i»
Huh. On tlie trunk of a living elm at Oundle, Nortli-
amptonsliire: Rev. 31. J. Berkeley.
I doubt much ivlietlier this species be a true Hassallia.
I t is iiiuch more hke an Oscillatoria, the filaments being simple,
of equal diameter, regularly striated, and very brittle. The
only character which seems to unite it with Scytonema is its
erect habit. I t might possibly be better placed in Kiitzing’s
genus Symphosyphon; if not, it should perhaps form the type
of a neiv genus. The genus Symphosyphon is thus characterized.
“ Trichomata erecta vel adscendentia, vagina cartilagínea
multistriata (lamellosa) saipe fasciculata, involuta, basi confluentes,
laterahter concreta.”
5. H as sallia? limbata
Plate L X V I I . Fig. 6.
Char. “ Filaments thick, flexuous, ceruginous, loith a hroad,
pellucid margin, loosely interwoven in a dense dull oeru-
ginous green stratum.”— Grev.
O. limbata Grev. Crypt. Flor. Syn. p. 40. and t. 246.
(O. rupestris). Scytonema cerugineo-cinereum Kiitzing,
Phyc. General, p. 214. Ocellatoria limbata Harv. in
Hook. Brit. Flor. p. 3 7 5 .; also in Manual p. 164.
Hab. On perpendicular rocks, exposed to the trickling of
Avater, Pentland Hills : Dr. Greville.
On first examining an au th en tic specimen o f th is plan t, I
Avas impressed Avith th e idea th a t it o u g h t to be re fe rred to
th e genus Scytonema, h u t from n o t discovering branches on
th e filaments, I did n o t feel q u ite certain on th is point.
Kiitzin g having made th e species th e ty p e of his genus Scytonema,
th e re can be b u t little doubt h u t th a t it really
belongs to th e family Scytonemece. “ P la n t covering th e face
o f th e rock for several inches together, and when old, peeling
off in ra th e r large pieces. F x te rn a lly it is mostly of a dull
and hroAvnish green colour, b u t within more o f a verdigris
green, differing in in ten sity in different p a rts ; here and
th ere gelatinous and semi-transparent. Filamen ts th ick for
th e ir length, very flexuous, Avith a pellucid colourless limb,
equal in bread th to th e coloured, stria ted portion, Avhich is of
a pale verdigris g re en .” — Grev.
24. S C Y TO N FM A A ^ .
Char. “ Branches increasing by the protrusion and division
o f the central row o f cells.” — Berk, in lit.
Derivation. From u k v t o s , a skin, and vyga, a thread; in
allusion to the toughness of the filaments.
The genus Scytonema has h ith e rto evidently embraced the
description of plants belonging to tAvo distinct genera.
The above, therefore, is Mr. Berkeley’s definition of the
genus Scytonema, as very properly proposed to be restricted
by tha t gentleman a considerable time ago. This concise definition
briefly describes the essential character of the altered
genus, but there are also others Avhich serve to distinguish its
species from those which have hitherto been associated Avith
Scytonema, and which confirms the view adopted by Mr.
Berkeley of the necessity of forming two genera out of those
species. From the protrusion and division of the central
row of cells, it follows tha t the branches should frequently
be in pairs, and this is generally the case : the filaments,
also flaccid, of nearly equal diameter, are rarely moniliform.
The definition of the reconstructed genus Scytonema might
stand more fully thus : —
Char. flaccid, o f nearly equal diameter. Branches
usually in pairs, and formed by the protrusion and division
o f the central row o f cells. Cells generally quadrangular,
rarely i f ever regularly moniliform.
Kiitzing, in his “ Phycologia Generalis,” has removed one
species from the genus Scytonema, S. ocellatum, and formed
for it a ncAV genus Sirosyphon; but still the genus Scytonema
of Kützing does not in the most remote degree cor