424 BULLETIN OF THE BUREAU OF FISHERIES. 
Family 1. CLADOPHORACEZ (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. 
G. Filaments simple, £770 ooo o'5 oo o0\s wjahaydie' os eps im ny ie an cee ae STL: ea RS nMOS WLC 8 b. 
b. Filaments regularly cylindrical or clavate......................-. -....1. Chetomorpha (p. 424). 
bb. Filaments usually more or less irregular...........2...02-2ceceeeeeee 2. Rhizoclonium (p. 427). 
Ga, Hilamesits Prat CHed aco oo0 oslo mas as-) cco yeiepeusiecagsinies S, sispaecaceyelics Wacle Gas ecesj-i= EE OE Pee eae Ge 
64 Branches usually, short, shizoidal a, ... thcjrse . «olin 3. cule. 2. elas ineratee ous 2. Rhizoclonium (p. 427). 
cc. Branches of successive orders, but of the same character.................. 3. Cladophora (p. 427). 
Genus 1. Cheetomorpha Kuetzing. 
Chetomorpha, Kuetzing, 1845a, p. 203. 
Frond of 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 
TTC AREOALSORNWARYinn ee Tene ede Sek ee a a emer ee hi as 1. C. melagonium (p. 424). 
Filaments 125 to 400 mic. diameter, sometimes less, usually 200 to 250 mic., Beaufort material 
80to 110 mic.; yellowish green, soft, flaccid. ...............0s0eececeevest sees 2. C. linum (p. 425). 
Filaments 125 to 175 mic. diameter, Beaufort material 100 to 175 mic.; dark green, soft, flaccid 
RSE. AR otell. 3 @ ola bola alm neteralatd «eg Gel OFaChyyoral(p.420): 
1. Cheetomorpha melagonium (Weber and Mohr) Kuetzing. Fig. 2C. 
Conferva melagontum, Weber and Mohr, 1804, p. 194, pl. 3, f. 2. 
Chetomorpha melagonium, Kuetzing, 18454, p. 204. 
Chetomor pha melagonium, Harvey, 1858, p. 85. 
Chaetomorpha melagonium, Farlow, 1882, p. 46. 
Chetomorpha melagonium, De Toni, 1889, p. 273. 
Chetomorpha melagonium, Collins, 1909, p. 323. 
P. B.-A. No. 412 (forma typica), No. 413 (forma rupincola). 
Filaments erect, coarse and wiry, dark glaucous green, usually 400 to 500 mic. diameter; sometimes 
300 mic. or less; cells 1 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 Ulva lactuca, 
Enteromorpha prolifera, and E. linza, 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. 
