84 COMMON SEAWEEDS. 



Callith amnion Hookeri. — This was discovered 

 by Dr. Hooker, and is now found dispersed along the 

 British shores from Orkney to Cornwall, and in Ire- 

 land, also in the Channel Islands. 



It grows on coarser seaweed and on sandy rocks. 

 A variable species, yet not difficult to understand if 

 we keep a few leading features in view, such as — An 

 opaque stem and branches, short joints, very distinct 

 branches which have ramuli right and left, which 

 ramuli are again branched or pinnated at every joint ; 

 tetraspores seated on the pinnce. Colour varies from 

 full purple to brownish-red, sometimes pale pink, and 

 fading rapidly in fresh water to dirty white ; there- 

 fore keep it in sea water, or put salt in the water you 

 use to cleanse it before mounting. It is not often more 

 than three inches high. 



Callithamniost Abbusctjla (Bushy Callitham- 

 nion). — Look for this on rocks or mussel shells left 

 bare by the tide at lowest ebb. It is of deep brownish- 

 red colour, much, tufted, matted, the stem stout and 

 full of red veins, branched alternately, and their ramuli 

 branched again, and set with tetraspores. The lesser 

 branches are often decidedly forked, and the favellcB 

 are clustered in three berries on the ramuli. "When 

 dry this often has a greenish hue, and looks well on 

 paper with careful arrangement and thinning out of 

 the branches. Common on the south coast and Chan- 

 nel Islands. 



Callithamnion G-eacillimtjm (" Tern-leaved" 



Callithamnion) . — So named by one of the most intel- 



