, bearing extramatrically the persistent 

 cyst of the infecting zoospore, germination not observed. 



Saprophytic in Spirogyra, Zygnema, Hungary. 



The presence of an operculum distinguishes this as a species of 

 Endochytrium rather than of Entophlyctis. 



Endochytrium digitatum Karling 



Mycologia, 30: 307, text figs. 20-37. 1938 



"Thalli numerous, intramatrical, monocentric, eucarpic. Zoospo- 

 rangia hyaline and smooth except for one to several blunt digitations 

 at or near the base; formed as an enlargement on the germ tube and 

 delimited from the rhizoidal system by a cross wall at maturity; elongate 

 and obclavate 11 :■; 44 u. — 18 x 35 u., pyriform, 15 x 22 u, — 71 x 120 u,, 

 obpyriform, irregular, subspherical, somewhat triangular and lobed, 

 with 1-4, usually one, single or branched, straight, curved, undulating, 

 or coiled, tapering exit tubes, 5-18 u. in diameter and 10-275 \x in length, 

 which may occasionally extend 88 \i beyond the surface of the host wall. 

 Operculum spherical or slightly oval, 3.3-5.5 u.. Zoospores hyaline with 

 a clear refractive globule 1.6-2.2 \i in diameter, spherical, 4.4-5.5 u,, 

 posteriorly uniciliate; emerging fully formed and singly, and lying 

 quiescent in a globular mass a short while before becoming actively 

 motile, intermittently amoeboid. Rhizoidal system well developed and 

 richly branched, extending sometimes for a distance of 550 jjl, smooth 



