THE GREEN ALGAE OF NORTH AMERICA 297 



XXXVIII, figs. 2 and 3 ; P. B.A., 1330 ; C. endivaefolia Harvey, 

 1858, p. 69 ; Wolle, 1887, p. 117, PI. CIV ; C. cornu-da-mac P. 

 B.-A., No. 68. Thalli irregularly extended, lobed, laciniate, or 

 branched, main filaments elongate, closely packed in skeins or 

 strands, with alternate or secund branches bearing densely 

 fascicled, usually setiferous ramuli ; cells of main filaments 

 8-16 /A diam., 2-6 diam. long, cylindrical or inflated; ramuli 

 often curved, often torulose, 6-n /u. diam., cells 1-2 diam. long. 

 Generally distributed. Europe, So. America. 



Thoroughly distinct from the three preceding globular 

 species, but varying so much in form and ramification that it 

 has received many specific and varietal names, but no clear lines 

 can be drawn. Much of the variation appears to be due to the 

 rapidity of the water in which it grows ; between the forms with 

 somewhat flattened and lobed thallus, 2-3 cm. long, and the 

 slender, much branched, filamentous forms, several dm. long, 

 every gradation can be found. 



24. STIGEOCLONIUM Kiitzing, 1843, P- 2 53- 

 Frond mucilaginous, composed of a branching filament, with- 

 out much distinction in character between main filaments and 

 branches ; terminal cells pointed or prolonged into a seta ; 

 chromatophore a parietal band, filling the smaller cells, zonate 

 in the larger. Asexual reproduction by 4-ciliate zoospores with 

 a red stigma ; also by akinetes which produce 2-ciliate zo- 

 ospores, by aplanospores, and also by a Palmella stage. Sexual 

 reproduction by conjugation of 2-ciliate gametes with a red 

 stigma. 



A rather large genus of fresh water algae, very well limited 

 but whose species show few sharp dividing lines. 



KEY TO THE SPECIES OF STIGEOCI.ONIUM. 



i. Opposite branching predominant. 2. 



I. Alternate branching predominant. 8. 



2. Filaments 10 /tx diam. or less. 6. 5". tenue. 



2. Filaments 11-30 /u diam. 3. 



3. Lower cells much inflated. 5. S. ventricosum. 



3. Lower cells slightly or not at all inflated. 4. 



4. Lower cells not over 2 diam. long. 5. 



4. Lower cells 2-8 diam. long. 6. 



5. Lower cells seldom as long as broad ; ramuli tapering, thorn-like. 



4. S. subuligerum* 

 5. Lower cells usually longer than broad ; ramuli short- pointed. 



i. S. lubricum. 



