MARINE ALG^ OF BEAUFORT, N. C. . 523 



aa. Thallus consisting of an irregularly spreading, calcareous mass incrusting stones, coral, 



or other algae c 



c. Mature tetrasporangial conceptacle having a separate opening for each sporangium 



-- 3. Lithothamnium (p. 524). 



cc. Mature tetrasporangial conceptacle having a single opening through which all the 



sporangia discharge, vegetative tissues usually in fairly regular layers. .4. Lithophyllum (p. 525). 

 aaa. Thallus erect, segmented, branched j 



d. Cystocarps forming wartlike protuberances, scattered over the surface of the seg- 



ments - 5. Amphiroa (p. 526): 



dd. Cystocarps immersed in the swollen apices of some segments 6. Corallina (p. 527). 



Genus i. Melobesia Lamouroux. 

 Melobesia, Lamouroux, 1816, p. 313. 



Thallus forming a small, flattened disk, attached to the substratum by. the entire 

 under surface, strongly incrusted with lime, composed of a single, undifferentiated 

 stratum, consisting of numerous rows of cells disposed in a radiating, fanlike arrange- 

 ment, with larger, more-elongated cells (so-called "hair cells" or "heterocysts") present 

 among the ordinary cells; tetrasporangia zonately divided, borne in flask -shaped con- 

 ceptacles formed by the separation of thallus cells, these conceptacles borne superficially 

 or somewhat immersed in locally thickened portions, opening to the exterior by a single 

 central pore, or by a separate pore situated above each tetrasporangium ; antheridial 

 and cystocarpic conceptacles flask-shaped, superficial or somewhat immersed, opening 

 by single, central pores. 



About ,20 species, widely distributed, especially in warm seas. 



The group of algae including this and related genera has been differently arranged 

 by different authors and has recently been extensively divided. There is at present 

 little uniformity in the treatment of the forms included in this group, and it seems prob- 

 able that further work will change the arrangement proposed by present authors. 



Melobesia farinosa Lamouroux. 



Melobesia farinosa, Lamouroux, 1816, p. 315. 

 Melobesia farinosa, Farlow, 1882, p. 180. 

 Melobesia farinosa. De Toni. 1905. P- 1764- 

 P. B.-A. Nos. 200, 1549- 



Frond forming small, thin, flat, more or less rounded disks, i to 5 mm. in diameter, surface fari- 

 naceous, irregularly rimose from the center to the periphery, composed of a single stratum except in the 

 vicinity of conceptacles; conceptacles scattered over the frond, o.i to 0.2 mm. in diameter, rather 

 inconspicuous, opening by single central pores surrounded by elongated cells, but not conspicuously 

 bordered by cilia. 



Generally distributed in all seas. 



Abundant on other algae on Bogue Beach, Beaufort, N. C., abundant on Sargassum filipendula 

 dredged from coral reef offshore, July to August, 1915, probably at other times also. 



Forma callithamnioides (Falkenberg) Foslie. Fig. 47. 



Melobesia callithamnioides, Falkenberg, 1879, p. 265. 

 Melobesia callithamnioides, De Toni, 1905, p. 1765. 

 Melobesia farinosa i. callithamnioides, Foslie, 1905, p. 96. 



Fronds very variable, consisting of creeping, closely adherent, dichotomously branched filaments 

 which are sometimes considerably elongated, often spreading out toward the apices and coalescent into 

 more or less dense structures broken by more or less numerous interspaces, sometimes forming more or 

 less complete dichotomously radiating disks, closely adherent by the entire lower surface; conceptacles 

 of the same size as in the species, but rarer, the form being mostly sterile. 



Naples; Adriatic Sea. 



