THE MARINE ALG.E OF NEW ENGLAND. 179 



obliquely outwards to form the cortical layer. The increase in the length of the frond, 

 arises from the elongation of the central bundle of filaments. The whole plant is 

 covered by a dense cuticle. The conceptacles are formed from the terminal cells of 

 the filaments just mentioned, which cease elongating and lose their calcareous incrus- 

 tation, the cuticle also falling away. The peripheral filaments, at the same time, 

 continue to elongate and project beyond the central bundle of filament' 5 , thus forming 

 the wall of the conceptacle. 



0. officinalis, L. ; Phyc. Brit., PI. 222. — Common Coralline. 



Dioecious, fronds two to six inches high, arising in dense tufts from a 

 calcareous disk, decompound-pinnate, lower articulations cylindrical, 

 twice as long as broad, upper articulations obconical or pyriform, slightly 

 compressed, edges obtuse ; conceptacles ovate, borne on the ends of the 

 branches, or some of them hemispherical and sessile on the articulations. 



Var. profunda, Farlow. 



Fronds elongated, with few, irregular branches. 



Common in tide-pools ; the variety in deep water. 



Europe; North Pacific? 



The only species known on our coast, often lining the bottoms of pools, and when 

 exposed to the sun becoming white and bleached. C. squamata, which is monoecious, 

 and has a filamentous base, and whose upper articulations are compressed with sharp 

 edges, especially on the upper side, is a common species of Northern Europe, and may 

 bo expected with us. 



MELOBESIA, Aresch. 



(Possibly from [leAipoia or iirfkofioaLc, the daughter of Oceunus.) 



Fronds calcareous, horizontally expanded, orbicular, becoming con- 

 fluent and indefinite in outline, conceptacles external or immersed; 

 antherozoids spherical, furnished with one or two short projections; 

 tetraspores either two or four parted, borne sometimes in conceptacles 

 having a single orifice, at other times in conceptacles having several 

 orifices. 



The limits of the three genera Melobesia, Litlwplujllum, and Lilhothamnion are not 

 well defined. In M. Tliuretii, Bornet, the plant consists merely of a few short filaments, 

 which are buried in the substance of Corallina squamata and several species of Jania, 

 upon whose surface the conceptacles of the Melobesia are alone visible. From this 

 species, in which the frond may be said to be rudimentary, we pass through forms in 

 which the frond is in the form of calcareous crusts or plates till we meet heavy, irreg- 

 ularly branching forms, which resemble corals much more than plants. In the present 

 paper, Melobesia, including LithopliylUnn of Rosanoff, comprehends all the smaller and 

 thinner forms in which the frond does not rise in the form of irregular tubercies'or 

 branches, while in Hthothamnion are placed the branching and heavier species, referred 

 by the older writers, as Linnaeus, Ellis and Solander, Lamarck, and others, to Millepora 

 or Nullipara, and by Kutzing to Sponyites. Our common species, L.pohjmorphum, which 

 does not often branch, shows the insufficient basis on which the genera of this group 

 rest. Although there is considerable diversity in the structure of the fronds, tho 

 organs of fructification, with some slight modifications of the antherozoids and tetra- 

 spores, are the same as* in Corallina and Jania. The most detailed account of the 



