496 BULLETIN OF THE BUREAU OF FISHERIES. 



Froiid flat, thin-membranaceous, i to n cm. wide, 6 to 45 cm. long, usually unbranched, supported 

 on a short stalk continuous with the midrib, tapering at each end; tetrasporangial sori appearing as 

 minute dots scattered over the surface, antheridia as small, whitish spots scattered over the frond, 

 cystocarps as evident dots larger and more conspicuous than the tetrasporangial ones; tetrasporangia, 

 antheridia, and cystocarps borne on different plants; color light to dark rosy pink, sometimes purplish. 



New England to West Indies. 



Fairly abundant throughout harbor and on jetties, Beaufort, N. C., 10 to 30 cm. below low water, 

 December to May, small specimens occasional on Fort Macon jetties during summer and autumn, small 

 specimens on coral reef offshore, May, 1907, and August, 1914; few specimens i cm. tall or less, in 

 sound, Pawleys Island near Georgetown, S. C., August, 1909. 



Family 4. RHODOMELACE/E (Reichenbach) Harvey. 



Frond terete or flattened, usually richly laterally or dichotomously branched, erect 

 or horizontal, structure usually radial, sometimes dorsiventral, cellular, sometimes 

 cellular-filamentous, usually with a conspicuously polysiphonous axis composed of a 

 segmented central axis surrounded by one or more circles of large pericentral cells of 

 equal length, sometimes covered by one or more layers of small cortical cells, apical cell 

 segmented transversely or obliquely (in one subfamily, Laurenciae, approaching the 

 tetrahedral type) the thallus bearing more or less numerous, persistent or evanescent, 

 usually much branched, monosiphonous filamentous lateral outgrowths (trichoblasts) ; 

 tetrasporangia numerous, arising from pericentral cells, embedded in the thallus, covered 

 by special cover cells, scattered over the unaltered smaller branches or in altered branches 

 (stichidia), triangularly divided; antheridia borne on trichoblasts, sometimes apparently 

 on a polysiphonous branch, occurring as small compact bodies of various forms, oval to 

 long cylindrical, terete or flattened, bearing a layer of spermatangia over all or nearly 

 all the surface; carpogonia situated on trichoblasts, sometimes apparently on a poly- 

 siphonous branch, closely associated with cells which, after fertilization, produce the 

 auxiliary cells, forming definite procarps sooner or later inclosed by sterile outgrowths 

 from the thallus ; cystocarps external, conspicuous, secondarily situated on polysiphonous 

 branches, sessile or borne on short stalks, oval or urceolate, pericarp thick, opening by 

 an apical pore, gonimoblast arising from the basal placenta, consisting of a compressed, 

 more or less compact tuft of richly branched filaments, whose apical cells usually produce 

 single, large, oval, or club-shaped carpospores, but in one subfamily, Dasyeae, form small 

 cylindrical carpospores in short chains, the spores, in the former case, having the appear- 

 ance of arising singly on short stalks from the base. 



The largest family of the Rhodophyceae,. containing about 600 species, occurring in 

 all seas, especially in the temperate regions of the Southern Hemisphere. 



KEY TO GENERA. 



o. Growth of thallus sympodial, structure radial, with five pericentral cells, tetrasporangia 



not completely embedded in the stichidia, branching radial * 7. Dasya (p. 508). 



oo. Growth of thallus monopodial b. 



6. Thallus with dorsiventral structure, creeping, bearing elongated, alternate, lateral, 

 creeping branches at regular intervals, and short, erect branches between these, 



tetrasporangia occurring singly 6. Herposiphonia (p. 507). 



66. Thallus usually with radial structure, erect throughout or with conspicuous erect 



branches from an inconspicuous creeping base c. 



c. Polysiphonous axis not evident, thallus composed of large cells not arranged in 

 circles, apical cell divided somewhat tetrahedrally, tetrasporangia situated with- 

 out apparent relation to a pericentral cell i. Laurencia (p. 497). 



