424 BULLETIN OF THE BUREAU OF FISHERIES. 



Family 1. CLADOPHORACE^E (Hassall) De Toni. 



Frond of simple or branching, monosiphonous filaments, free or more or less united 

 laterally; cells multinucleate, rarely uninucleate, with chromatophore net form, or 

 broken into many small portions, with many pyrenoids; asexual propagation by four 

 ciliate zoospores (sometimes by biciliate?) and by akinetes; sexual reproduction by 

 biciliate, usually similar gametes. Zoospores and gametes formed in little changed 

 vegetative cells. 



About 350 species, marine and fresh water, throughout the world. 



KEY TO GENERA. 



a. Filaments simple, firm b. 



b. Filaments regularly cylindrical or clavate , i. Chaetomorpha (p. 424). 



bb. Filaments usually more or less irregular 2. Rhizoclonium (p. 427). 



00. Filaments branched c. 



c. Branches usually short, rhizoidal 2. Rhizoclonium (p. 427). 



cc. Branches of successive orders, but of the same character 3. Cladophora (p. 427). 



Genus i. Chaetomorpha Kuetzing. 

 Chaetomorpha, Kuetzing, 18453, p. 203. 



Frond />f a single unbranched series of multinucleate cells, all but the usually longer 

 basal cell capable of division; basal cell producing either a disk or more or less branched 

 rhizoidal prolongations serving for attachment; frond always attached, or becoming 

 loose and continuing in a free state; membrane thick, firm, usually distinctly lamellate; 

 asexual propagation by four-ciliate zoospores, produced in little changed cells; sexual 

 reproduction by similar biciliate gametes; akinetes sometimes formed (?). 



About 50 species, mostly marine, rarely in fresh water, throughout the world from 

 Arctic to Antarctic regions. 



KEY TO SPECIES. 



Filaments usually 400 to 500 mic. diameter, sometimes less, Beaufort material 120 to 240 

 mic. ; coarse, wiry. .'. i. C. melagonium (p. 424). 



Filaments 125 to 400 mic. diameter, sometimes less, usually 200 to 250 mic. , Beaufort material 

 80 to no mic.; yellowish green, soft, flaccid._. 2. C. linum (p. 425). 



Filaments 125 to 175 mic. diameter, Beaufort material 100 to 175 mic. ; dark green, soft, flaccid 



3. C. brachygona (p. 426). 



1. Chaetomorpha melagonium (Weber and Mohr) Kuetzing. Fig. 2C. 



* Conferva melagonium, Weber and Mohr, 1804, p. 194, pi. 3, f. a. 

 Chcetomorpha melagonium, Kuetzing, 18453, p. 204. 

 Chatomorpha melagonium, Harvey, 1838, p. 85. 

 Cfuetomorpha melagonium, Farlow, 1882, p. 46. 

 Chtzlomorpha melagonium, De Toni, 1889, p. 273. 

 Chtetomorplui melagonium,, Collins, 1909, p. 323. 

 P. B.-A. No. 412 (forma typica). No. 413 (forma rupincola). 



Filaments erect, coarse and wiry, dark glaucous greenf usually 400 to 500 mic. diameter; sometimes 

 300 mic. or less; cells i to 2 diameters long. 



Common from New Jersey to Greenland; Alaska; northern Europe. 



Abundant on rocks Shackleford jetty, Beaufort, N. C., forming dense masses with Ufaa lactuca, 

 Enteromorpha prolifera, and E. lima, about low-water level, May, 1907. 



Two forms of the species are recognized: f. rupincola (Areschoug) Kjellman, growing attached and 

 erect, usually quite straight; and f. typica Kjellman, unattached, lying loose in crisped, tangled masses. 

 The latter form is apparently only a later stage of the plant. There is considerable variation in the size 

 of the filaments, and the slender forms, sometimes as low as 300 mic. diameter or less, are not always easy 

 to distinguish from C. linum; but the greater rigidity and the dark, glaucous, green color are usually 

 sufficient marks. 



