THE GREEN ALGAE OF NORTH AMERICA 289 



found in a cell; Huber, 1892, however, considers that the ap- 

 parent separate disks are thickenings in a single parietal 

 coating. 



C. americana (Snow) nov. comb. ; Ulvella americana Snow, 

 1899, p. 309, PI. VII. Disk 1-3 mm. diam. ; marginal cells 

 10-17X5-13 p, squarish or horizontally elongate; central cells 

 10-13 /* diam., vertically elongate, ultimately in several layers; 

 superficial cells sometimes producing evanescent gelatinous 

 hairs; zoospores 4-ciliate, 10-15X8-13^, oval or nearly spheri- 

 cal, with numerous oil globules and large brick-red stigma ; 

 4-8-16 produced in a cell, from which they escape together, 

 surrounded by a common gelatinous envelope ; germinating 

 immediately after coming to rest, and producing a plant like 

 the parent. Fig. 96. Mich. 



The 4-ciliate zoospores with prominent red stigma, issuing 

 from the mother cell in a common envelope, and the gelatinous 

 hairs, all indicate Chactopeltis rather than Ulvella as the proper 

 genus for this plant. Moreover, Ulvella is a strictly marine 

 genus as far as known, and has a structure more parenchym- 

 atous and less gelatinous. 



From C. orbicularis Berthold and C. minor Mobius it would 

 seem to be distinguished by the polystromatic disk. Some 

 peculiar conditions noted by Miss Snow, such as germinating 

 zoospores forming two or four zoospores of a secondary genera- 

 tion ; also the assuming of a sort of Palmella-state, may be due 

 to conditions of cultivation, but at any rate raise interesting 

 questions. 



17. CHAETOBOLUS Rosenvinge, 1893, p. 928. 



Frond epiphytic, hemispherical or more rarely subglobose ; 

 cell division in all directions ; in the hemispherical frond the 

 cells of the basal margin radiately arranged ; superficial cells, 

 except those of the basal margin, and those covered by other 

 algae, produced into long inarticulate setae, continuous with 

 the cells producing them ; reproduction by zoospores produced 

 in the superficial cells ? Marine. 



' Nearly allied to Ochlochaetc, but normally polystromatic, while 

 Ochlochacte is normally monostromatic. Only one species. 



C. GIBBUS Rosenvinge, 1893, p. 928, fig. 41. Frond 100-150 

 H diam., cells of irregular rounded form, up to 30 /* diam., with 

 dense chromatophore ; the free superficial cells with very long, 

 slender setae, 4-5 /u diam. at the base, much more slender near 



