THE GREEN ALGAE OF NORTH AMERICA 323 



longations for the purpose of attachment ; frond always at- 

 tached, or loosening and continuing in a free state ; membrane 

 thick, firm, usually distinctly lamellate ; asexual reproduction 

 by 4-ciliate zoospores, produced in little changed cells ; sexual 

 reproduction by biciliate gametes. Marine, rarely fresh water. 



KEY TO THE SPECIES OF CHAETOMORPHA. 



i. Filaments 400-600 fj. diam. 2. 



i. Filaments less than 400 yU. diam. 4. 



2. Filaments increasing noticeably in diameter from the base up. 



i. C. clavata. 

 2. Filaments of nearly uniform diameter except at the extreme base. 



3- 

 3. Basal cell many times as long as any other ; a southern species. 



3. C. antennina. 

 3. Basal cell only slightly longer than the others ; a northern species. 



2. C. melagonium. 



4. Filaments over 40 /u diam. 5. 



4. Filaments not over 40 /j. diam. 7. 



5. Cells 3-8 diam. long. 6. C. cannabina. 



5. Cells not over 2 diam. long. 6. 



6. Filaments 125-400, usually 200-250 AC diam., yellowish-green. 



4. C, aerea. 

 6. Filaments 125-175 /J. diam., dark green ; a southern species. 



5. C. brachygona. 



7. Filaments attached by a small disk ; marine. 7. C, calif arnica. 

 .7. Filaments attached by coralloid, pluricellular branches; fresh water. 



8. C. chelonum. 



1. C. CLAVATA (Ag.) Kiitzing, 1847, p. 166 ; Vickers, 1908, 

 p. 17, PI. VII; P. B.-A., No. 371. Filaments erect, stiff, up 

 to 60 cm. long, base 500-750 //, diam., gradually increasing to 

 1.5 mm. or more at the tip ; lower articulations 3-4 diam. long, 

 those of the upper part about as long as broad, more or less 

 moniliform, color deep green. 



Yar. TORTA Farlow, P. B.-A., No. 571. Fronds loose and 

 curled, cells less moniliform than in the type, and not increas- 

 ing in diameter upwards so noticeably. 



A tropical and subtropical species, found in W. I. and in 

 southern California. In the latter region it occurs mostly as 

 the variety, corresponding to the floating forms of other species 

 of the genus. 



2. C. MELAGONIUM (Web. and Mohr) Kiitzing, 1845, p. 204 ; 

 Harvey, 1858, p. 85; Farlow, 1881, p. 46; P. B.-A., No. 412 

 (forma typica) ; No. 413 (forma ntpincola) ; Conferva melagonium 



