112 SYNOPSIS OF BRITISH SEAWEEDS, 



founded by Bishop Agardh on a Mediterranean species, 

 which agrees in its fructification with our W. multifida^ but 

 which lias an inarticulate, or rather an opaque, internally 

 jointed Btem. The structure of the favellae and the dis- 

 : ion of the tetraspores are different from what occur 

 in GrrMtksia, and the branching of the frond is more pin- 

 nate than dichotomous. Some fine of Wra/ngelia 

 are found in Tasmania and New Holland. 



LXXXVI. SEIROSPORA. 



218. Griffithsiana {Mrs, Griffiths'^ Seirospora) ; frond n 



filamentous; stem articulated, one-tubed, the articulations 

 traversed by jointed filaments ; branches jointed, one-tub d ; 

 fruit, oval tetraspores disposed in terminal, moniliform 

 strings; iavelke ? — Hare. Phyc. Brit. pi. 21. (Atlas, 

 PL LIT. Fig. 219.) 

 Callithamnion seirospermum, Griff. C. versicolor, var., Harv. 

 Hob. On rocks and stones in the sea, in four to six fathoms 

 water. Rare. Annual. Summer. 

 This beautiful plant was discovered by Mrs. Griffiths in 

 the autumn of 1833, aud by that acute observer was at 

 once pronounced to be a new species. I was not so confi- 

 dent of its claims to this distinction, and first described it 

 as a variety of Callithamnion versicolor, chiefly remarkable 

 for a curious modification of fruit. There is indeed a close 

 resemblance to strong growing plants of C. versicolor, 

 so close that we are driven to look to the fructification for 

 marks of difference. Here however the characters are so 

 broadly defined, that if we regard the fruit of our Seiro- 

 spora as being normal, according to the view first taken 

 by Mrs. Griffiths, and latterly, though with some hesita- 

 tion and reluctance, adopted by me, we are compelled to 

 form a new genus for its reception. In Callithamnion 

 the tetraspores are borne laterally along the ramuli ; here 

 the ramuli themselves are converted at maturity into 

 strings of tetraspores, a tetraspore being formed within 

 each of the articulations of the ramulus. 



LXXXYII. CALLITHAMNION. 



249. Plumula {The little feather Callithamnion) • stems disti- 

 chously branched, subdichotomous, articulated; each arti- 

 culation bearing a pair of short, recurved plumules, pecti- 

 nated on their upper margin, Lyngb. liyd. Dan. p. 127. 

 (Atlas, PL LY. Fig. 251.) 



