116 FRESH-WATER ALG^E OF THE UNITED STATES. 



Propagation by zoospores, which develop in the cells of the 

 upper branches. 



CHAETOPHORA PISIFORMIS, (Both.) Ag. 



Thallus globose, smooth, about the size of a pea, often 

 smaller, and sometimes as large as a cherry ; bright green, 

 shining ; frequently aggregated, not rarely confluent ; fila- 

 ments much branched, radiating ; articulations cylindrical ; 

 terminal cells awl-shaped, not rarely ending in a chaeta. 



Diameter of filaments, 6-9 yu; 1-2* times longer. 

 Diameter of branchlets, 6 yw; 11-3 times longer. 



Syn. Ulva pisiformiSj Huds., Chaetophora elegans, Lyngb. 

 On submerged plants and stones. 



Plate CIII, figs. 1, 2, 3, as frequently seen attached to 

 grasses ; figs. 12-15. surfaces of river stones frequently 

 covered ; thalli primarily very small, then enlarging, and 

 often confluent. 



CHAETOPHORA ELEGANS, Ag. 



Thallus smooth, elastic, soft, rarely becoming hard ; size of 

 a pea or cherry ; fascicles of branches lax, rather flaccid, ex- 

 tremities shortly cuspidate, usually terminating in a bristle. 



Filaments 9-12 /* in diameter ; Is -3 times as long. 

 Branches, 7-10 n in diameter ; 1-1* times as long. 



Syn. Rivularia elegam, Eng. Bot. 



Attached to submerged grasses, leaves, etc. 



Plate CIII, fig. 7, thalli on a submerged fallen leaf; figs. 

 4, 5, a part of a larger and a smaller thallus magnified about 

 250 diameters ; fig. 6, a branch producing zoospores ; figs. 

 8-10, three branches developing long filaments. For full 

 development see Plate C, fig. 1. 



Compare note under Stigeodonium fastigiatum, Kg. 



CHAETOPHORA TUBERCULOSA, (Roth.) Ag. 



Thallus subglobose, the size of a cherry or larger, usually 

 rather dull green, surface tuberculose, elastic ; fascicles of 

 branches very dense, lower articulations cylindrical, the 

 upper swollen, extremities cuspidate, sharp pointed, rarely 

 hair-like. 



Diameter 9-12 // ; branchlets slightly thinner. 



Syn. Eivularia tuberculosa, Eng. Bot. 

 In clear, usually, spring water. 



