134 KEPORT OF COMMISSIONER OF FISH AND FISHERIES. 



straight or falcate, sharply serrate, especially on the lower side, and the 

 opposing pinna pinnately divided or compound 5 pinn?e nearly at right 

 angles to the axis, apices acute; tetraspores borne in dense ellipsoidal 

 cluster either at the ends of the simple pinnre or on the serrations and 

 tips of the compound pinn?e; tetrasporic masses interspersed with mono- 

 siphonous incurved branches; favell?e in similar position to the tetra- 

 spores, nearly concealed by the large, incurved, usually serrate divisions 

 of the involucre. 



On algse, especially on stems of Laminaria, below low- water mark. 



Common north of Boston ; Thimble Islands, near Xew Haveu, and 

 dredged off Block Island, Prof. Eaton. 



A common and cliaracteristic alga of our nortlieru coast, extending tlirongh Green- 

 land to the northern coast of Europe, and also found in the North Pacific. The i^resent 

 species, together with Euiliora cristata and Delesseria 8inuosa, form the greater part of 

 the specimens collected for ornamental purposes by ladies on the Northern New England 

 coast. P. serrata, when dried, is usually very dark colored, unless it has previously 

 been soaked for some time in fresh water, and it does not adhere well to paper unless 

 under considerable i^ressure. It cannot be mistaken for any other species growing on 

 our coast. Whether it is a variety of F. 2)Jumosa is a question about which writers do 

 not agree, but, although in this connection our form has been kept as a distinct spe- 

 cies, it is highly probal^le that it is really nothing more than a coarser northern form 

 of P. plumosa. The typical form of P. plumosa is certainly unknown in New England. 

 The type is more slender, and the pinnse are pectinate, not serrate. The i^osition of 

 the fruit is the same, the principal difference being in the more strongly marked in- 

 volucre of the favellse and in the tetraspores, which are borne on densely fastigiate 

 branches, which have no cortications, and some of which are inciuwed and project 

 beyond the general sporiferous mass. In P. plumosa tbe tetraspores are also borne on 

 the tips of monosiphonous branches, but they are not densely conglomerate, nor are 

 the projecting incurved ramuli prominent. The present species is very rare south 

 of Cape Cod, being known in only two localities and in a much reduced form. 



CEEAMIUM, Lyngb. 



(From KEpauLov, a small }3itcher.) 



Fronds filiform, dichotomous or occasionally subpinnate, monosipho- 

 nous, composed of a series of large ovate or quadrate cells, with bands of 

 small corticating cells at the nodes, and m some species also extending 

 over the internodesj antheridia forming sessile patches on the upper 

 branches 5 tetraspores tripartite, formed from the corticating cells 5 

 cystocarps (faveUce) sessile at the nodes, usually involucrate. 



A universally diffused and easily recognized genus, of which, however, the species 

 are by no means easily recognized. The genus is distinguished by the monosiphonous, 

 dichotomous frond, with bands of small corticating cells at the nodes, or, in some cases, 

 covering the internodes as well. The tips of the filaments are forked and usually de- 

 cidedly incurved, whence the generic name is derived. The apical growth and forma- 

 tion of the cortex is fully detailed by Na^geli and Cramer in Pflanzeuphysiologische 

 Untersuchugen, Part lY. The procarp in Ceramium is furnished with two trichogynes 

 and a single caiiiogenic cell formed from the cortical cells on the convex side of the 



