COSMARIUM. 57 



distinct, converging at the apices. Color of older plants red- 

 disb brown. 



Diameter 50 fi ; length 90 //. 



Pond, MouDt Everett, Massachusetts, 1882. 



According to some author.- this plant might be classed with 

 Docidiiim, hut having no inflation at the base of the semi- 

 cells, and no plication in the cell-walls, I give it a place here. 



Genua, COSMARIUM, Corda. 



( Sella oblong, cylindrical, elliptical <>r orbicular with margins 

 Bmooth, dentate or crenate ; always more less deeply constricted 

 in the middle; ends rounded or truncate and entire, oof 

 emarginate, lobed nor Binuate ; end view oblong or oval, some- 

 times with a swelling in the middle of the longer sides: 

 chlorophyllous cytioplasm parietal, <>r more or less concentrated 

 in the centre of the semi-cells, or divided int<> two masses; 

 cytioderm, (cell-walls) smooth, punctate, warty, or very rarely, 

 spinous. Zygospore spherical, tuberculated or spinous, Beldom 

 Bmooth or angular. 



The plants of this genus are recognized by their -lent form 

 and entire end. They are usually about 1 I times as long as 

 wide; sometimes shorter and sometimes longer, rarely over 

 two diameters in length. Ends always entire, not emarginate 



or incised. 



They may he conveniently divided as follows 



1. ( Ihlorophyl parietal distributed "ii the inside of the walls of 



the cells. 

 'J. Chlorophyl more or less concentrated into one or two masses, 

 nuclei, in each semi-cell. 



| End view round, oval or elliptic withoul central infla- 

 tion. 



1. ( ytioderm (cell-wall l smooth, or punctate. 



2. ( ytioderm verrucose. 

 ''>. ( '\ tioderm spinons. 



I Kml view round, oval or elliptic with a central inflation 

 on each side. 



4. Cytioderm smooth or punctate. 



5. Cytioderm verrucose or spinous. 



C. ovale, Ralfs. Plate XIII, tigs. 8, 9. 



Large, oval or elliptical, nearly twiee as long as broad, ends 

 rounded; central constriction deep linear ; isthmus about one- 



