822 AQUATIC PHYCOMYCETES 



tube through which the contents pass (Fig. 62 C, p. 821). The sub- 

 sequent sequence of development is similar to that in Eurychasma, save 

 that the whole body of the fungus with the exception of the tips of the 

 discharge tubes remains endobiotic (Fig. 62 A-G). Further, the zoo- 

 spores of Eurychasmidium encyst outside the sporangium (Fig. 62 H). 

 There is also a marked tendency for infected swollen regions of the 

 algal frond to produce adventitious lateral branches. 



Eurychasmidium tumefaciens (Magnus) Sparrow 

 Biol. Bulletin, 70: 241, text figs. 14-21, pi. 1, fig.l. 1936 



Chytridium tumefaciens Magnus, Sitzungsber. Gesell. Naturforsch. Freunde 



Berlin, 1872: 87; Wissensch. Meeresunters. Abt. Kiel, 2-3: 76, pi. 1, figs. 



1-16. 1875. 

 Olpidium tumefaciens (Magnus) Wright, Trans. R. Irish Acad. Dublin (Sci.), 



26:360. 1879. 

 Pleotrachelus tumefaciens (Magnus) H. E. Petersen, Oversigt Kgl. Danske 



Vidensk. Selskabs. Forhandl., 1905(5): 456. 



Sporangia spherical and 100-1 10 \i in diameter or irregular, lobed, 

 and 110 fi. wide by 200 \x long, from one to six, nearly or completely 

 filling the abnormally enlarged host cell, the alga being stimulated to 

 form clusters of lateral branches in the infected region, wall thin, smooth, 

 colorless; zoospores very numerous, escaping through as many as thirty 

 short narrowly cylindrical sessile discharge tubes, encysting outside, the 

 loosely disposed cysts angular and 4 u. in greatest width, emerging from 

 the cysts after a period of quiescence as ellipsoidal biflagellate zoospores 

 5 u, long by 3 [jl in diameter; resting spore not observed. 



Parasitic in Ceramium flabelligerum, C. acanthonotum, Magnus (loc. 

 cit.), Scotland; Ceramium spiniferum, coll. Cramer, Magnus (loc. cit.), 

 Italy; Ceramium acanthonotum, Wright (1879a: 360), Ireland; "Flor- 

 idees," coll. Massart, de Wildeman (1900b: 4), France; Ceramium 

 rubrum, H. E. Petersen (1905:456), Denmark; Ceramium diaphanum, 

 coll. C. Jao and Sparrow, Sparrow (1936b: 241, figs. 14-21, pi. 1, fig. 

 1), United States. 



The American material was found only in the nodal cells of the alga. 

 The earliest developmental stages observed showed an already well- 

 established spherical thallus easily distinguishable from the host con- 



