92 MARINE ALGA 
Genus Ptilota 
Feather-weed. 
P. serrata. Fronds three to six inches long, dark red in color, 
cartilaginous; flattened main stem with opposite, flattened branches, 
one of which is minute, so that it appears like alternate branching ; 
branches also have lateral branchlets and pinnule, looking like feathers 
or ferns; all branching in one plane, making a flat frond. It is found 
in the drift on the beach after a storm, and is common from Cape Cod 
northward, and also on the California coast. (Plate XXXII.) 
P. elegans. Narrower and more delicate than P. serrata, otherwise 
it has the same essential features. It is common in summer from New 
York northward, growing on cliffs, under Fucus, near low-water mark, 
and it is also found washed upon the beach. (Plate XXXII.) 
P. densa. Frond three to twelve inches high, one eighth of an inch 
wide, flat, cartilaginous ; -has leading stem with flat alternate branches ; 
branches simple or branched again; edges of whole plant beset with 
notched, curved pinnule alternating with smaller feather-like pinnule, 
giving a dense edge to all parts of the frond. It is found on the Cali- 
fornia coast. (Plate XX XIII.) 
P. hypnoides. Fiat, cartilaginous main stem, much branched, and 
all beset with pinnule. It differs from P. densain having the alternate 
pinnule straight and club-shaped, instead of toothed and curved, and 
the plant is not so dense and compact. Found on the California coast. 
(Plate XX XIII.) 
Genus Spyridia 
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 ap- 
pearance; 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.) 
GENUS Ceramium 
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. 
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- 
