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



red, oblong, round or angular. Cells 3.5-4 /* diameter 5 often 

 twice as long. 



The only locality in which we found, or know this plant 

 to have been found in fresh-water is the bed of the Susque- 

 hanna River at Harrisburg, Pennsylvania. 



Syn. H. fluviatiliSj Breb. 5 Erythroclathous rivularis, Liebm. ; H. 

 rosea var. fluwaMis, Kg. 



Plate LXIX, fig. 17, thallus peeled from a stone, highly 

 magnified/ Fig. 18, small transverse section, showing the 

 spore receptacles. 



HlLDEBRANDTIA ROSEA, Kg. 



A marine plant common on stones along the New England 

 coast, differs mainly in smaller size, and spherical form of 

 the cells. 



Genus 8, COMPSOPOGON, Mont. 



Thallus filiform, terete, branched, articulate, cells more or less 

 inflated, or slightly constricted at the joints ; filaments corti- 

 cate, somewhat parenchyniatous. Spores, according to Mon- 

 tague, contained in small verrucse in the cortical. 



COMPSOPOGON COERULEUS, Mont. 



Tufts loose, 2-6 inches long, dark, olive-green ; filaments 

 stout and firm, much branched, branches erect patent, 

 mostly alternate, decompound, stems and branches tapering. 

 Diameter of lower part of stems often 250 yw, branches 100 // 

 more or less, tapering to an obtuse point. Articulations of 

 stems and of branches rarely more than half as long as 

 wide ; of the thicker parts only about one-third as long. 

 Older parts of stem corticate, primarily indicated by longi- 

 tudinal threads over the articulations, then by an irregular 

 and thicker reticulation. 



Plate LXX, fig. 1, natural size of plant, figs. 2, 3, younger 

 part, and end of branched filament largely magnified. Figs. 

 4, 5, two short sections of older parts of filaments, showing 

 the cortical, all magnified 125 diameters. 



Collected in fresh-water marsh pool about two miles inland 

 from Green Cove Spring, Florida, March, 1885. About a 

 month later Rev. H. D. Kitchel found the same plant fre- 

 quent at Blue Springs, on the St. John's River. In a collec- 

 tion made by Captain J. Donnell Smith, 1878, we recognized 

 the same form but did not identify it until the gathering of 

 fresh specimens. 



