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180 THE MARINE ALGÆ OF NEW ENGLAND. frond in the Melobesioid group is that given by Rosanoff in his work already referred to. According to Bornet, however, the cystocarpic fruit of the Melobesiæ escaped the observation of Rosanoff, and what the latter called cystocarps were only a form of the non-sexual or tetrasporic fruit. The tetraspores are found in two different forms—either in hemispherical conceptacles, which have a single central orifice of good size, at whose base the spores are borne around a central tuft of paraphyses, or else in truncated conceptacles, whose flattened upper surface is perforated with numerous orifices, beneath each one of which is a tetraspore, separated from its fellows by a large, colorless cell. The fronds of the smaller species of Melobesia, as M. Lejolisii and M. farinosa, consist of two portions, the basal and the cortical. The former consists of a single layer of cells, which arise from the division of the spore into four cells and subsequent marginal growth. The cortical layer in the smaller species is composed of small cells cut off by oblique partitions from the upper part of the basal cells. In the larger species of Melobesia, more particularly those placed in the subgenus Lithophyllum, the cortical layer is much more marked, and the cells of which it is composed seem to be arranged in lines which are curved at the base, but are straight above and at right angles to the direction of growth. In some of the small species of Melanesia certain of the basal cells elongate and swell at the summit, so that when seen from above they look larger than the neighboring cells. Rosanoff applied to such cells the name of heterocysts, a word badly chosen, since the heterocysts in the Nostochineæ, where the term was first employed, cannot well be compared with the heterocysts in Melobesia. The conceptacles in all our species of Melobesia are external. The form generally found is that which contains the tetraspores. Our species all occur in Europe, and it is very probable that the remaining Northern European forms not yet recorded with us will be found on further search. a. Species small, growing on plants, basal stratum well marked, cortical layer imperfectly developed. M. LEJOLISII, Rosanoff. (M. membranacea, Aresch., in Agardh’s Spec. Alg.; Harvey, Phyc. Brit., Pl. 347, in part.—M. farinosa, Kütz., Spec. Alg.; Le Jolis’s Liste des Algues.—M. Lejolisii, Rosanoff, l. c., p. 62‚ Pl. 1, Figs. 1-12.) Fronds thin and brittle, at first orbicular but soon densely confluent, forming scaly patches of indefinite extent; heterocysts wanting, basal cells squarish, cortical cells few and indistinct; tetrasporic conceptacles very numerous, approximate, flattenedconvex, orifice ciliated; tetraspores four-parted; antheridia and cystocarps? On leaves of Zostera. Wood’s Holl, Mass.; common from Nahant northward; Europe. A species which is certainly common on eel-grass on the northern coast and probably equally abundant in Long Island Sound, although definite information on this point is wanting. This is the form which is found in American herbaria bearing the name usually of M. farinosa or M. membranacea. The orbicular character of the fronds soon disappears, as they are found in great numbers, and at an early stage become confluent. The conceptacles are so numerous that at times very little of the fronds themselves can be seen. The latter easily crumble and fall from the plant on which they are growing. M. FARINOSA, Lam.x. (M. farinosa, Aresch., in Agardh’s Spec. Alg., non Le Jolis’s Liste des Algues.—M. farinosa and M. verrucata? Harvey, in part.—M. farinosa, Lam.x., in Rosanoff, l. c.‚ p. 69‚ Pl. 2, Figs. 2-13.)
REPORT OF THE COMMISSIONER OF FISH AND FISHERIES. 181 Fronds thin, orbicular, becoming confluent, distinctly zonate; heterocysts present, basal cells elongated-rectangular, cortical cells semicircular or triangular seen from above; tetrasporic conceptacles small, hemispherical, orifice not plainly ciliate; tetraspores four-parted; antheridia and cystocarps? On Fucus vesiculosus. Wood’s Holl, Mass; in all parts of the world. Although only one locality is mentioned, the species probably occurs throughout our limits. It is distinguished from the last by the shape of the conceptacles and the absence of a circle of cilia around the orifice. The fronds are larger and more frequently orbicular, although scarcely thicker than in M. Lejolisii. In both species the calcareous incrustation is somewhat farinaceous as compared with the following, in which the incrustation is smoother and solid. M. membranacea, Lam.x. related to M. farinosa, but destitute of heterocysts and having tetrasporic conceptacles with several orifices, is to be expected on algæ of our coast. M. PUSTULATA, Lam.x. (M. pustulata, Phyc. Brit., Pl. 347 d; Rosanoff, l. c., Pl. 4, Figs. 2-8.) Fronds rather thick, circular, becoming reniform or orbicular, indistinctly zoned; heterocysts wanting, basal cells elongated vertically, cortical cells squarish; conceptacles large, hemispherical, orifice naked; tetraspores four-parted. Probably common on the larger algæ along the whole coast, but being undistinguishable from the next species when sterile, one cannot be sure of the species unless it is in fruit. The tetraspores of M. pustulata are zonately four-parted, while those of M. macrocarpa are merely two-parted at maturity. In both species the fronds are rather thick and solid and do not crumble, as in the two preceding species, and the orbicular shape is preserved for a longer time. M. MACROCARPA, Rosanoff. (M. macrocarpa, l. c.‚ p. 74, Pl. 4, Figs. 2-8 and 11-20.) Fronds as in M. pustulata; tetraspores large, two-parted. On Chondrus. Gloucester, Mass.; Europe. b. Species rather large, growing on stones and shells, cortical stratum well developed. M. LENORMANDI, Aresch. (Lithophyllum Lenormandi, Rosanoff, l. c., p. 85, Pl. V, Figs. 16,17; Pl. VI, Figs. 1, 2, 3, 5.) Fronds saxicolous, closely adherent to the substratum, suborbicular, Becoming squamulose-imbricate, slightly zonate, margin crenate, lobed; tetraspores fourparted, in compressed, hemispherical conceptacles, with numerous orifices; antheridia and cystocarps? On stones. Gloucester, Mass.; Europe. Apparently common in many places, but fruiting specimens were only collected at
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I.-THE MARINE ALGÆ OF NEW ENGLAND.
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REPORT OF THE COMMISSIONER OF FISH
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