V. CERAMIACE^. 237 



pound ; the lesser and ultimate divisions dichotomously multifid and fastigiate ; 

 articulations of the branches six or eight times as long as broad, of the ramuli 

 shorter; tetraspores solitary on the ramuli, tripartite. /. Ag. Sp. Alg. 2, p. 41. 

 Han. Phyc. Brit. t. 27'2. PhlebotJiamnion corymhosnm, Kiltz. Sp. Alg. p. 657. Con- 

 ferva corymbosa, E. Bot. t. 2352. Var. /3 secundatum ; lesser branches very fre- 

 quently secund, less compound than usual, and the ultimate ramuli very irregular, 

 scarcely corymbose. 



Hab. Frequently growing on Zostera. Halifax, TI". H. H. Boston Bay in seve- 

 ral places, Dr. Durkee, Mrs. Mudge, Capt. Pike, &c. New London, Miss French, 

 Mr. Congdon. Providence, Prof. J. W. Bailey. /3, Massachusetts Bay, Mrs. Mudge. 

 Greenport, 3£r. Hooper, (v. v.) 



Fronds either densely tufted, as is often the case when growing on the leaves of 

 Zostera, or solitary, as sometimes occurs in rockpools or on a sandy bottom. Stems 

 as thick as hog's bristle at the base, soon divided, and then alternately decompound. 

 The larger branches are setaceous below, attenuated upwards, and at length reduced, 

 near the summit, to a cobwebby fineness ; they are very much branched, the primary 

 divisions between alternately pinnate and dichotomous, the secondary and tertiary 

 somewhat zig-zag and set with alternate or secund, dichotomo-multifid branchlets. 

 These dichotomous branchlets are usually fastigiate or level-topped ; the ends, owing 

 to the crowded ramuli, looking dark when displayed on paper, and resembling so 

 many little corymbs ; whence the specific name. The articulations are visible to 

 the base of the stem ; those in the lower part are short, sometimes a little veiny, 

 thick-walled, with a slender tube ; those of the middle and upper portions are very 

 long. The tetraspores are always solitary, scattered on the upper ramuli, being 

 formed out of a suppressed arm of a furcellation. Favellce, binate. Substance, some- 

 what gelatinous. Colour, a beautiful rosy red, rapidly given out in fresh water. 



10. Callithamnion seirospermuvi, Griff. ; fronds solitary or somewhat tufted ; 

 stem setaceous, veiny, gradually attenuated upwards, undivided, set with alternate, 

 lateral, setaceo-capillary, veiny, undivided branches, which are clothed Avith lateral, 

 spirally inserted, dichotomo-multifid, secondary branchlets ; articulations of the 

 stem and branches opaque, of the lesser branches and ramuli pellucid, three to four 

 times as long as broad ; the ultimate ramuli frequently converted into bead-like 

 strings of seirospores. Ham. 3 fan. Ed. l,]x 113. /. Ag. Sp. Alg. 2, p. 42. Phlebo- 

 thamnion seirospei^mum, Kiltz. Sp. Alg. 2, p. 657. Seirospora Grijfithsiana, Harv. 

 Phyc. Brit. t. 2\. Cal. versicolor, var. seirospermum, Harv. in Hook. Joam, Bot. 1, 

 p. 302. 



Hab. Salem, Massachusetts, Mr. J. Hooper. New Bedford, Dr. Roche. Nan- 

 tucket, Dr. Durkee. Shores of Rhode Island, Prof J. W. Bailey, (v. v.) 



Stem, three to five inches high, as thick as hog's bristle below, capillary above, 



