CERAMIACE.E. 233 



stems in young plants transparent, becoming opake and 

 veined as they increase in age, much branched ; branches 

 alternate, much divided ; plumules alternate, simply pinnate, 

 with a roundish or ovate outline ; pinnae long, more or less 

 incurved, either quite simple, or furnished with a few pin- 

 nules at the tip; articulations of the stem and branches 

 four or five times as long as broad, somewhat swollen at 

 the joints, those of the plumules becoming gradually shorter. 

 Favellse in clusters, generally terminating short branches ; 

 tetraspores tripartite, borne on the upper side of the pin- 

 nules of the plumules, one at the apex of each of the three 

 or four lower joints. 



This is a very handsome, dark-coloured species, not 

 uncommon in many localities. It grows on rocks and 

 large sea-weeds, near low-water mark, or at the mouths 

 of tidal rivers. It is annual, and matures in summer. 



Section 2. — JFro?ids pinnate, the pinnce opposite. 



Callithamnion fioccosum, Pollexfen's Call!- 

 thamniou. 



Fronds densely tufted, from one to four inches in length, 

 flaccid, irregularly divided in a distantly alternate, forked 

 manner ; branches naked, or clothed at intervals with short, 

 secondary branches ; articulations throughout the frond 

 transparent, from twice to four times as long as broad, each 

 bearing near its apex a pair of short, awl-shaped, spine- 

 like branchlets. Favellse unknown ; tetraspores tripartite, 

 stalked, near the base of the awl-shaped branchlets. 



This is a very rare plant, apparently exclusively con- 

 fined to northern latitudes. The Orkney Islands and 

 Aberdeen are the recorded habitats in this country. 

 It grows on rocks, near low-water mark, in spring, 



