180 BRITISH SEA-WEEDS. 



Genus LXXX. CYSTOCLONIUM. 



Frond fleshy, taper, much branched, composed of three 

 kinds of cells ; those in the centre cord-like, formed of 

 elongated longitudinal fibres ; the second series large and 

 round ; the external, or bark layer, small and angular. 

 Spores minute, arranged in masses, several of which are 

 enclosed in a thick pericarp, in conceptacles which are partly 

 immersed in the branches; tetraspores zonate, scattered 

 among the external cells of the branches. — Cystoclo- 

 xitjm, from the Greek Jcustis, a bladder, and Moon, a young 

 shoot. 



The present position of this genus is very different 

 from that which it formerly occupied, and has been as- 

 signed to it in consequence of the arrangement of the 

 fructification. The structure of the frond is, however, 

 the character by which the plants composing the genus 

 are distinguished from their immediate allies. 



Cystoclonium purpurascens. The purple Cysto- 

 clonium. 



Frond taper, much branched ; branches alternate, elon- 

 gate ; branchlets numerous, tapering to each end. Spores 

 in conceptacles embedded in the branchlets, either singly or 

 two or more together ; tetraspores zonate, immersed among 

 the surface cells of the branchlets. 



This species is a summer annual, and grows on rocks, 

 etc., between the tide-marks. It is one of the most 

 common of our native sea- weeds, but is best known 

 under its old name of Hypnea. There is one well- 

 marked variety, (3. cirrhosa. It is irregularly branched 

 and variously distorted ; the branches are zig-zag, here 

 and there swollen, their apices are lengthened into 



