68 



PURPLE LAYER. 



excited by the unwonted light, the plant had 

 poured forth so much oxygen that its entire 

 surface was thickly studded with tiny sparkling 

 beads, that had buoyed up the whole plant, each 

 bubble acting as a miniature balloon. When, 

 however, a black cloud came over the sun, the 

 bubbles soon detached themselves, ascended to 

 the surface, and as there were no more to take 

 their place, down dropped the plant to the 

 bottom. 



On a bright day the little oxygen bubbles 

 are so rapidly exuded, that they quite fill the 

 water, rising to the surface, and there dissipat- 

 ing, very much like the sparkling air-bells in 

 champagne. 



The Purple Laver, as it is called in England, 

 or the Sloke, as it is termed in Ireland, is 

 another of these useful plants. In external ap- 

 pearance it very much resembles the ulva, save 

 that the colour, instead of being light green, is 

 purple. From this peculiarity of colour it is 

 called by botanists, Porphyra, which word signi- 

 fies "purple." There appear to be only two 

 species of this genus belonging to our coasts, 

 the one P. laciniata, and the other F. vulgaris. 

 The former of these plants is engraved in plate a, 

 fig. 4. Only a portion of the frond is given. It 



