236 BRITISH SEA-WEEDS. 



attach themselves by small disc roots to the sea-weed on 

 which the plant is parasitic, growing in tufts one to two 

 inches high, simple, or repeatedly branched ; branches op- 

 posite, sometimes alternate, spreading ; branchlets simple, 

 slender, opposite ; articulations of the stem five to ten 

 times as long as broad, of the branches four to five. 

 Favellse two-lobed, borne on shortened branches, and sur- 

 rounded by involucral branchlets ; tetraspores tripartite, 

 globose, on the sides of short, simple, or branched stalks, 

 which rise from the base of the branchlets. 



This species is common all round our coasts. It 

 grows on Algse in tide-pools in summer, and is annual. 

 Its habit and texture are very different from the allied 

 species, and it may, therefore, be readily recognized. 



Callithamnion barbatum. The bearded Callitham- 

 nion. 



Fronds forming dense intricate tufts, matted together, 

 one to two inches high, much and irregularly branched ; 

 branches alternate or opposite, long, simple, or bearing 

 another series, clothed with minute, spine-like, opposite 

 branchlets, which are distant or absent in the lower part of 

 the branch, but closely and regularly placed near the tip ; 

 articulations twice or thrice as long as broad. Favellse un- 

 known ; tetraspores tripartite, elliptic, with a broad trans- 

 parent margin, borne on the branchlets. 



Mr. Ralfs first gathered this species in 1838, and only 

 one or two specimens have been found since ; I fear, 

 therefore, it must be considered very rare. It is sup- 

 posed to be perennial, and grows on mud-covered rocks 

 in tide-pools. 



