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 (7 vesiculosus), 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 Alge 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 nutrinient, and has conferred on the recipients 
of His bounty the taste requisite for its enjoyment. 
From the quantity of saccharine matter which they 
