THE GREEN ALGAE OF NORTH AMERICA 339 



1846-51, PL CCXCVIII ; C. fracta forma flavescens Collins, 

 1902, p. 124; P. B.-A., Nos. 1077, 1229. Filaments at first 

 attached, later loose floating, 30-60 /j. diam., forking at wide 

 angles, cells 6-10 diam. long; ramuli not much smaller, taper- 

 ing but with blunt tips ; forming dense yellowish-green floating 

 masses in high, warm pools. Mass, to N. Y. Europe, 



This form occurs in high rock pools, where the water is quite 

 salt; it has generally been considered a form of C. fracta, but 

 is a smaller plant, attached in early stages, and inhabits strictly 

 salt water. 



12. C. CONSTRICTA Collins, 1909, p. 19, PL L,XXVIII, figs. 

 4and5. Tuftsdense, up 10 cm. high, somewhat fastigiate ; main 

 filaments up to 65 fj- diam., branches smaller, ultimate ramuli 

 about 25 /j. diam.; cells 5-20 diam. long, mostly somewhat 

 clavate, often with a distinct annular constriction about one 

 diameter above the lower end. Branching mostly opposite be- 

 low and often above, but also often lateral, the short ramuli some- 

 what secund ; branches at first rather patent but soon curving 

 upward ; apex of terminal cell shortly conical with rounded tip. 



In general appearance not unlike a small and dense form of 

 C. gracilis such as is often seen in shallow pools on the north At- 

 lantic coast, but the resemblance is merely external, the branch- 

 ing being more like that of C. rupestris. The cells vary much 

 in length, but average quite long and usually increase slightly 

 in diameter from base to summit. In the older parts the 

 branching is quite regularly opposite or apparently trichoto- 

 mous. The branching is quite dense, the outline usually reg- 

 ular. The constriction does not occur on all the cells, but is 

 often very distinct, the diameter of the cell being reduced at this 

 point to less than half the normal, the interior thickening of the 

 cell walls contributing to this reduction ; a slight manifestation 

 of a character that is quite important in some Valoniaceae. 



13. C. CRISPULA Vickers, 1905, p. 56 ; 1908, p. 19, PL 

 XVI. Forming dark green spongy masses of contorted fila- 

 ments, 45-50 /x diam., twisted in rope-like tufts; branches 

 alternate or opposite, near the tips somewhat secund, curved ; 

 cells about 8 diam. long. Barbados. 



Resembling in habit a Chaetomorpha , but with genuine 

 branching. 



14. C. FLEXUOSA (Griff.) Harvey, 1846-51, PL CCCLJII; 

 1858, p. 78; Farlow, iSSi, p. 54; P. B.-A., Nos. 1076, 1527. 



