THE MAKINE ALG^ OF NEW ENGLAND. 135 



tips of tlie branches. The genus has been split up into a number of different genera 

 by Ktttzing, but by most writers his divisions are only accepted as subgenera. Sterile 

 specimens are not easily determined and it is always desirable to have tetrasporic 

 plants. Although we have an abundance of the genus on our coast, the number of 

 species is comparatively small, and the group of species having spines at the nodes is, 

 as far as is known, quite wanting. 



Sect. I. Fronds without spines, cortical cells Recurrent from the nodes mid 

 more or less completely covering the internodes. 



C. rubrum, Ag. (C. rubrum, Phyc. Brit., PI. 181.) 



Fronds robust, dichotoinous, subfastigiate, branches erect, apices in- 

 curved or forcipate, nodes contracted below; tetraspores in irregular 

 series at the nodes, immersed ; favellre lateral, solitary, with a short in- 

 volucre. 



Var. proliferum, Ag. (C. botryocarpum, Phyc. Brit., PI. 215.) 



Pronds beset on all sides with numerous, lateral, simple or forked 

 branchlets. 



Yar. secundatuii, Ag. 



Branchlets generally secund. 



Var. squarrosum, Harv, 



Fronds small, regularly dichotomous, fastigiate, with very few, short, 

 lateral branchlets, lower divisions distant, spreadiug, upper divisions 

 close together, widely spreading, apices often revolute. 



Everywhere common; var. squarrosum on Zostera, Massachusetts Bay. 



A ubiquitous and variable species, of which we have enumerated only the principal 

 forms. The typical form is easily recognized, and the same is true of most of the va- 

 rieties. The var. decurrens has the internodes partly naked, especially in the upper 

 part. The var. decurrens of the Nereis is referred by Agardh to the next species, 

 and is distinguished from the true var. decurrens of C. rubrum, which has immersed 

 tetraspores, by the large tetraspores arranged in a regular circle at the nodes and pro- 

 jecting decidedly above the surface. 



C. CIRCINNATUM, Kiltz. 



Fronds setaceous, dichotomous, fastigiate, divisions erect, patent, 

 apices forcipate, internodes partly corticated by the cells which are de- 

 current from the nodes; tetraspores large, projecting in a riug around 

 the upper nodes. 



Glencove, L. L, Mr. Young / Dartmouth, Mass., Miss Ingraham ; Mag- 

 nolia, Mass., Mrs. Brag. 



Agardh, in his Epicrisis, refers to the present species the C. decurrens of Harvey (Phyc. 

 Brit., PI. 276), which in the Nereis Am. Bor., is made a variety of C. rubrum. There is 

 a var. decurrens of C. rubrum which is admitted by Agardh, which, if we understand 

 correctly, has small immersed tetraspores. This form occurs also with us, but we 

 have no notes as to the locality. To the present species we refer forms in which the 

 upper internodes are scarcely corticated at all and iu which the large, projecting tet- 

 raspores are in a single ring at the upper nodes. 



