326 FRESH-WATER ALG.E OF THE UNITED STATES. 



SYNECHOCOCCUS AERUGINOSUS, Naeg. 



Cells 13-2 times as long as broad, solitary or two joined 

 end to end ; cytioptesm aeruginous. 



Diameter of cells, 7-16 /^. 



On wet rocks. 

 Plate CCX, fig. 11, a number of cells variable in size. 



Genus 111, MERISMOPEDIA, Meyen. 



Cells globose, or at the time of division oblong, 4, 8, 16, 32, 

 64, or 128 associated in tabular families of a single stratum, 

 forming a quadrate, plane, free swimming thallus. 



MERISMOPEDIA GLAIK I A, Naeg. 



Thallus more or less limited, light aeruginous or some- 

 times glaucous green. Cells globose, or more or less oval or 

 oblong as they approach division. Thallus composed of 

 4-64 cells, rarely more. 



Diameter of cells, 3-5 /j. 



Syn. Gonium glaucum, Ehrb. ; Mer. nova, Wood. 

 Not infrequent in ponds or sluggish waters. 



Plate CCX, figs. 12-15, various sizes of cells, not different 

 species, but conditions of the same plant. 



MERISMOPEDIA CONVOLUTA, Breb. 



Thallus membranous, visible to the unaided eye, more or 

 less folded or convolute ; families often composed of 256 

 geminate cells, arranged in subfamilies, sometimes two of 

 these families conjoined with a composite family ; cells 

 spherical or oblong. Cytioplasm homogeneous, bluish green. 



Diameter of cells, 4-4.5 ^. 



Shallow pools, forming a distinct layer upon the muddy 

 bottom, or separating and then floating on the surface. 



Plate CCX, fig. 14. may represent a small family of 64 

 cells. A thallus often contains hundreds of these. 



European works describe numerous species separated by 

 no more distinctive features than sizes of cells, and of fami- 

 lies, or color of cytioplasm, as molacea, aeruginea, and 

 ochracea, all of which appear to represent mere conditions 

 of the same plant. 



