18 BRITISH SEA-WEEDS. 



them in different directions, and exhibit a succession' of 

 the brightest metallic tints of green and blue and purple. 

 Cystoseira ericoides is the most remarkable example of 

 this effect, which is one of its specific characters. The 

 phenomenon ceases directly the plant is drawn from the 

 water, and the collector is aware that it must do so. 

 Nevertheless, he will probably experience a momentary 

 disappointment to find his dusky beauty so suddenly de- 

 spoiled of all her brilliant gems. 



There are various processes, such as the application 

 of heat, steeping in fresh water, etc., by which the 

 natural colour of Sea-weeds may be heightened or 

 changed ; but I only mention them in order to caution 

 my readers that they may be applicable to the produc- 

 tion of artistic effects in Sea-weed pictures, baskets, etc., 

 but should never be used in the preparation of scientific 

 specimens. 



I have alluded to the general distribution of the three 

 classes of Sea-weeds — the Olive-greens on the shore and 

 exposed rocks ; the Reds in deep water or shady pools ; 

 and the Grass-greens near high-tide mark, where they 

 are subject to the action of light, and to contact with 

 fresh water. These are facts which should interest 

 every student of marine botany, whether his collection 

 and researches be general or confined to the plants of 

 any particular locality. The Sea-weeds of our shores 

 are but a part of the large family distributed over all the 

 waters of the globe, of which they are, as it were, an 

 epitome. There is a natural harmony running through 

 the whole, and the same laws, modified, of course, by 

 circumstances, apply to the waters which surround these 

 islands, as to those which beat upon the shores of the 

 Antipodes. 



