The English flora - SeaweedAfrica

364 ALG/E CONFERVOIDEiE. [Stylone ma.
authentic specimen of which I have compared our plant. The only
difference I can perceive lies in the generic character, and this I am almost
inclined to suspect, depends on age ; for I find the apices of the
branches simply striated, like a Calothrix or Scytonema, and the smaller
branches, for at least part of their length, have thesemipunctate appearance
of Scyt. ocellatum; and it is only in the' larger and main branches
that the punctated character is clearly visible. Should my ideas prove
correct, the Stigonemata must only be regarded as Scytonemata, arrived
at full perfection.
72. Scytonema. Ag. Scytonema.
Filaments branched (very rarely simple), flaccid, tough, continuous,
tubular. Endochrome brown or olivaceous, transverse-
ly striated, " at length separating at the striae into lenticular
sporidia." Carm.—Name; gxvroc, a skin, and vrn^a, a thread;
in allusion to the toughness of the filaments.—Agardh strangely
places this genus between Trentepohlia and Protonema, with
neither of which has it the least affinity. Captain Carmichael,
whom I gladlyl follow in removing it to the Oscillatoriece,
remarks, with his usual acuteness, the strong affinity that sub-
sists between it and Lyngbya, " the internal structure of the
filaments being nearly, if not absolutely, the same in both :
that is, the filaments in botii are continuous tubes, filled with a
transversely striated granular mass, which at length separates
at the striae into lenticular sporidia." Carm. MSS.— Scytonema
is still more closely related to Calothrix, from which I
find it very difficult to distinguish it by a satisfactory char-
acter.
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1. S. ocellatum, Harv. (beaded Scytonema); filaments long
gelatinous pale-brown flexuose, branches solitary slightly con-
stricted at the base obtuse divaricating.— Conferva ocellata,Dillw.
Syn. Conf.p. 60. t. D E. Bot. t. 2530. (not S. ocellatum, Lyngb.
Hydroph.Dan. t. 28.) S. myochrous, (3. ocellatum, Ag. Syst. Alg.
p. 40, (according to the references to Dillw. and E. Bot.)
Alpine bogs. Filaments tufted, erect or decumbent, gelatinous, pale
yellow- brown, twice or thrice as thick as those of S. myochrous,
branched; branches irregularly disposed, issuing from the centre of
the filament, somewhat attenuated at their base, very obtuse and
slightly thickened at the extremity, erecto-patent, solitary or extremely
rarely in pairs, the larger ones with a few short ramuli. Sporidia distant,
broad, at first quadrate, but becoming sphaerical and finally longitudinally
divided into two portions; .margin of the filament very broad.
Agardh is surely not acquainted with the true Conf. ocellata of British
authors, or he would scarcely have confounded it with S. myochmus,
from which it differs in every, save the generic, character. Dillwyn
well remarks, that it is most nearly allied to Stigonema atro-virens, and
it seems indeed to be intermediate between Scytonema and Stigonema;
the division of the sporidia, in old filaments, assimilating it to the latter
genus. Lyngbye's figure and description belong to S. myochrous.
2. S. compdctum, Ag. (compact Scytonema); " filaments de-
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