han that of the atmosphere, and consequently the dispersion of species
from one zone to another being less frequently checked by the
intervention of uncongenial climates. The proportion also of land to sea
throughout the globe being small, the migration of marine plants is not
so often stopped by barriers of land, as is that of the terrestrial
species by the ocean. The number of hydrophytes, as they are termed, is
very considerable, and their stations are found to be infinitely more
varied than could have been anticipated; for while some plants are
covered and uncovered daily by the tide, others live at the depth of
several hundred feet. Among the known provinces of Algae, we may mention,
1st, The north circumpolar, from lat 60 degrees N. to the pole; 2dly,
The North Atlantic or the region of Fucus proper and Delesseriae,
extending from lat. 40 degrees N. to lat. 60 degrees N.; 3dly, That of
the Mediterranean, which may be regarded as a sub-region of the _fourth_
or warmer temperate zone of the Atlantic, between lat. 23 degrees N. and
lat. 40 degrees N.; 5thly, The Tropical Atlantic, in which Sargassum,
Rhodomelia, Corallinea, and Siphonia abound; 6thly, The South Atlantic,
where the Fucus reappears; 7thly, The Antarctic American, comprehending
from Chili to Cape Horn, the Falkland Islands, and thence round the
world south of latitude 50 degrees S.; 8thly, The Australian and New
Zealand, which is very peculiar, being characterized, among other
generic forms, by Cystoseiriae and Fuceae; 9thly, The Indian Ocean and
Red Sea; and, 10thly, The Chinese and Japanese seas.[851] In addition to
the above provinces, there are several others not yet well determined in
the Pacific Ocean and elsewhere. There are, however, many species which
range through several of these geographical regions of subaqueous
vegetation, being common to very remote countries; as, for example, to
the coasts of

Europe and the United States, and others, to Cape Horn and Van Diemen's
Land, the same plants extending also for the most part to the New
Zealand sea. Of the _species_ strictly antarctic (excluding the New
Zealand and Tasmanian groups) Dr. Hooker has identified not less than a
fifth part of the whole with British Algae! Yet is there a much smaller
proportion of cosmopolite species among the Algae than among the
terrestrial cellular plants, such as lichens, mosses, and Hepaticae.

It must always be borne in mind, that the distinctness alluded to
be