180 CALLITHAMNION. 



on age and situation. Colour a full or pale rose-red, given out to fresh 

 water. Some specimens have a very straggling look, the chief divisions 

 being set with irregular ramuli, having something the character of a young 

 plant of C. tetricum, the uppermost branches only having a few plumulate 

 rainuli. On examination of numerous specimens, in different states, and 

 from various localities, I am induced to unite C. seminudum of Agardh 

 and of ' Br. Fl.' with the older species C. Borreri. The chief differences I 

 can find are, that the state called Borreri is more flaccid, of paler colour, 

 more laxly branched, and having rather longer joints ; differences which, 

 in such variable plants, are not of much value. 



20. C. ajfine, Harv. ; much branched; secondary branches 

 of a roundish outline, long, alternately plumulate ; plumules 

 very narrow, linear-clavate, simply pinnate ; pinnae short, 

 erect, increasing in length upwards, attenuate, crowded at 

 top ; articulations of branches 3 or 4 times, of pinnae once 

 and a half as long as broad. Harv. in Hook. Br. FL ii. 

 p. 344. 



Shores of Bute, on Fuci, Dr. Greville. Excessively branched, 2 or 3 

 inches high, bushy; main filaments much divided, set with very numerous, 

 alternate, secondary branches, of a roundish or ovate figure, alternately 

 plumulate ; plumules short, very narrow ; lowermost pinnules distant, short 

 and somewhat spine-like, uppermost elongated and crowded. Colour a 

 deep red. Articulations of the stem four times as long as broad, closely 

 filled with very slender, longitudinal veins. Capsules either in the axils of 

 the pinnae or on the first joint. A doubtful species. 



21. C. tripinnatum, Ag. ; frond distichously branched, 

 capillary, decomposito-pinnate ; plumules elongate, obovate, 

 tripinnate above ; upper pinnae long and pinnulate, lower 

 short or abortive, each pinna having at its axil a minute pin- 

 nule ; pinnules long, setaceous ; articulations of the stem 

 3 4 times, of the pinnae about twice as long as broad ; te- 

 traspores oval, lateral, on the axillary and occasionally on the 

 other pinnules. Harv. Phyc. Brit. t. Ixxvii. 



On rocks, at extreme low-water mark, very rare. Annual. April and 

 May. Roundstone Bay, Mr. M'Calla. Plymouth, Mr. Rohloff. Fila- 

 ments 1 2 inches high, slightly tufted, perfectly distichous, having a cir- 

 cumscribed, fan-like outline, about triply pinnate ; the primary branches 

 or plumules having an obovate outline. These primary branches are bi- 

 pinnate above, and simply pinnate towards the base, but the most striking 

 character is a minute axillary ramulus rising from the first articulation of 

 each pinnule. Colour a fine crimson, and substance delicate, closely ad- 

 hering to paper. This species has much of the aspect of the following, 

 but in its microscopic characters is nearer to C. Borreri. 



22. C. gracillimum, Ag. ; frond distichously branched, fan- 

 shaped ; filaments capillary, decomposito-pinnate ; upper 

 plumules long, narrow-ovate or lanceolate, patent, bi-tripin- 



