3<iO THK INHABITANTS OF THE SEA. 



CHAP. XIX. 



i 



MARINE PLANTS. 



The «Ugae. — Zostcra marina.— The Ulvse and Enteromorphae. — The Fuci. — The 

 Laminariae. — 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 Florideae. 

 • — The Diatomaeese — Their importance in the economy of che Seas. 



The 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 algae associate with them, until finally about 80 or 100 

 feet from the surface begins the rich vegetable zone which 

 encircles the margin of the sea. 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 



