IV. 
FUCACEiE. 
55 
The geographical range of the Order Fucacece is very extensive. The great bulk 
of the species occur within 35° of the equator on either side, within which limits 
also the generic types are most varied. To the north of 35° Sargassa become rare, 
and on the American shore the highest limit attained by any of this genus is in 
Long Island Sound, about 44°. Beyond this limit the genus Fucus becomes the 
prevalent form, and in the extreme north Himantlialia appears. Cystoseira , which 
has many representatives in the south of Europe, four of which extend as far as 
Great Britain, is not found on the eastern shores of America, and but slightly, 
represented on the north western. It forms an intermediate link, in structure and 
distribution, between the tropical and arctic forms of the order. V ery feAV species 
have been traced into the Antarctic Ocean, where the most remarkable form is the 
gigantic Durvillcea , which has a stipe and habit resembling a Laminaria ; or it may 
be likened to a great Palm-leaf. The shores of Australia are peculiarly prolific in 
plants of this order, and the species of that sea are remarkable as well for their 
beauty, as for the large number of generic types which they exhibit. It is on 
those shores that the most fully organised types of the olive-coloured Alga; are met 
with. 
In an economic point of view, the Fucacece take a high place among sea-plants. 
Their ashes contain a large quantity of carbonate of soda, for which the Fuci were 
formerly very much sought after, and even cultivated on some parts of the coasts of 
Scotland where they did not grow naturally ; — rocks being deposited to attract them 
to pebbly or sandy shores. At one time the proprietors of sea-shores on the most barren 
islands of Scotland drew a very large revenue from the sale of the wrack (varec) 
or sea-ware, which was then burned and its ashes sold under the name of Kelp:* 
but improvements in chemistry, by which carbonate of soda is now cheaply obtained 
from other sources, have almost destroyed the kelp trade. These seaweeds are 
now collected chiefly for manure, for which purpose they are often very valuable. 
Iodine is their most remarkable constituent, and is found in their tissues in 
greater quantity than in any other of its known sources. The increasing demand 
for this valuable substance may, therefore, be expected to cause a partial revival of 
the kelp trade. 
The ordinary species, F. vesiculosus , is eagerly eaten in winter by Scotch and 
Norwegian cattle, which regularly come down to the shore to browse on it at 
the recess of the tide ; and Linmeus tells us that in Gothland the peasantry boil 
it, and adding some coarse flour, give it to their hogs. 
SYNOPSIS OF THE NORTH AMERICAN GENERA. 
* Frond branched, leafy. Air-vessels stalked , separate. 
I. Sargassum. Receptacles racemose, in the axils of the upper leaves. 
See Introduction, supra, p. 35. 
