iSi
respond witli the genus aa defined by Mr. Berkeley or
myself, neither does his genus Sirosyphon answer to the
genus Hassallia, formed by Mr. Berkeley for those species
hitherto associated with the genus Scytonema, but which the
definition of that genus, as it at present stands, does not
embrace.
The following is Kiitzing’s definition of Scytonema ; —
“ Trichomata vagina duplici, firma crassiuscula colorata
arete inclusa ramosa ; rami ex continuatione trichomatis in-
terni et prolongatione vaginæ oriundi, non basi iis discreta.
Spermatia ex articulis intumescentibus progenita.”
In the genus as thus characterised, Kiitzing includes the
folloAving British species. Scytonema cerugineo-cinereum
( Ocellatoria rupestris, Grev. Scot. Flor. Turf. 246. ?), S. my-
ochrous, S. turfosum, and S. compactum. Now out of these
four species there is but one which could be received into
the genus Scytonema of Mr. Berkeley, and that one is Scyt.
myochri)us. I t is clear, therefore, th a t there is no correspondence
hetAveen the genus Scytonema of Berkeley and tha t of
Kiitzing.
1. Scytonema hibernicum Hass.
P late L X V I I I . Fig. 1.
Char. Filaments o f considerable diameter. Cells about as
long as broad, issuing in pairs at right angles with the
stems.
Scyt. hibernicum Hassall, MS.
Hab. On a clayey bank, co. Antrim, Ireland: Mr.
Moore.
Of this beautiful species I have seen but a single specimen.
I t Avas sent to me by Mr. Moore, Avith the name of Scyt.
ocellatum upon it, with which plant however it has no affinity.
The cells are of exactly the same form as in Scy.
myochrous, from which it differs principally in being altogether
larger.
2. S cytonema myochrous Ay.
Plate L X V I I I . Fig. 2.
Char. Filaments o f less considerable diameter, elongate, mostly
decumbent and fiexuous.
Lyngb. t. 297. and S. ocellatum Lyngb. t. 28. Conf.
myochrous Dillw. Conf. t. 1 9 .; F . B. t. 1555. Conf. mi-
rahilis, F . B. 2219. (not of D íIIaa-.) Scytonema con-
textum Carmichael.
Hab. Various parts of Wales: Mr. Dillwyn and Mr.
Woods. Neighbourhood of B a n try : Miss Hutchins.
Crowborough Warren, and in Pressbridge Warren, near
Wych Cross : Mr. Jenner. Dolgelly : Mr. Ralfs.
This species differs from the previous one only in being
smaller in all its parts. I have no doubt of the correctness
of Scyt. contextum as a synonym, having, through the kindness
of Mr. Harvey, had an opportunity of examining an
authentic specimen. Carmichael thus describes i t : — “ Thi-
species occurs in a thin, closely matted blackish fleece, of ins
determinate extent. Filaments two or three lines in length,
simple, or rarely furnished with one or two branches,”
(which are occasionally geminate, as in S. myochrous), “ interwoven
into an almost inextricable stratum. Sporidia, when
visible, which rarely happens, globular and rather distant.
Besides the comparative shortness of the filaments, and the
more intimate contexture of the stratum, this species differs
from S. myochrous in becoming, Avhen dry, of a light greyish-
green colour instead of black.” — Carm. M S S .
25. P F T A L O N FM A Berk.
Char. Frond composed o f fla t, branched or simple filaments,
the margins membranaceous and striate.
Derivation. From ttstoXov, a leaf or lamina, and vyga, a
thread ; in allusion to the singularly Avinged filaments.