382 POPULAR FIELD BOTANY. 
are often passed over as of little importance; but many are 
distinguished for their beauty as well as their utility. Algee 
exist in all parts of the ocean; but they vary in different 
regions. They are in general attached to various substances, 
such as stone, rocks, shells, &c., though some are always 
free and floating. The usual colour is olive-brown, or 
green; but many are of a brilliant red, and others nearly 
black. They differ as much in size as terrestial plants, 
some attaining a great length. The Chorda filum, found 
in bays of the Orkney Islands, is occasionally thirty or 
forty feet long, often impeding the passage of the fisher- 
men’s boats. An American species has been procured, 
which measured a thousand or fifteen hundred feet. They 
must grow with great rapidity; for rocks that have been 
completely cleared are found again covered in six monthis, 
and some of the specimens had grown six feet long during 
that period. 
From several species of Sea-weeds Kelp is derived, which 
is of such use in the manufacture of glass and soap. They 
are reduced to ashes by burning, and this formerly gave to 
very many poor people an employment, which was the 
principal means of support in the Hebrides; but lately a 
superior kind, procured from a plant growing on the coast, 
