il
■; ‘Umostly
Mcrenate. Endochrome frequently bipartite, in
the transverse view stellate, not filling entirely the cavity
o f the cells. Reproduction by bodies analogous to zoo-
spores.
Derivation. From Bsagos, a bond.
a. Filaments with two angles.
* Mucous sheath very evident.
1. D esmidium c t l in d k ic um Grev.
Plate L X X X I I I . Figs. 1, 2.
Char. Filaments stout, somewhat compressed, with tivo bi-
crenate angles. Crenatures strongly marhed. Cells
rather longer than broad, connected by a thickened border,
mucous sheath very evident. Endochrome fo u r or fiv e
rayed.
Grev. Scot. Crypt. Flor. t. 293.; Desmar, n. 1110.; Harv.
in Manual, p. 196. Didymoprium Grevillei Xiiitzing,
Phyc. Gener. Desmidium cylindricum Ralfs, in Annals,
vol. xi. p. 378. pi. viii. fig. 1.
Hab. Scotland; Dr. Greville. A t the bottom of shallow
pools and ditches, Appin : Captain Carmichael. In old
peat pits about DolgeUy, North Wales; sparingly near
Penzance : Mr. Ralfs. In a watercourse on Clnltington
Common, near Pulborough, Sussex: Mr. Jenner. Cheshunt
: A. H. H. In Caragh Lake, K e r ry : Mr. A n drews.
Bog holes, CO. Me ath: 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 ceUs than
in others ; they are most strongly marked as a rule a t about
every tenth cell, gradually diminishing from these towards
the central cells of the series, where they are much less apparent,
and where the extremities of the crenatures, instead
of being pointed are truncate. This species, as well as indeed
all the Desmideæ, are most beautiful microscopic objects.
I do not see the necessity for instituting a new genus for its
reception. I have not, therefore, adopted tha t of Kützing ;
viz. Didymoprium.
** Mucous sheath not apparent.
2. D esm idium B o r e e e i Ralfs.
P late L X X X I I I . Figs. 9, 10.
Char. Filaments slender. CeUs biangular, infiated, elongated,
being about twice as long as broad. Endochrome fiv e or
six rayed.
Desmidium Borreri Ralfs, in Annals of Nat. H is t, vol. xi.
p. 375. t. 8. p. 4. Didymoprium Borreri Jenner, in
Fl. Tunbridge Wells, p. 192.
Hab. Boggy ditch at Crom Bychan : Mr. Borrer. Llyn
y Cwyn : Mr. Borrer and Mr. Ralfs. In all peat bogs
near the outlet of Llanberris Lakes and near DolgeUy,
North Wales : Mr. Ralfs. On Ashdown Forest near
Duddles WeU ; In the great bog near Forest Row, and
at Chiltington Common, near Pulborough : Mr. Jenner.
Bog holes, CO. Meath : Mr. Moore.
This Is one of the most graceful and easily recognised species
of the genus, remarkable principally for the great length
of the cells ; the endochrome in each cell is distinctly divided
into two masses, which arrangement imparts to the plant
somewhat the appearance of a Tyndaridea.
The cells are somewhat Inflated, and each resembles in
form two flower-pots juxtaposed by their mouths ; the rims
being represented by the crenatures of the cells, between
which passes circularly round each cell a superficial groove,
in the situation of which the cells at an advanced period of
their developement separate, and give issue to their granular
contents. Viewed transversely, the cells are spherical, with
sUght lateral projections.