64 FRESH-WATER ALG.E OF THE UNITED STATES. 



disciform thallus ; articles oblong, anteriorly more or less di- 

 lated, often furnished with a long seta on the back or superior 

 angle. 



COLEOCHAETE SOLUTA, Pringsh. 



Forms small discs composed of radiating dichotoniously 

 branched filaments lying closely side by side but not adher- 

 ing, cells one and one-half to three times as long as wide ; . 

 carpogons (oogonia) usually develop near the terminal cells, 

 at first small, flask shaped, but gradually enlarging, be- 

 coming orbicular by a cortical forming around them. 



Vegetative cells average 25 /i diameter. Carpogons fully 

 developed about 200 /* diameter. 



Not rare in ponds ; frequent in New Jersey waters. 



Plate LXXII, figs. 1, 2, parts of fronds ; fig. 3, loose growth 

 in fruit ; figs. 4, 5, two carpogons ; figs. 6, 7, young forms. 



COLEOCHAETE SCUTATA, Breb. 



In manner of growth similar to the preceding, but distinct 

 in having the filaments adhering side by side, forming a kind 

 of irregularly orbicular, parenchymatous disc; cells sub- 

 quadrangular ; oogonia subglobose, near the margins, corti- 

 cated above, naked below. Fronds and cells very variable 

 in size. 



Syn. Phyllactidium setigerum, Kg. 



An aquatic plant, everywhere; much more frequent than 

 C. sohita. 



Plate LXXII, figs. 8-13, young and older plants of several 

 forms. 



COLEOCHAETE ORBICULARIS, Pringsh. 



Like C. scutata in structure and fruit, but always exact 

 orbicular ; the size of the cells is usually smaller. 



The distinction does not seem sufficient for a good species ; 

 probably a mere variety. 



Syn. Phyllactidium pulchellum, Kg. Plate LXXII, fig. 14. 

 Localities similar to the other species. 



COLEOCHAETE PULVINATA, A. Br. 



Fronds orbicular, upper surface rounded, about 2 mm high 

 in the middle, not thin, flat discs as C. scutata; the arrange- 

 ment of the filaments not so distinctly radiating from a 

 central cell or cells ; size of cells large, 35-40 // by 50-60 yw. 



