122 Rhodora [June 



the branches more slender, beset at the tips with long, secund, atten- 

 uate, acute branchlets, 40-60 fx diam., cells 3-5 diam. 



It is very difficult to give a description of this species that will 

 enable a stranger to recognize it, and yet, in its typical form, it is 

 fairly distinct. It is very variable, passing into C. Jfexuosa, C. hirta 

 and C. laetcvhens. In its typical form it has not the uniformly rlexu- 

 ous filaments of the first, the abundant short ramuli of the second, 

 nor the stout fastigiate ramuli of the third ; but forms partaking in 

 greater or less degree of all these characters are only too common. 

 North of Cape Cod the prevailing form is elongated, with very erect 

 branches ; this form is occasionally found south of Cape Cod, but the 

 more common form has more patent branching, giving quite a differ- 

 ent aspect, though there are no technical distinctions. Farlow's 

 description in the N. E. Marine Algae fits best with the southern 

 form, as does also No. 209, Alg. Am.-Bor. Exsicc, quoted above; this 

 southern form is nearer C. flexuosa than the northern form. No. 

 206 of the same is quite typical C. flexnosa\ No. 724 of Phyc. Bor.- 

 Am. is between the two, but should be ranged under C. Jiexuosa 

 rather than, as distributed, under C. gracilis. 



It is a summer and autumn plant, preferring sheltered places, 

 sometimes occurring in large quantity in muddy bays and harbors, 

 and it is found all along our coast. One form and two varieties can 

 be distinguished by name. 

 C. gracilis forma elongata Collins. 



Collins, Holden & Setchell, Phyc. Bor.-Am., No. 725. 



Fronds attached, with few and erect branches, stretching out on 

 the surface of the water for a meter or more ; color very glaucous 

 green. 



An extreme development of the ordinary northern form, apparently 

 conditioned by its location, shallow warm water pools, on islands in 

 Penobscot Bay, Maine. 

 C. gracilis var. expansa Farlow. 



Farlow, N. E. Marine Algae, p. 55. 



Frond soon detached, forming loose floating masses, irregularly 

 branched. 



With the habit of C. expansa, but not forming a dense felt, Moating 

 loosely in the water of tide pools etc. ; Gloucester, Nahant, Mass., W. 

 G. Farlow; Cape Rosier, Maine, F. S. Collins. 



C. gracilis var. vadorum (Aresch.) 



C. gracilis var. tenuis Thuret in Le Jolis, Alg. Mar. Cherb., p. 61. 



Farlow, N. E. Marine Algae, p. 55. 



Conferva vadorum Areschoug, Alg. Exsicc, No. 19. 



Filaments slender, 40-100 fi, branches few, articulations 4-8 diam. 



Forming indefinite masses below low water mark, Gloucester, 

 Mass., Farlow; Atlantic City, N. J., S. R. Morse. 



Areschoug's name having been published in 1840, it would seem 



