162 AQUATIC PHYCOMYCETES 



tetraspores of Polysiphonia violacea and (2) those in parietal cells of 

 the cystocarp of P. elongata. 



1. Sporangia formed in tetraspores of Polysiphonia violacea and 

 assuming their shape: Sporangia with smooth colorless walls which 

 stain violet with chloriodide of zinc, with one or more (usually two 

 or three) somewhat prolonged discharge tubes, 30-45 by 39-60 [i, of 

 variable shape (if occurring in the tetrasporangium before formation 

 of the tetraspores, somewhat regularly spherical and filling it or, in 

 instances of multiple infection, spherical and grouped; if formed during 

 division of the tetrasporangium into tetraspores, filling the two-celled 

 or each of the four-celled [tetrasporic] structures); zoospores after 

 formation moving within the sporangium and escaping individually, 

 body ellipsoidal, 2-3 [x in diameter, flagellation unknown; other char- 

 acters unknown. 



2. Sporangia parasitic in parietal cells of the cystocarp of Poly- 

 siphonia elongata: Sporangia of irregular rounded form, with a smooth 

 wall, oily reiringent contents, and from one to three discharge tubes; 

 large specimens 40 by 41 u., discharge tube 22 [x; medium-sized ones 

 10 by 29 [jl. 



In Polysiphonia. Dhnmark. 



The lobations on sporangia formed in the dyads of the tetraspo- 

 rangia (Petersen, op.cit., fig. IV, 1) indicate a relationship of these 

 forms to Petersenia, where, if the zoospores are found to be biflagellate, 

 they should be placed. 



Other imperfectly known types in marine algae are described by 

 Petersen (op. cit., p. 464). 



? Pleotrachelus minutes H. E. Petersen 



Oversigt. Kgl. Danske Vidensk. Selskabs. Forhandl., 1905 (5): 451, 



fig. II. 1-4 



Sporangium of variable shape, spherical or elongate-cylindrical, 

 with a smooth thin wall, largest 16-24 by 12-16 \x, with from one to 

 three discharge tubes 4 [i long; host cell little hypertrophied. 



In hairs o\' Chorda filum, Petersen (be. cit.), Denmark; Chorda 

 filum, Aleem (1953:7, figs. 7-8), Sweden; Litosiphon pusillus, J. 

 I eldmann (1954: 132), Fram i. 



