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86
THE MARINE ALGÆ OF NEW ENGLAND.
siliculose, composed of three to six cells, formed from the terminal cells of peripheral
filaments, often secund on the upper side.
On sand-covered rocks and algæ at and below low-water mark.
Wood’s Holl, Nahant, Gloucester, Mass.; Portland, Maine, Mr. Fuller; Europe.
A species which is rather common in the spring months, but which disappears with us about the 1 st of
July. The fronds are more slender than in M. vermicularis, but when dried under too great pressure, or
when allowed to remain some time in fresh water, they somewhat resemble that species. The
distinction is best seen in the peripheral filaments. Those of M. vermicularis are shorter, decidedly
clavate, less curved, and are formed of spheroidal cells In C. virescens they are longer, more nearly
cylindrical, recurved, and formed of ellipsoidal cells. The number and size of the plurilocular sporangia
vary very much.
C. ZOSTERÆ, (Mohr.) Thuret. (Myriocladia zosteræ, Ag.—Mesogloia vermicularis, var.
zosteræ, Kütz., Spec. Alg.—M. virescens, var. zostericola, Harv., Phyc. Brit., Pl. 82.—
M. zosteræ, Aresch., in Ner. Am. Bor.‚ Vol. I, p. 127, Pl. 10 a.) Pl. 7, Fig. 2.
Fronds filiform, gelatinous, three to eight inches long, subsimple, furnished with a
few short, remote branches, given off at wide angles; peripheral filaments erect,
rather rigid, cylindrical below, moniliform above; cells spheroidal, .02-4 mm in
diameter; unilocular sporangia ovate; plurilocular sporangia siliculose, composed of
three to six cells, usually forming dense tufts on the upper part of the peripheral
filaments.
On eel-grass.
Wood’s Holl, Gloucester, Mass.; Europe.
A small species with very few branches, which, although it has been by some considered a variety of C.
virescens, is sufficiently distinct both in its microscopic structure and the season of growth. C. virescens
is a spring form, which disappears in early summer, while C. Zosteræ, at least on our coast, occurs in
summer and autumn. The appearance of the peripheral filaments is different in the two species. In C.
virescens they are slender and curved and in C. zosteræ rather stout and erect and more densely packed
together, in this respect resembling M. vermicularis, in which, however, the filaments are distinctly
clavate and moniliform, and do not produce plurilocular sporangia at the extremity. A section of the
frond of a well-developed C. virescens shows a circle of roundish cells around a central cavity and on the
outside a series of branching filaments, which end in the proper peripheral filaments and sporangia. In
C. Zosteræ there is also a circle of cells surrounding a central cavity, but the peripheral filaments seem
to be given off directly from the circle of cells. The figure in the Nereis Am. Bor. does not correctly
represent the structure of C. Zosteræ, for the clusters of peripheral filaments are not outgrowths from
special colored filaments, but from the uncolored cells. American specimens agree perfectly with the
specimens of Mesogloia zosteræ, No. 100, of Areschoug’s Alg. Scand.
FAMILY RALFSIEÆ.
Fronds horizontally expanded, sometimes crustaceous; fructification in raised spots
(sori), composed of few-celled club-shaped paraphyses and spheroidal unilocular
sporangia.