194 NEMATOPHYCE. 
Ulva pisiformis, Huds. Fl. Ang. 572. With Arr., iv. 120. 
Chetophora elegans, Lyngb. Hydro. t. 65. 
On submerged plants. 
Plate LXXVII. fig. 1. Plants of Chetophora pisiformis, natural 
size, and filaments X 400. ‘ 
Chetophora tuberculosa. (Roth.) Ag. Syst. 
Thallus subglobose, the size of a cherry, bright or pale green, 
surface tuberculose, elastic, fascicles of branches very dense, 
lower articulations cylindrical, the upper swollen, extremities 
cuspidate, sharp pointed, rarely hair-like. 
Size. Cells -009='012 mm., of branches -008-*01 mm. 
Harv. Man. p. 122. Hass. Alg. 126, t. 9, f. 7,8. Kutz. 
Tab. Phye. iii., t.19,f1. Rabh, Alg. Eur. iii, 383. Eng. 
Fl. v., 389. Jenner Tunb. Wells p. 178. Eng. Bot. ii., t. 
2547. Johnst. Fl. Berw. ii., 260. Mack. Hib. 228. Hook. 
Scot. ii, 76. Kirch. Alg. Schles. p. 69. 
Rivularia tuberculosa, Eng. Bot. i., 2366. 
In clear water. 
Plate LXXVTIIT, fig. 1. a, plant of Chetophora tuberculosa, natural 
size. 4, filaments of same X 400 diam. 
Chetophora elegans. (Roth.) 4g. Syst. 
Thallus the size of a pea or a cherry, pale green, surface 
even, elastic, soft, now and then becoming hard, fascicles of 
branches lax, rather flaccid, extremities shortly cuspidate, often 
terminating in a hair. 
Size. Cells :007--009 mm., of branches -005-'007 mm. 
Kutz. Tab. Phye. iii., t. 20, f.1. Rabh. Alg. Eur, iii, 384. 
Kirch. Alg. Schl. p. 69. Eng. Fl. v., 389. Jenner Tunb. 
Wells 178. Mack. Hib. 223, Harv. Man. 122. Grev. Fl. 
Ed. p. 821. Hass. Alg. 127,t. 9, f. 3, 4. 
Rivularia elegans, Eng. Bot. i., t. 1797. Purton Mid. Fl. 
ii, 618. 
In clear water, attached to submerged plants. 
Paler in colour, and more hyaline and gelatinous than C. pisiformis. 
Plate LXXVII. fig. 2. u, plants of Chetophora elegans natural 
size. b,zoogonidia, c, filament X 400. 
Chetophora endivefolia, Ag. Syst. p. 28. 
Thallus linear, flattened, 4-1 inch, now and then elongated, 
bright or dark green, dichotomously laciniate (sometimes with 
the habit of Riccia fluitans), threads and primary branches 
mostly colourless, here and there with green zones, parallel ; 
