344 



b. Filaments triangular. 

 * Mucous sheath not apparent. 



3. DESMIDIUM SWARTZII Ag. 

 Plate LXXXIII. Figs. 7, 8. 



Char. Filaments triangular. Cells rather shorter than broad, 

 bicrenate, angles of the cells well marked. Endochrome 

 three-rayed. 



Grev. Scot. Flor. t. 292. ; Ehren. Die Infus. p. 140. t. 10. 

 f. 8. ; Pritch. Infus. p. 183. ; Harv. in Manual, p. 196. ; 

 Ag. Syst. p. 9. ; Ralfs, in Annals of Nat. Hist. vol. xi. 

 p. 375. plate viii. fig. 3. ; Jenner, in loc. cit. p. 192. 



Hab. Scotland : Dr. Greville. Appin : Captain Car- 

 michael. Tunbridge Wells : Mr. Borrer. Swansea, 

 South Wales ; Caernarvon and Dolgelly, North Wales ; 

 Penzance : Mr. Rolfs. High Beech, Epping : A. H. H. 

 Rusthall Common, and in a pond between Ramslye 

 rocks and Broadwater Forest; Battle; Chiltington Com- 

 mon, near Pulborough : Mr. Jenner. Bog holes, co. 

 Meath: Mr. Moore. 



In consequence of the filaments of this species being trian- 

 gular, the spiral twisting of the threads is more evident than 

 in any other species of the genus. When the microscope 

 is brought to bear upon any filament, two of the three lines 

 of crenatures are visible, and the third is indicated by a dark 

 waved line passing from one margin of the filament gradually 

 towards the other, the dark appearance of the line being 

 occasioned by the dense endochrome of the cells situated 

 immediately behind the crenatures. 



Kutzing limits the genus Desmidium to this one species, 

 which he considers to differ generically from the other species 

 usually associated with that genus, in the fact of the presence 

 of the third angle to the cells a distinction not considered to 

 to be sufficient in the case of the genus Staurastrum for 

 the foundation of new genera. The German professor has 



