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REPORT OF THE COMMISSIONER OF FISH AND FISHERIES. 177
are tropical, Australia being especially rich in species. The genus is divided into a number of subgenera,
and is connected by Bostrychia and Tænioma with Polysiphonia. The tetraspores are in stichidia borne
on the hair-like branchlets, while in Bostrychia they are in the polysiphonous branches, and in
Tænioma the stichidia are formed from the flattened and scarcely altered branches. The cystocarps are
borne on short lateral branches, which are usually slightly prolonged beyond the base of the cystocarp.
The placenta of Dasya differs somewhat from that of Polysiphonia and our other genera of Rhodomeleæ.
The spores are pyriform, but are borne on rather long branching filaments which surround the
carpogenic cell at the base of the conceptacle, and which rise high up in its interior instead of being
nearly sessile around the carpogenic cell, as in Polysiphonia. The development of the cystocarp has
been studied in detail by Janczewski in D. coccinea. The fronds are either filamentous or more or less
flattened, and, as in the case with most of the suborder, are formed from a monosiphous axis, from the
cells of which whorls of filaments are given off, which in the older parts of the frond become parallel to
the axis and replace the siphons of Polysiphonia. In most of the genus there are also secondary siphons
and corticating cells, and either at the tip or throughout the frond tufts of delicate, dichotomous,
monosiphonous branchlets, which are colored and not hyaline, as in the hairs of some other genera.
D. ELEGANS, Ag., Sp. Alg. (Rhodonema elegans, Martens.—Dasya pedicellata, Ag.,
Syst.; Bailey, in Am. Journ. Sci., Vol. Ill, p. 84.)—Chenille. Pl. XV, Fig. 1.
Exs.—Alg. Am. Bor., Farlow, Anderson & Eaton, No. 51.
Fronds diœcious, villous, lake-red, six inches to three feet long, cylindrical, attached
by a small disk, alternately 1-3 pinnate, with a percurrent axis, densely clothed
throughout with tufts of purple, capillary, monosiphonous, dichotomous branchlets,
sections of branches showing five cells around the axial cell; antheridia densely
covering the lower cells of one of the divisions of the branchlets; tetraspores in two or
three rows in linear-lanceolate or ovate pointed stichidia on the branchlets;
cystocarps sessile on very short branches (pedicels) which are borne on the main
branches.
On Zostera, wharves, &c., below low-water mark.
Common from Cape Cod southward; Adriatic Sea.
A beautiful species, known to lady collectors by the name of chenille, at once recognized by its long,
cylindrical, branching fronds, densely fringed with fine lake-colored filaments. It is found throughout
the year. In drying it adheres closely to paper. The antheridia are much like those of Polysiphonia
variegata, but are longer. The species extends to the West Indies, but appears to be more common in
Long Island Sound than elsewhere. There is in the collection of the Peabody Academy of Salem a very
large specimen, said to have been collected at Ipswich Beach, Mass., but the locality must be regarded
as doubtful. At any rate, the species is quite unknown elsewhere north of Cape Cod.
SUBORDER CORALLINEÆ, Decaisne.
Fronds rose-colored or purple, calcareous, horizontally expanded or erect and
branching, crustaceous, foliaceous, or filiform, continuous or
S. Miss. 59——12