CHAPTER XIX.
MARINE PLANTS.
The Algæ.--Zostera marina.--The Ulvæ and Enteromorphæ.--The Fuci. --The Laminariæ.--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 Florideæ.--The Diatomaceæ.--Their importance in the economy of the Seas 390