342 DESMIDE2E. 



mostly bicrenate. Endochrome frequently bipartite, in 

 the transverse view stellate, not filling entirely the cavity 

 of the cells. Reproduction by bodies analogous to zoo- 

 spores. 



Derivation. From Sea-os, a bond. 



a. Filaments with two angles. 

 * Mucous sheath very evident. 



1. DESMIDIUM CYLINDRICUM Grev. 

 Plate LXXXIII. Figs. 1, 2. 



Char. Filaments stout, somewhat compressed, with two bi- 

 crenate angles. Crenatures strongly marked. Cells 

 rather longer than broad, connected by a thickened border, 

 mucous sheath very evident. Endochrome four or Jive 

 rayed. 



Grev. Scot. Crypt. Flor. t. 293.; Desmar, n. 1110.; Harv. 

 in Manual, p. 196. Didymoprium Grevillei Kiitzing, 

 Phyc. Gener. Desmidium cylindricum Ralfs, in An- 

 nals, vol. xi. p. 378. pi. viii. fig. 1. 



Hob. Scotland : Dr. Greville. At the bottom of shallow 

 pools and ditches, Appin : Captain Carmichael. In old 

 peat pits about Dolgelly, North Wales ; sparingly near 

 Penzance : Mr. Ralfs. In a watercourse on Chiltington 

 Common, near Pulborough, Sussex : Mr. Jenner. Ches- 

 hunt : A. H. H. In Caragh Lake, Kerry : Mr. An- 

 drews. Bog holes, co. Meath : Mr. Moore. 



The above description embraces all the essential characters 

 of the species which may be regarded as the type of the 

 genus. In consequence of the spiral twisting of the filaments 

 the crenatures are much more perceptible in certain cells than 

 in others ; they are most strongly marked as a rule at about 

 every tenth cell, gradually diminishing from these towards 

 the central cells of the series, where they are much less ap- 

 parent, and where the extremities of the crenatures, instead 



