THE SHORES OF BRITAIN. 45 



circumstances connected with the history of the sea- 

 plants is, the beautiful and varied apparatus with 

 which many of them are provided for securing 

 buoyancy. It seems to be essential to their health 

 that they should at least approach the surface, but 

 as their substance is specifically heavier than water, 

 many of them are greatly lengthened, and fur- 

 nished with hollow vessels inflated with air, by 

 which their weight is diminished. These differ 

 much in form and position in the various tribes; 

 in the Sea-wrack (F. v&siculosus), we saw them take 

 the form of bladders, arranged in pairs on each side 

 of the midrib; in the Knotted- wrack (F. nodosus) 

 the stem swells at intervals into hollow bulb-like 

 dilatations, while in the long Sea-lace before us, 

 the same end is answered by dividing the hollow 

 tube into chambers, interrupted at short distances 

 by portions of the solid substance of the frond; 

 the cavities being filled in some unknown manner 

 with air, probably hydrogen generated by the plant 

 itself. ' 



Many of the Algce are rather extensively used as 

 food; and though to one unused to such diet they 

 would in general seem to offer little temptation to 

 the appetite, the poorer natives, not only of our own 

 but of other shores, eat them with much relish. Let 

 us not despise their taste, though differing from our 

 own, but rather adore the beneficence of God, who 

 has supplied in much abundance an additional source 

 of nutriment, and has conferred on the recipients 

 of His bounty the taste requisite for its enjoyment. 

 From the quantity of saccharine matter which tkey 



