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62
THE MARINE ALGÆ OF NEW ENGLAND.
As an account of the families into which the suborder is divided has already been given on pp. 15-17, it
is unnecessary to repeat them here, but the reader will find them briefly described in their order on
subsequent pages, together with a synopsis of the genera found on our coast belonging to each family.
FAMILY SCYTOSIPHONEÆ.
Fronds unbranching, either membranous or tubular; plurilocular sporangia in short
filaments, densely covering the whole surface of the fronds; unilocular sporangia not
well known.
Fronds expanded membranes ................................................Phyllitis.
Fronds tubular.................................................................. Scytosiphon.
PHYLLITIS, (Kütz.) Le Jolis.
(From φυλλιτης [phyllites], a name given by Dioscorides to an unknown plant.)
Fronds olive-brown, simple, membranaceous, composed of a cortical layer of minute
colored cells and an internal layer of larger, oblong, colorless cells, which are
sometimes prolonged downwards in the form of short filaments; plurilocular
sporangia formed from the cortical cells, covering the surface of the fronds,
consisting of a few (4-6) cells arranged in short filaments, which are closely packed
together at right angles to the surface of the fronds; unilocular sporangia and
paraphyses unknown; growth from the base.
A genus consisting of two species, formerly placed in the genus Laminaria in consequence of their
membranous habit, but differing essentially from the true Laminariæ in the structure and disposition
of their sporangia.
P. FASCIA, Kütz. (Laminaria fascia, Ag.)
Fronds gregarious from a disk-like base, three to six inches long, a quarter to half an
inch wide, linear-elongate, contracted at the base into a short stipe.
Var. CÆSPITOSA. (Phyllitis cæspitosa, Le Jolis, Études Phycol., p. 10, Pl. 4.—
Laminaria cæspitosa, Ag.—Laminaria fascia, Harv., in Phyc. Brit., Pl. 45.—
Laminaria debilis, Crouan, Alg. Finist., No. 81.) Pl. IV, Fig. 3.
Fronds stipitate, cuneiform, often falcate and undulate.
Very common on stones between tide-marks; widely distributed over all parts of the
world.
About the limits of the present species there is a diversity of opinion. Le Jolis regards the L. fascia and
L. cæspitosa of Agardh as distinct species, but by Harvey they were considered as merely different
forms of the same species. Harvey’s opinion seems to us to be correct, for it is impossible to draw the
line between the two forms as found on our coast.