Page:Popular Science Monthly Volume 47.djvu/821

Rh surface of the water. There it unfolds itself in the full light, and finally lies flat on the water, protected against the wet by a fine, bright coating of wax. It is wonderful how large masses of organized material a water plant can lay up with the help of these floating leaves. The great Victoria Regia grows to its full size in a single year from a small seed. Nearly its whole mass is prepared during growth in the leaves, which can perform such a work only in the strong light and the warmth of the tropical zone.

Submerged plants, as we have already said, are less well provided as to the reception of light than those with floating leaves. Hence those are chiefly small forms which we find at the bottom of our waters. Of these the Algæ are the most numerous. There are, indeed, on the whole earth no wet, only moderately light places where Algæ have not established a home. Insensible in a high degree alike to heat and cold, they are capable of growing on the snow of the Alps and on the edges of hot springs. We find them on the stones of rushing mountain torrents, in the plunge of the steepest waterfalls, and in the surf of the seacoast, and again at the bottom of the nearly motionless waters of ditches and ponds. The diversity of their habitats corresponds with the immense multitude of their forms. In the form of microscopic dots they will gradually change all the water of a pond or lake into a disagreeable turbid, green, often rank-smelling fluid; sometimes floating on its surface as green or yellow wads dotted with air bubbles; sometimes they appear at the bottom of the water as thick, roundish bundles of green, tangled threads; sometimes as slippery brown coatings.

The Algæ, of the sea, or seaweeds, are strikingly rich in coloring. Besides green, there are in the sea black, brown, and red forms, the last, under favorable conditions of light, often attaining great size. They seem to be adapted by their peculiar coloring to the tempered blue light of the deeper strata of water. In the great deeps the plant life of the sea is extinguished for want of light. At a hundred metres beneath the surface only a few Algæ are found. These are plants of the shade, needing little light. Some of them continue to grow without interruption through the three months' polar night of Spitzbergen, and develop their invisible flowers and fruits at this season with the temperature of the water below the freezing point. The giants of the Algæ seek the enjoyment of uninterrupted sunlight. They grow in the deep waters near the shore, and send up slender stalks which pass at the surface of the water into long, shredded leaf forms. Algæ of this kind form, on the Chilian coast, for instance, forests in which specimens may be found more than two hundred metres long.