108 DESMIDS OF THE UNITED STATES. 



Passaic County (Wood Lake), N. J. 



This species does not strictly conform to the description of 

 the author, but it has so much in common that with his con- 

 sent, I adopt the name he chose for his Brazilian plant. 



Genus, MICRASTEKIAS, Ag. 



Cells simple lenticular, deeply constricted in the centre ; viewed 

 from the front, orbicular, or broadly elliptical ; from the vertex 

 fusiform with acute ends. Semicell three to five lobed; lateral 

 lobes entire or incisely-lobulate ; end or polar lobe entire or sinuate 

 or emarginate, and sometimes with angles produced and bifid. 



In but few species have the zygospores been detected ; they are 

 large, globular and furnished with stoul -pine-, which are at first 

 simple, then become branched at the ends. 



Section I. Cell circular ; segments five-lobed ; lobes approximate, the end lobe 

 narrower. 



M. Torreyi, (Bailey,) Ralfs. Plate XXX. figs. L-8. 



Circular; lateral lobes deeply incised, making two or three 

 subdivisions to each j all more or less tapering, and acute or 

 bidentate at the extremities. End lobe narrow, not exserted, 

 dilated at apex, concave, angles taper into acute points or 

 spine-. 



Diameter 25O-300 //. 



Frequent in ponds of New Jersey, Mt. Everett, Mass., 

 and few localities in Pennsylvania. 



Often variable in the number and form of the subdivisions. 

 Plate XXX represents eight varieties, the result of multi- 

 plication by dividing. Compare Introduction, page 18. 



M. Pseudotorreyi, Wolle. Plate XXXII, fig. 1. 



Large, circular, five-lobed ; basal and intermediate lobes bi- 

 sected, sections more or less conical, ends deeply furcate ; polar 

 lobe broadly cuneate, end truncate-sinuate, angles cuspidate. 



Diameter of cell 180 fi. 



Mt. Everett, Mass. 



Separated from M. Torreyi, by its smaller size, the less 

 number of lobules and their greater similarity of form. 



