THE MAKIXE ALG.E OF NEW ENGLAND. 179 



oblitiuely out wards to form the cortical layer. The incroaso in the hnpctli of tin- frond 

 arijses from the clonj^ation of the central bundle of tilanients. The wliolf plant is 

 covered by a douse cuticle. The conceptacU's arc fonued from the terminal cells of 

 the filaments just mentioned, which cease clon<]jatinjx an<l lose their caUareons incnis- 

 tation, the cuticle also fallin<^ away. The ju'ripheral fdaments, at the same time, 

 continue to clon«;ate and project beyond the central bundle of lUameut«», thus forming 

 the wall of the conceptacle. 



C. OFFICINALIS, L. ; riiyc. Uiit., PI. 22'2. — Common Coralline, 



Dia»cioiis, frouds two to six inches high, arising in dense tufts from a 

 calcareous disk, decompound-pinnate, lower articulations cylindrical, 

 twice as lon^ as broad, upper articulations obconical or pyriforni, sli<]:litly 

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

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



Var. PROFUNDA, Farlow. 



Frouds 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. sqnamata, which is monoecious, 

 and has a lilameutous base, and whose upper articulations are compressed with shaq* 

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

 bo expected with mm. 



:MEL0BESIA, Aresch. 

 (Possibly from fitli^oia or ^7]?.n^noic, the daughter of Oceanus.) 

 Fronds calcareous, horizontally expanded, orbicular, becoming con- 

 fluent and indefinite in outline, conceptacles external or iuimersed; 

 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 McJobinia, Lithophi/Uum, and LUhothamn'um are not 

 well definwl. In M. Thureiii, Bornet, the plant consists merely of a few short lilaments, 

 which are buried in the substance of CoraUina sqnamata and several species of Jania, 

 upon whose surface the concei)tacles of the Mdohinia are alone visible. From this 

 species, in which the frond may be said to ])e rudimentary, w<' pass through forms in 

 which the frond is in the form of calcareous crusts or i)lates till we me«'t heavy, irreg- 

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

 l»aper, Melobtnia, including Lithophyllum of Kosanotf, comjjrehends all the smaller and 

 thinner f«)rms in which the frond does not rise in the form of irregular tubercles or 

 branches, while in Lithothamnion am placed the branching and heavier species, referre<l 

 by the older writers, as Linnjeus, Ellis and Solander, Lamarck, antl others, io Millepora 

 ' T yullipora, and by Kiit/ing to SpnmjUcn. Our common simmIcs, L.poJifmorphum, which 

 liics not often branch, shows the iusuflicient b.asis on which the genera of this group 

 -St. Although there is consitlerable diversity in the structure of the fronds, tho 

 •rgans of fructification, with some slight modilications of the anther<»/.oi<ls and tetra- 

 6pores, arc the same as in CoraUina and Jauia. The most detailed account of the 



