RHODOMBLAI l B, 7'.' 



rigid, setaceous, of equal diameter throughout, forming glo- 

 bular, fastigiate tufts, manj times dichotomous; the axils 

 ] iat cut ; articulations shorter than their diameter, multistriate, 

 with a dark central spot 5 Biphons from Bixteen to eighteen, 

 Orev. PL Edin.p.SO&. (Atlas, PL \\\ III. Pig. L27.) 

 Hutchinsia fastigiata, Ag. Ceramium fastigiatum, 'Roth. Con- 

 ferva polymorpha, Linn. Pucus lanosua, Linn. 

 Hob. Parasitical on the littoral Fuci, especially apon /' 

 dosus. PerenniaL Summer and autumn. 

 r. ■ -r<»us nearer to high-water marl than any 



others of the genus, and is generally exposed, for many 

 hours of each fade, to the influence of the air. This expo- 

 sure, and the constant alternation of circumstances, pro- 

 bably influence the colour of its frond, and we accordingly 

 find thai it partakes of fche brown tints of the Fuci among 

 which it grows, almosl to the entire extinction of the red 

 colour proper to the family to which its structure allies it. 

 Besides this difference of colour, it differs from mosi others 

 of its genus in having a cell, containing endochrome, within 

 each articulation of the central or axial tube. 



1 28. parasitica ( The parasitic Polysiphonia) \ filaments Blender, 

 rigid, full-red, alternately branched, distichous ; branches 

 bi-tripinnate j pinnules closely Bet, erecto-patent, alternate, 

 awl-shaped, acute: articulations about a^ long as broad, 

 marked with three or four broad hexagonal oblong cells (or 

 siphons) separated by pellucid Bpaces ; Biphons about eight, 

 surrounding a narrow cavity ; capsules ovate, on Bhorl -t:iik- ; 

 tetraspores immersed in Bwollen pinnules, Qrev. Fl.JSdin.p. 

 309. (Atlas, PI. \\\ III. Pig. 128.) 

 Hutchinsia parasitica, Ag. II. Mostingii, Lyngb. Conferra pa- 

 rasitica, Hud*. 

 Hob. Parasitica] on the larger Alga?, and. much more frequently, 

 on various Bpecies of Melobesia, at the limit of Low-water, 

 and in from four to fifteen fathoms water. 

 / ; lysiphonia parasitica is. \ believe, a much more ge- 

 nerally distributed species on our shores than is commonly 

 supposed; hut owing to its habital it very frequently es- 

 capes detection. Unless it be obtained by dredging, wnich, 

 in favourable localities, is perhaps the mosi certain means 

 of procuring specimens, it can only he had by examining 

 the submersed perpendicular sides of Ledges oi rock, at the 



extreme limit of Low-water. These Ledges are frequently 



d over with a thin spreading Melobesia or with the 

 of Corallina officinalis, on which the Polysiphonia 



