V. CERAMIACE^. 213 



articulation or the greater portion of it ; in the second, they are confined to a 

 definite band surrounding the nodes. 



Sect. 1. Rubra; Frond unarmed {not spinuliferous) ; the stratum of cortical cells 

 decurrent from the nodes, and more or less completely clothing the surface of the 

 internode. 



1. CERAinuM nitens, J. Ag. ; frond subsetaceous, slightly attenuated upwards, 

 irregularly dichotomous, diffuse, the branches widely spreading and divaricating ; 

 upper branches zig-zag, with lateral, distant, frequently secund branches and 

 ramuli ; ultimate ramuli scattei'ed, subulate, straight at the point ; internodes 

 clothed with cells on all parts of the frond, the lower ones twice as long as broad, 

 the upper very short. J. Ag. Sp. Alg. 2, p. 130. 



Hab. At Key West, Florida, W. H. H., Prof Tuomey, No. 18, (v. v.) 



Frond four to eight inches long, not so thick as hog's bristle, dichotomously 

 branched from the base, all the divisions very patent, often spreading at right 

 angles, and sometimes with still greater divergence. The upper forks are equally 

 wide with the lower, but are less regular ; one arm of the dichotomy being fre- 

 quently shortened to a branchlet. Thus the ramification becomes as it were alter- 

 nately zig-zag or secund. Eamuli few or many, filiform, simple, acute, not forci- 

 pate at the extremity, distant and very patent. Stibstance rather firm. Colour a 

 full red or brownish. Fniit unknown. Internodes uniformly coated with small 

 cells, not much or at all contracted at the nodes. 



I have not seen specimens of Agardh's plant, and may be wrong in the above 

 reference. But be this as it may, I have no hesitation in regarding the plant here 

 described as a distinctly marked species, difl^ering from C. rubrum not merely in 

 ramification, but essentially in structure. If cross sections of both plants be com- 

 pared together under the microscope, the differences may be readily seen. In our 

 C. nitens the walls of the monosiphonous frond are very thick, and the peripheric 

 cells are set within the pellucid substance of the wall in dichotomous, radiating, 

 horizontal series, whose apices constitute the superficial coating. In C. rubrum the 

 surface cellules are of large size, not disposed in radiating lines, and a circle of 

 empty, polygonal cells surrounds the central tube, as in Microcladia. 



2. Ceramium rubrum. Ag. ; frond robust, setaceous, gradually attenuated, dicho- 

 tomous, sub-fastigiate, with or without lateral simple or forked ramuli ; segments 

 erecto-patent, the apices either slightly incurved or hooked ; lower internodes twice 

 or thrice as long as broad, contracted at the nodes, more or less densely covered 

 with surface cellules ; favellte lateral, subtended by three or four short ramuli ; 

 tetraspores distributed round the nodes. /. Ag. Sp. Alg. 2, p. 127. Kiitz. Sp. Alg. 



