CALLITHAMNION. 171 



Landsborough ; Kirkwall Bay, Rev. J. H. Pollexfen. — Stem 2 or 6 inches 

 high, setaceous, generally undivided, more or less opake and veiny, set 

 with numerous, sub-distichous, long', simple, alternate, patent branches, 

 the lowest of which are longest, giving the plant, when displayed, a 

 broadly-ovate outline ; the largest frequently bearing a secoad set of simi- 

 lar branches. All are more or less furnished with sub-dichotomo-multifid, 

 level-topped ramuli, of a narrow obovate outline. Tetraspores globose, in 

 beaded strings at the tips of the branchlets, several strings generally tufted 

 at each tip. This beautiful plant has the aspect, and many of the micro- 

 scopic characters of strong specimens of Cal. conjmbosum, but is at once dis- 

 tinguished by the fructification ; the tetraspores in Seirospora being formed 

 out of the terminal ramuli themselves, the whole ramulus becoming con- 

 verted into a string of bead-like tetraspores. 



VIII. Callithamnion. Lyugb. [Plate 23, A.] 



Frond rosy or brownish red, filamentous; stem either 

 opake and cellular, or translucent and jointed ; branches 

 jointed, one-tubed, mostly pinnate (rarely dichotomous or ir- 

 regular) ; dissepiments hyaline. Fructijicalion : 1, round- 

 ish or lobed, berry-like receptacles ffavellccj seated on the 

 main branches, and containing numerous, angular spores : 

 2, external tetraspores, scattered along the ultimate branch- 

 lets or borne on little stalks. — Name, from Ka.'KKo(;, beautiful ^ 

 and ^oi.(Mi.ov^ a little shrub. 



Section 1. Cruciata : ramuli opposite. (Sp. 1 — 7). 



1. C plumula,JL\\\&; stems distichously branched, sub- 

 dichotomous, articulated; each joint bearing a pair of short, 

 recurved plumules pectinated on their upper margin. Hook. 

 Br. Fl. ii. p. 339 ; fVi/att, Ale/. Damn. No. 138 ; Harv. Phyc. 

 Brit. t. ccxlii. Co7if. plumula, Dillw. t. 50. C. Turneri, E. 

 Bot. t. 1637, [not t. 2336).— /3. smaller in every part. 



In the sea from Orkney to Devon, not uncommon. /3. Devonshire, 

 Mrs. Griffiths. Dublin Bay. — Fronds 2 — 5 inches long, distichously 

 branched ; the branches alternate or irregular, the upper ones longest and 

 most divided, slender, articulated throughout ; every articulation having a 

 pair of opposite, horizontal or recurved ramuli, from a quarter to half a 

 line in length, and about a quarter the diameter of the stem, whose upper 

 margin is pectinated with a second series of subulate branchlets, which, in 

 luxuriant specimens, are often again and again pectinated along their inner 

 faces. Tetraspores minute, spherical, borne on the tips of the abbreviated 

 pectinate ramuli. Favellce large, lobed, dark red, on the main branches. 

 Joints of the stem 3 or 4 times longer than broad, of the ramuli shorter. 

 Colour a fine rose-red. Substance flaccid and tender. 



C. cruciatiim, Ag. ; irregularly divided,; branches linear, 



