92 MARINE ALG^E 



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 pinnulae, 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. detisa. 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 pinnulse alternating with smaller feather-like pinnulse, 

 giving a dense edge to all parts of the frond. It is found on the Cali- 

 fornia coast. (Plate XXXIII.) 



P. hypnoides. Flat, cartilaginous main stem, much branched, and 

 all beset with pinnulse. It differs from P. densa in having the alternate 

 pinnulae straight and club-shaped, instead of toothed and curved, and 

 the plant is not so dense and compact. Found on the California coast. 

 (Plate XXXIII.) 



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- 



