IV. 
INTRODUCTION. 
31 
USES OF THE ALGiE. 
The uses of the Algol may he considered under two points of view, namely, the 
general office which this great class of plants, as a class, discharges in the economy 
of nature ; and those minor useful applications of separate species which man 
selects on discovering that they can yield materials to supply his various wants. 
The part committed to the Algol in the household of nature, though humble 
when we regard them as the lowest organic members in that great, family, is not 
only highly important to the general welfare of the organic world, but, indeed, 
indispensable. This we shall at once admit, when we reflect on the vast prepon- 
derance of the ocean over the land on the surface of the earth, and bear in mind 
that almost the whole submarine vegetation consists of Algie. The number of 
species of marine plants which are not Algie proper is extremely small. These on 
the American coast are limited to less than half a dozen, only one of which, the 
common Eel Grass (Zostera marina ), is extensively dispersed. 
All other marine plants are referable to Algie ; the wide spread sea would there- 
fore be nearly destitute of vegetable life were it not for their existence. Almost 
every shore — where shifting sands do not forbid their growth — is now clothed with 
a varied band of Algie of the larger kinds ; and microscopic species of these vege- 
tables ( Diatomacece j teem in countless myriads at depths of the ocean as great as 
the plummet has yet sounded, and where no other vegetable life exists. It is not, 
therefore, speaking too broadly to say that the sea, in every climate and at all 
known depths, is tenanted by these vegetables under one phase or other. 
The sea, too, teems with animal life, — that “ great and wide sea, wherein are 
things creeping innumerable, both small and great beasts,” affords scope to hordes 
of animals, from the “ Leviathan” whale to the microscopic polype, transparent as 
the water in which he swims, and only seen by the light of the phosphoric gleam 
which he emits. Now this exuberant animal creation could not be maintained 
without a vegetable substructure. It is one of the laws of nature that animals 
shall feed on organized matter, and vegetables on unorganised. For the support 
of animal life, therefore, we require vegetables to change the mineral constituents 
of the surrounding media into suitable nutriment. 
In the sea this office of vegetation is almost exclusively committed to the Algce, 
and we may judge of the completeness with which they execute their mission by 
the fecundity of the animal world which depends upon them. Not that I would 
assert that all, or nearly all, the marine animals are directly dependant on the Algie 
for their food ; for the reverse is notoriously the case. But in every class we find 
species which derive the whole or a part of their nourishment from the Algse, 
and there are myriads of the lower in organization which do depend upon them 
altogether. 
Among the higher orders of AlgEe feeders I may mention the Turtles, whose green 
fat , so prized by aldermanic palate, may possibly be coloured by the unctuous green 
juices of the Caulerpce on which they browse. But without further notice of those 
that directly depend on the Algas, it is manifest that all must ultimately, though 
