THE GREEN ALGAE OF NORTH AMERICA 281 



The irregularly and densely branched- fronds form an open 

 or almost continuous layer in the membrane, sending short 

 branches up and down, to the outer surface of the membrane, 

 or to the surface of the shell. In England it is generally ac- 

 companied by the other species, T, infricafa Batters, with more 

 cylindrical cells and looser branching ; this species has not yet 

 been noticed in this country. 



4. CHAETOSPHAERIDIUM Klebahn, 1891, p. 7. 

 Frond microscopic, epiphytic on various algae ; cells globose 

 or hemispherical, with disk-shaped chromatophore and one py- 

 renoid, bearing above a very long, delicate sheathed hair ; cells 

 dividing by a horizontal wall, the daughter cell then passing to 

 the side of the mother cell, or emitting a tubular projection, at 

 the end of which is formed a new setiferous cell ; reproduction 

 by motile spores, but character and development unknown. 

 When a setiferous cell has divided and formed a tube, the con- 

 tents of the lower (daughter) cell passes through the tube to the 

 new cell; the tube either disappears as in C. globositw, or re- 

 mains an empty utricle as in C. Pringsheimii. 



KEY TO 'THE SPECIES OF CHAETOSPHAERIDIUM. 

 i. Utricles short and evanescent; general gelatinous envelop present. 



i. C. globosum. 

 i. Utricles well developed ; no general gelatinous envelop. 



2. C. Pringsheimii. 



1. C. GLOBOSUM (Nordst.) Klebahn, 1893, p. 306, PI. XIV, 

 figs. 5-io; Hazen, 1902, p. 229; Aphanochaetc globosa Wolle, 

 1887, p. 119, PI. CV, fig. 5. Cells 12-18 n diam., sheath 16-17 p. 

 long, 2-3 /u. diam. ; cells closely set, utricles inconspicuous, gen- 

 eral gelatinous coating ample. On algae, chiefly Oedogonium. 

 N. H. to N. J., Neb. Europe. 



2. C. PRINGSHEIMII Klebahn, 1891, p. 7; 1892, p. 268,- 

 PL IV. Cells 9-12 p. diam., sheaths 13-18 /* long, about 2 p. 

 diam. ; cells united by well developed, persistent utricles into 

 creeping filaments, sometimes with erect ends ; no general 

 gelatinous coating. On algae, chiefly Colcochactc. Fig. 104. 

 Canada, near Lake Superior. Europe. 



There may be some doubt whether the plant figured by Hazen, 

 1902, PI. XLII, figs. 3 and 4, is really C. Pringsheimii, as 

 stated, or a form of C. globoswn ; a comparison of this plate with 

 Klebahn's plate would seem to indicate that they were not the 

 same species. 



