348 DESMIDE^. 



noticed by Mr. Ralfs and Mr. Jenner nearly simultaneously. 

 The processes are not present at all the angles of every cell, 

 but only at those angles which have been for the longest 

 period formed : thus, when a cell has become but recently 

 divided no processes are present on the newly formed angles 

 which result from this division. Owing to the existence of 

 the highly developed mucous sheath, the filaments are dis- 

 posed often as in the previously described species parallelly. 



Mucous sheath much broader than in G. dissiliens, but less 

 perceptible. 



53. SPEUEROZOSMA Corda. 



Char. Filaments very fragile, compressed, consisting of bipar- 

 tite cells united by means of gland-like processes, and much 

 constricted between each cell. 



This genus is distinguished from the previous genera by 

 its compressed frond, and by the glandular processes at the 

 junction of the celjs. 



1. SPH^ROZOSMA ELEGANS Corda. 

 Plate LXXXIV. Fig. 1. 



Char. Cells smooth, rather longer than broad, deeply divided 

 on each side into two portions. Glands single, one in the 

 centre of each margin. 



Sphcerozosma elegans Corda, Almanac de Carlsbad, 1835, 

 t.iv. f. 37. Odontella? unidentata Ehr., Infus. p. 159. 

 Desmidium compressum, Annals of Nat. Hist. vol. ix. 

 p. 253. Schistochilum Ralfs, unidentatum Jenner, in Fl. 

 of Tunbridge Wells, p. 192. Desmidium vertebratum 

 Breb. et Godey. 



Hob. Chyan-hal Moor, near Penzance ; and Towednack 

 Moor, near St. Ives : Mr. Ralfs. Rotherfield, and in 

 Jack's Wood spring : Mr. Jenner. 



For the figures of this and the following species I am in- 

 debted to Mr. Jenner. 



