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150
THE MARINE ALGÆ OF NEW ENGLAND.
RHODYMENIA, (Grev.) J. Ag.
(From ροδεος [rodeos], red, and υµην [umen], a membrane.)
Fronds flat, membranaceous, dichotomous or palmate, composed of an internal layer
of large roundish-angular cells and a cortical layer of smaller cells, in some cases
arranged in short horizontal filaments; tetraspores cruciate, either collected in
superficial spots (sori) or scattered in the cortex; cystocarps external, sessile, with a
distinct carpostome, spores irregularly grouped in masses attached to a basal
placenta and surrounded by a gelatinous envelope.
A genus which formerly was made to include a large number of flat membranous species, a large part of
which have by recent writers been removed to other genera. We have but one species on our coast,
Rhodymenia palmata, the common dulse, of which, unfortunately, the cystocarpic fruit is unknown,
and the study of the fruit of the genus is out of the question with us.
R. PALMATA, (Linn.) Grev.; Phyc. Brit., Pls. 217, 218; Ann. Sci. Nat., Vol. Ill, Ser. 4,
Pl. 3, Fig. 8.—Dulse.
Fronds purplish red, broadly wedge-shaped, six to twelve inches long and four to
eight inches broad, irregularly cleft, palmate or dichotomous, sometimes repeatedly
laciniate, the margin often winged with leaflets; tetraspores cruciate, scattered in
patches over the frond, immersed in the cortex; cystocarps?
Var. Sarniensis.
Divisions very numerous, narrow, sublinear.
On Fuci, Laminariæ, and other algæ, between tide-marks, and extending into deep
water.
Common from New York northward; North Atlantic; California?
This, with Chondrus crispus, forms the only species eaten in New England. The present species,
although one of the commonest red sea-weeds in the North Atlantic, has never been known to bear
cystocarps, and hence the generic position is doubtful. The description given applies to the typical form,
and although the fronds are very variable in outline, the species is easily recognized. It is sold in the
seaport towns, where it is to be found dried on the fruit-stands of the women who sell green apples,
corn-balls, and other dainties. It is said to possess anthelmintic properties, which, if one can judge by
its disagreeable taste, is very probable.
PLOCAMIUM, Lyngb.
(From πλοκαµος [plokamos], a lock of hair.)
Fronds compressed, membranaceous, pinnately decompound, the pinnules
alternately secund in twos, threes, fours, or fives, composed of an inner layer of
longitudinal, oblong cells and a cortical layer of smaller polygonal cells; tetraspores
zonate borne in special branchlets; cystocarps