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THE MARINE ALGÆ OF NEW ENGLAND.
NEMASTOMA.
(From νηµα [nema], a thread, and στοµα [stoma], a mouth.)
Fronds gelatino-carnose, compressed-cylindrical or plane, dichotomous or
subpinnate, composed of an axial layer of densely woven longitudinal filaments,
from which are given off short, lateral, dichotomous, fastigiate filaments, which are
united by a gelatinous substance to form a peripheral layer; tetraspores cruciate,
borne in the peripheral layer; antheridia borne on the superficial cells of the
periphery; cystocarps (favellæ) buried in the peripheral layer, spores escaping by a
narrow opening between the peripheral filaments.
A genus comprising not far from a dozen species, which inhabit principally the warmer waters of the
globe, the genus being particularly well represented in Australia. The fronds of the different species
vary from only slightly compressed and linear to broad and palmate, and in G. marginifera the frond
resembles in shape that of Rhodymenia palmata. The substance is rather gelatinous and the
microscopic structure resembles very closely that of the fronds of some of the Nemalieæ. The fruit of N.
marginifera is described by Bornet, in Notes Algologiques, as being a true favella like that of
Callithamnion. The genus is generally placed near Gloiosiphonia, and, like that genus, closely connects
the Ceramieæ with the Cryptonemeæ.
N. (?) BAIRDII, Farlow, Proc. Am. Acad. Arts and Sciences, 1875, p. 351.
Fronds purplish-rose colored, gelatinous, four inches long, one inch wide below,
vermiform, once or twice dichotomously divided, axils acute, apices attenuated;
tetraspores cruciate, borne on the tips of the peripheral filaments; cystocarps
Washed ashore at Gay Head, W. G. F.
A very rare species, of which only a single specimen is known. It was found on the beach near the lighthouse
at Gay Head, Mass., in company with Scinaia furcellata, in August, 1871. The specimen was a
fragment, without the base of the plant, but with abundant tetraspores, which were borne on the tips of
the peripheral filaments. In the absence of cystocarpic specimens the genus cannot be ascertained with
certainty, and botanists who visit Gay Head, should seach [sic] for the plant by dredging off the Devil’s
Bridge in five to ten fathoms. The specimen collected was at first supposed to be a portion of a broad
specimen of Nemalion purpureum, a species not yet known on our coast. The peripheral filaments are
loosely united together by a gelatinous mass, as in the subgenus Gymnophlæa of Agardh.
SUBORDER DUMONTIEÆ.
Fronds tubular, branching or proliferous; cystocarps immersed in the frond,
composed of a single mass of irregularly placed cells, similar in most respects to
those of the Cryptonemieæ.
A small suborder, included by Harvey in the Cryptonemieæ. The development of the cystocarps is not
well known, and on our coast there is no material to be obtained for the study of the suborder. The
common Dumontia filiformis of Northern Europe is wanting with us, and the genus Halosaccion, of
which we have one representative,