Ser. RHODOSPERMEZ. Fam. Ceramiee. 
Puate XXI. 
SEIROSPORA GRIFFITHSIANA, Zar. 
Gen. Cuan. Frond rosy, filamentous; stem articulated, one-tubed, the 
articulations traversed by jomted filaments; dranches jomted, one- 
tubed. Fruit: oval tetraspores disposed in terminal, moniliform strings. 
Favelle?. Szrrospora—from ceipd, a chain, and onépos, a seed ; chain- 
seed. 
Serrospora Grifithsiana. 
CALLITHAMNION seirospermum, Griff. in Harv. Man. p. 113. 
CALLITHAMNION versicolor, 8. seirospermum, Harv. in Hook. Journ. Bot. vol. i. 
p- 302. Harv. in Mack. Fl. Hib. part 3. p. 216. Wyatt, Alg. Danm. no.19. 
Has. On rocks and stones in the sea, in four to six fathoms water. Rare. 
Annual. Summer. At Torquay, Mrs. Griffiths. Salcombe, Mrs. 
Wyatt. Portaferry, Mr. W. Thompson. Arran, Rev. D. Lands- 
borough. 
Geoer. Distr. British Islands, rare. Sweden, Areschoug. 
Descr. Root a small disc: Stems solitary or slightly tufted, 1-3 inches high, 
setaceous, generally undivided, more or less opake and veiny ; the veins, which 
are internal, articulated fibres, originating at the insertion of the branches, 
and traversing the stem in a downward, root-like direction. Branches 
tetrastichous or sub-distichous, numerous, long, simple, alternate, patent, 
issuing along the length of the stem from a short distance above the base 
to the apex, closely set; the lowest longest, the upper gradually shorter ; so 
that the general outline of the frond is triangular ovate. The larger branches 
often bear a second set of similar branches. All are more or less furnished 
with sub-dichotomous, multifid, level-topped ramuli, with a narrow-obovate 
outline, jointed, the joints 2—4 times longer than broad, somewhat swollen 
upwards. The ¢e¢raspores are elliptical, triangularly divided, arranged in 
beaded, dichotomous strings at the tips of the branches; that is to say, 
speaking morphologically, the articulations of the terminal ramuli are trans- 
formed into tetraspores. Colour a fine rosy red. Substance gelatinous, 
flaccid, and closely adhering to paper. 
This beautiful plant was discovered by Mrs. Griffiths in the 
Autumn of 1833, and by that acute observer was at once pro- 
nounced to be a new species. I was not so confident of its 
claims to this distinction, and first described it as a variety of 
Callithamnion versicolor, chiefly remarkable for a curious modifi- 
cation of fruit. There is, indeed, a close resemblance to strong 
growing plants of C. versicolor, so close that we are driven to look 
