m
ZU Berlin, 1833, p. 318. X . fasciculatum Ehr., Infus.
p. 147. tab. X. fig. xxiv. b. Xanthidium fasciculatum
Ilalfs, in Annals, vol. xiv. p. 166. fig. 3. c. d. e. Cosmarium
acideatum Menegh., 1. c. p. 218. Euastrum
No. 10., Bailey’s Amer. Bacil. p. 296. pl. i. fig. 10. ;
Jenner, in loc. cit. p. 194.
This species is smaller than the following, the segments of
a dificrent form, and the spines more numerous.
3. X anthidium polygonum Hass.
Plate L X X X IX . Fig. 4.
Char. Frond polygonal. Segments four-angled. Spines
eight to each segment, in pairs, situated at the angles.
Xanthidium fasciculatum fl polygonum Ehr., Infus. p. 148.
t. 10. fig. 24. a. Xanthidium fasciculatum fl polygonum
Ealfs, in Annals, vol. xiv. p. 467. pi. xii.
fig. 3. a. b.
Hah. Near Dolgelly : Mr. Ralfs. Near Tunbridge Wells :
31r. Jenner.
This doubtless ought not to he regarded as a variety, but
as a distinct species, differing from Xanthidium fasciculatum,
of which it has hitherto been regarded as a variety, in being
altogether a much larger plant, in the polygonal form of the
segments, and in the number of the spines to each segment,
which are eight in X . polygonum, arranged in four pairs, while
in X . fasciculatum they are twelve, disposed in six pairs.
4. X anthidium aculeatum Ehr.
P late L X X X IX . Pig. 3.
Char. Segments reniform, almost globose. Spines single,
marginal, and scattered.
Xanthidium aczJeafem Ehr., Infus. p. 147. tab. 10. fig. 23.;
Menegh. 1. c. p. 224.; Ralfs, in Annals, vol. xiv. p. 467.
pi. xii. fig. 2. a. b. c. d.
Hab. Ashdown Forest, and near Cross in Hand : Mr.
Jenner. Penzance : Mr. Ralfs.
This species differs from X . fasciculatum principally in the
spines being single and not in pairs as in that species.
“ In the centre of each segment, on both surfaces, is a projection
similar to th a t described under X . furcatum, hut less
evidently dentated.”— Ralfs.
57. C Y L IN D R O C Y S T IS Menegh.
Char. Yvonà mucous, indefinite. CovpnsQ\.Q& cylindrical, filled
with sporidia, copulating, at length bearing two spores
transversely divided into halves.
Derivation. From KvXivSpos, a cylinder, and Kvarns, a cell.
1. Cylindrocystis B rebissoni Menegh.
Plate X C I I. Fig. 17.
Char. Cells cglindrical, two or three times longer than broad,
with rounded extremities.
C. Brebissoni Menegh., Monog. Nostoc. Italic.
Hab. Sussex : Mr. Jenner. High Beech : A . H. H.
Aberdeen : Dr. Dichie. Cal way ; M ‘ Colla.
This is a particularly interesting production, as it seems to
form a direct link between the Protococcoideæ and the Desmideæ,
and by Meneghini himself is placed in the family
Nostochineoe. The conjunction of the cells, as well as their
great size and regular form, have induced me to refer it to the
Desmideæ, in which the phenomenon of union of the cells is
of such frequent'occurrence. The frond does not appear to
be divided in the centre as in most true Desmideæ.
58. CO SM A R IUM Corda.
Char. Frond constricted in the middle. Segments fr e -
quently as broad and sometimes broader than long, neither