390 THE INHABITANTS OF TIIE SEA. 
CHAP. XIX. 
MARINE PLANTS. 
The Alge.—Zostera marina.—The Ulve and Enteromorphe.—The Fuci.—The 
Laminariz.—Macrocystis pyrifera.—Description of the Submarine Thickets at 
Tierra del Fuego.—Nereocystis lutkeana.—The Sargasso Sea.—The Gathering 
of edible Birds’-nests in the marine Caves of Java.—Agar-Agar.—The Floridez. 
—The Diatomacezee—Their importance in the economy of the Seas. 
Tue dry land develops the most exuberant vegetation on the 
lowest grounds, the plains and deep valleys, and the size and 
multiplicity of plants gradually diminish as we ascend the 
higher mountain regions, until at last merely naked or snow- 
covered rocks raise their barren pinnacles to the skies: but the 
contrary takes place in the realms of ocean: for here the greater 
depths are completely denuded of vegetation, and it is only 
within 600 or 800 feet from the surface that the calcareous 
nullipores begin to cover the sea-bottom, as mosses and lichens 
clothe the lofty mountain-tops. Gradually corallines and a 
few algz associate with them, until finally about 80 or 100 
feet from the surface begins the rich vegetable zone which 
encircles the margin of the seas The plants of which it is 
composed do not indeed attain the same high degree of deve- 
lopment as those of the dry land, being deprived of the beauties 
of flower and fruit: but as the earth at different heights and 
latitudes constantly changes her verdant robe, and raises our 
highest admiration by the endless diversity of her ornaments, 
thus also the forms of the sea-plants change, whether we descend 
from the brink of ocean to a greater depth, or wander along the 
coast from one sea to another; and their delicate fronds are as 
remarkable for beauty of colour and elegance of outline, as the 
leaves of terrestrial vegetation. 
The difference of the mediums in which land- and sea-plants 
exist naturally requires a different mode of nourishment, the 
