^S. filamentosa.^ Fronds four to eight inches long; filaments as thick as bristles, irregularly and repeatedly branched; young branches show articulations and seem to be striped; all branches clothed with short, very delicate, transparent filaments, which give the plant a hazy appearance; color purplish-red, which becomes brown when dried; does not collapse when taken from the water. It grows in tufts below low-water mark, and is found in the drift on the beach from Cape Cod southward. (Plate XXXIII.)
The pitcher-weed. This genus is easily recognized by the ends of the filaments, which are forked and incurved, resembling minute pincers or claws. The filaments are also more or less distinctly banded. It is widely distributed.
[Illustration: PLATE XXXI. Callithamnion americanum, a piece magnified. Callithamnion seirospermum. Callithamnion byssoideum, var. fastigiatum. Callithamnion floccosum.]
[Illustration: PLATE XXXII. Griffithsia Bornetiana. Ptilota serrata. Ptilota serrata, magnified. Ptilota elegans.]
[Illustration: PLATE XXXIII. Ptilota densa. Ptilota hypnoides. Ptilota hypnoides, magnified. Spyridia filamentosa.]
^C. rubrum^, red ceramium. This is a very common and robust species, found everywhere, and growing on everything. It is variable in appearance, becoming quite coarse when old, the incurving, claw-like ends, which are characteristic of the genus, being less pronounced. It branches by repeated forking, and, under the microscope, shows a bark-like [pg093] layer of cells over the whole surface, which make the ring-like bands on the filaments less conspicuous.
[Illustration: PLATE XXXIV. Ceramium rubrum, var. proliferum. Ceramium rubrum, top of frond magnified. Ceramium diaphanum. Ceramium tenuissimum, var. patentissimum.]
Variety ^proliferum^. Fronds beset on all sides with simple or forked branchlets. (Plate XXXIV.)
Variety ^secundatum^. Branchlets generally arranged on one side of the filaments, or secund.
^C. strictum^ ("straight"). Brown or purplish-red filaments of hair-like fineness, growing in tufts two to six inches high, branching in narrow forks more and more closely as they reach the top of the frond. There are no principal branches, the filaments being of about the same diameter and regularly dividing in a forking manner throughout. The filaments are banded, the red rings being relatively very narrow. The white interstices at the base are several times longer than broad, but shorten gradually until at the top they are of equal length with the red bands. This species is common from Cape Cod to New York.