PALMELLACE^E. 185 



A very variable plant, not rare in ponds, but every new 

 cell found is somewhat unlike the previous one observed. 



Plate CLIX, figs. 19-23, five varieties. 



POLYEDRIUM MINIMUM, A. Br. 



Cells quadrangular; angles obtuse, sides more or less 

 deeply sinuate ; lateral view oval. Cells break in the mid- 

 dle and discharge gonidia. 



Diameter of cells, 8-10 /*. 



Often in large numbers in small pools. 



Plate CLIX, figs. 28-31, six cells in different positions ; 

 figs. 32-34 cells discharging gonidia. 



POLYEDRIUM LONGISPINUM, (Perty) Eab. 



Quadri-radiate, radii thin, elongated ; scarcely thickened 

 into a body in the center. 



Length of arms, 30-45 yw. 



A rare and peculiar species ; seems scarcely related to t 

 other forms described. 



Stagnant pond waters, the habitats of Desmids. 



Syn. Phycastrum longispinum, Perty. 

 Plate CLIX, figs. 35-38. 



POLYEDKIUM MUTICUM, A.Br. 



Cells triangular, somewhat compressed, angles rounded, 

 spineless, sides moderately compressed, membrane smooth. 



Diameter of cells, 12-15 /<. 

 Here and there in ponds. 

 Plate CLIX, fig. 24, three cells. 



Family XIV.PALMELLACE^l. 



Unicellular algae, cells either single, or numerous, consti- 

 tuting families, imbedded in a jelly to form a gelatinous stratum 

 which is amorphous ; tubular shaped ( Hormaspora ) ; variously 

 divided and perforate, ( Tetraspora ) ; falsely branched, (Hy- 

 drurus); or sometimes the jelly or mucus is wanting, (Ehaphi- 

 dium, Dactylococcus). Cytioderm mostly thin, often furnished 

 with a gelatinous, or homogeneous, or lamellate tegument. 

 Cytioplasm homogeneous, mostly at maturity distinctly granular, 

 green, or reddish or fuscous, always furnished with a chloro- 

 phylous vesicle, except Ehaphidium. 



