This is one of the most beautiful of the British species of 

 Cystoseira, especially when seen growing under water. It then 

 appears clothed with the richest tints of blue and green, more 

 like those phosphorescent gleams that flash from the lower marine 

 animals than any vegetable colours. As each twig Waves to and 

 fro in the water the hues vary, and sometimes, when the light 

 falls partially on a branch, some portions seem covered with sky- 

 blue flowers, while others remain dark. All these beautiful tints 

 perish when the plant is removed from the water. The specific 

 name ericoides, or heath-like, alludes both to the brilliant colouring 

 and the shrubby character of the frond, which is covered with 

 small ramuli resembling the leaves of a heath. 



C. ericoides is common on the southern shores of our islands, 

 and becomes gradually less frequent towards the north. It has 

 been once found on the coast of Ayrshire by the Rev. D. Lands- 

 borough. 



Fig. 1. Cystoseira ericoides: — of the natural size. 2. Receptacle and vesicle, 

 both formed in the apex of a branch. 3. Section of a conceptacle, showing 

 the spores and antheridia. 4. A spore : — all more or less magnified. 



