270 AQUA TIC PH YCO M YCETES 



cies might more suitably be called "Chytridium vagans" rather than 

 "C pollinis-pini" The fungus on pine pollen in France which Cornu 

 (1872a: 121) referred to R. pollinis-pini had endobiotic resting spores. 

 These spores have been thought by Fischer (1892:89) to belong to 

 one of several endobiotic Phycomycetes which also inhabit pollen 

 grains. Schcnk's fungus (1858b: 8) on Chlamydomonas sp. is probably 

 R. globosum. The chytrid briefly described by Serbinow (1907: 156) 

 as a facultative parasite of coniferous pollen grains was shown, when 

 the rhizoids were stained, to be a species of Phlyctidium rather than 

 of Rhizophydium (see, however, Couch's [1932] observations on the 

 rhizoids and see Phlyctidium pollinis-pini below). 



Species of Rhizophydium which attack the germinating oospores of 

 various members of the Peronosporaceae have been assigned to R. 

 pollinis-pini by Schroeter (1879: 84) and by Melhus (1914: 55, pi. 4). 

 De Bary (1863: 21) also mentioned a "Chytridium''' parasitic on ger- 

 minating oospores of Albugo. It is evident from the description and 

 figures of the fungus studied by Melhus that his material was not 

 R. pollinis-pini. If the flagellation of the zoospores has been correctly 

 interpreted, it may be a species of Rhizidiomyces. Whether the other 

 forms inhabiting peronosporaceous oospores are identical with Melhus' 

 fungus cannot be ascertained. The latter may be described as follows: 



Sporangium obpyriform or ovoid, up to 40 jj. in diameter, often 

 narrowing at the base to form a short stalk, wall fairly thick, color- 

 less, with a single apical or lateral papilla (occasionally two) 3-5 fi. 

 in diameter; rhizoids fairly coarse, branched, arising from a central 

 axis which is cylindrical or, sometimes, irregularly inflated; zoospores 

 spherical or pyriform, 3 u, in diameter, with a slightly eccentric color- 

 less globule and an anterior flagellum 12 [x in length, escaping indi- 

 vidually and fully formed through an apical or lateral pore (occa- 

 sionally two); resting spore (?) with a thick smooth yellow-brown 

 wall, formed "inside the old sporangium," germination not observed. 



? Phlyctidium pollinis-pini (Braun) Schroeter 



Kryptogamenfl. Schlesien, 3 (1): 190. 1885. Non Sorokin, Arch. Bot. Nord 



France, 2: 19. 1883 (separate) 



