242 CERAMIACEiE. v. 



cidly articulate, with thick hyaline cell-walls. Articulations very variable in length 

 in different specimens and in different parts of the same specimen, four to twelve 

 times as long as broad, the upper ones shortest. Branches and ramuli patent, 

 scarcely attenuate, obtuse, in some specimens regularly opposite, in others frequently 

 alternate or secund. Tetraspores almost always pedicellate (terminating depauper- 

 ated ramuli), solitary or clustered, spherical, tripartite, with broad perispores. 

 Colour, a rosy or brownish red. Substance soft. It adheres to paper. 



Our var. /8 closely agrees with specimens of Cal. roseolutn, Ag. communicated to 

 me by Prof. Areschoug ; but I think it also passes insensibly into the Cal. variabile, 

 As. which Prof J. Asardh now agrees with me in uniting to C Turneri. In Prof. 

 Bailey's specimens the ramuli are almost always opposite ; in Dr. Durkee's as con- 

 stantly alternate or secund ; each agrees with a corresponding British form of this 

 variable species. 



Sect. 6. Pusilla : Hoot a small callus. Fro7icls, minute, tufted, irregularly decom- 

 pound, erect, growing on rocks, or parasitical. 



17. Callithamnion Rothii, Lyngb., tufts widely spreading, dense, velvetty ; 

 filaments very slender, short, erect, dichotomous or irregularly branched ; branches 

 long, straight, very erect or appressed ; articulations about twice as long as broad ; 

 tetraspores clustered, borne on short, sub-terminal, corymbose ramuli. J. Ag. Sp. 

 Alg. %p. 17. Kiitz. Sp. Alg.p. 640 Harv. Phyc. Brit. 1. 120. B. Conferva Rothii, 

 Dillw. Conf. t. 73, B. Bot. t. 1702. By ssus purpurea, E. Bot. t. 192. Dilbv. Conf. 

 t. 43. 



Hab. On submarine rocks near high water-mark. Ylalihx, W. H. H. Penobscot 

 Bay, Mr. Hooper. Rhode Island, Prof. Bailey, (v. v.) 



Filaments about a quarter inch in height, spreading in a continuous, velvetty 

 pile, resembling crimson plush, over rocks and stones in patches from a few inches 

 to many feet in extent. The plant is more or less luxuriant as it grows in deep or 

 shallow water. The depauperated state called By ssus purpurea, E. Bot. grows at 

 the extreme limit of the tide, in places where it is merely wet by the spray at high 

 water. 



The American specimens are not in fruit, but in other respects are the same as 

 British ones. 



18. Callithamnion luxurians, J. Ag. ; filaments minute (2 — 3 lines high), 

 excessively branched from the base, sub-dichotomo-multifid or secundly decom- 

 pound ; branches rather patent, very long, attenuated, with secund, whip-like, 

 secondary branches and few ramuli ; articulations four times as long as broad ; 

 tetraspores elliptical, pedicellate, scattered. /. Ag. Sp. Alg. 2, p. 14. Kiitz. Sp. 

 Alg.p. 639. 



