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REPORT OF THE COMMISSIONER OF FISH AND FISHERIES. 149
On rocks at low-water mark.
Common from New York northward.
The common Irish moss which is used for culinary purposes, and also for clarifying beer. It is also said
to be used in the manufacture of cheap cotton cloths. Although very variable in shape, it is not likely to
be mistaken for any other species, except possibly sterile specimens of Gigartina mamillaris or
Gymnogongrus Norvegicus, which is, however, a rare species. When growing exposed to the light, the
color is a yellow-green.
SUBORDER RHODYMENIEÆ.
Fronds membranaceous or filiform, solid or tubular; antheridia forming superficial
patches; tetraspores tripartite, cruciate, or zonate, either scattered in distinct spots
or sometimes sunk in crypts; cystocarps external, containing densely packed
subdichotomous filaments, arranged in distinct masses around a basal placenta with
a thick pericarp, which is connected by numerous filaments with the placenta.
The present suborder is exceedingly ill-defined, and no two writers agree exactly as to its limits. In the
typical genera we find a distinct basal placenta on which are borne masses of spores, which when young
are seen to be formed of subdichotomous filaments, but which when mature are arranged without order
and held together by a gelatinous envelope. Diverging from the type, we have genera like
Cordylecladia, in which, even at maturity, the spores preserve to a certain extent a rnoniliform
arrangement, and we then have a cystocarp but little different from that of Gracilaria, which belongs to
the Sphærococcoideæ. On the other hand, we have the order connected with the Cryptonemieæ by
Chrysymenia, which is now placed by Agardh in the Rhodymeniaceæ. The position of Rhodophyllis and
Euthora is doubtful. Hero we have no distinct basal placenta, but rather a central placenta or
carpogenic cell, reminding one somewhat of the genus Rhabdonia and its allies, which have been
included in the Solierieæ. Euthora, at any rate, demands a more accurate study, and our own species of
Rhodophyllis, R. veprecula, does not well correspond with the typical members of the suborder in
relation to its cystocarpic fruit. Lomentaria and Champia agree with the Rhodymenieæ in their fruit,
although the fronds are peculiar, and we have kept them as a division of the present.
Tribe I. RHODYMENIEÆ proper.
Cystocarps with a basal placenta, fronds solid.
Fronds dichotomous or palmate..................................................... Rhodymenia.
Fronds pinnately compound.............................................................Plocamium.
Fronds filiform............................................................................ Cordylecladia.
? Tribe II. RHODOPHYLLEÆ.
Cystocarps with a central placenta, fronds membranaceous.
Tetraspores zonate, fronds dichotomous or pinnate...................... Rhodophyllis.
Tetraspores cruciate, fronds dentato-pinnate ........................................ Euthora.
Tribe III. LOMENTARIEÆ.
Cystocarps with a basal placenta, fronds tubular.
Fronds constricted at the joints, but with no proper diaphragms, tetraspores sunk in depressions of the
frond......................................................................................... Lomentaria.
Fronds with numerous diaphragms, tetraspores superficial ................ Champia.