180 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



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 Meloibesice escaped the 

 observation of Rosanoff, and what the latter called cystocarps were only a font 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 tetra spore, 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 par- 

 titions 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 Melobesia 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 Nostochinece, 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 tetra- 

 spores. 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, Bosanoff. (M. membranacea, Aresch., in Agardh's Spec. 

 Alg. ; Harvey, Phyc. Brit., PL 347, in part. — M. farinosa, Kiitz., Spec. 

 Alg.; Le Jolis's Liste des Algues. — M. Lejolisii, Bosanoff, 1. c, p. 62, 

 PI. 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, flattened-convex, orifice ciliated ; tetra- 

 spores 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. (3£. farinosa, Aresch., in Agardh's Spec. Alg., 

 non Le Jolis's Liste des Algues.— M. farinosa and M. vemicata ? Harvey, 

 in part,— M.farinosa } Lam,x., in Bosanoff, 1. c, p. 69, PI. 2, Figs. 2-13.) 



