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 disposed
often as in the previously described species parallelly.
Mucous sheath much broader than in G. dissiliens, but less
perceptible.
53. S PH iE R O ZO SM A Corda.
Char. Filaments very fragile, compressed, consisting o f bipartite
cells united by means o f 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 cells.
1. Sphajkozosma elegans Cor da.
Plate L X X X IV . Fig. 1.
Char. Cells smooth, rather longer than broad, deeply divided
on each side into tioo portions. Glands single, one in the
centre o f each margin.
Spharozosma elegans Corda, Almanac de Carlsbad, 1835,
t. iv. f. 37. Odontella? unidentata YArc., \v£ns. p. 159.
Desmidium compressum. Annals of Nat. Hist. vol. ix.
p. 253. Schistochilum Ralfs, unidentatum Jenner, in Fl.
of Tunbridge 4Vells, p. 192. Desmidium vertehratum
Breb. et Godey.
Hah. Chyan-hal Moor, near Penzance ; and Towednack
Moor, near St. Ives : Mr. Ralfs. Rotherfield, and in
Ja ck ’s Wood sp rin g : Mr. Jenner.
F o r the figures of this and the following species I am indebted
to Mr. J enner.
2. Sphaieozosma excavatum.
Plate L X X X IV . Fig. 2.
Char. Cells longer than broad, excavated laterally, with two
glands or teeth at each margin.
Schistochilum excavatum Kalfs, M S .; Jenner, in Flora of
Tunbridge Wells, p. 192.
Hab. In a boggy spot near Cross in Hand, opposite to
where the road branches to Hailsham; bogs at Fisher’s
Castle, and in a pond between Ramslye and B roadwater
F orest: Air. Jenner.
A very distinct and interesting species.
Section ii.
Frond not forming filaments.
54. G O N IO CY ST IS Hass.
Char. Cells angular.
Derivation. From gcovia, an angle, and kvcttis, a cell.
Section i. T r ig o n o c y s t i s Hass.
Char. Cells with three angles.
Derivation. From Tpigcevoi’, triangular, and KvaTLS, a cell.
1. T rigonocystis o r bicu lar is Hass.
Plate L X X X IV . Fig. 7.
Char. Frond smooth, suhorbicular. End view triangular.
Angles obtuse.
Staurastrum orbiculare Meneghini, Synop. Desmid. p. 225.
Desmidium orbiculare Ehr., Infus. p. 141. tab. 10. fig. 9.
Staurastrum orbiculare Ralfs, in Annals, vol. xv. p. 152.
pi. X . fig. 4. a. b. c. ; Jenner, in loc. cit. p. 192.