12 INTRODUCTION. 



a stratum of it lately discovered in Easay^ one of the islands 

 of the Hebrides. 



No part of the structure of Sea-weeds has more univer- 

 sally attracted attention,, than the inflated portions of the 

 stem or frond resembhng bladders. These are seen in many 

 native species^ and they are very conspicuous in Fuciis vesi- 

 culosus and Fiicus nodosus. They are called vesicles, and 

 sometimes air-vessels : those on F. nodos2is are verv remark- 

 able, and escape not the attention of children, who value 

 them the more, because they enable them to play off a 

 practical joke on their inland friends who visit the shore, 

 and whom they delight to startle by the explosion which 

 the heated air occasions, when the vesicles are cast into 

 the fire. 



It is generally supposed that the vesicles are intended to 

 give buoyancy to sea-plants, and the wisdom of God is 

 beautifullv manifested in makinsj them at once useful and 

 ornamental. It has been stated that the plants that are 

 furnished with them, cease to float when the vesicles are 

 cut oft'. Mr. Darwin, that remarkably scientific observer 

 and sound reasoner, mentions, in his most interesting 

 Journal of the Voyages of the Beagle, some Alga) that 

 grow on the rocks in the Arctic Seas, which, though of pro- 



