But in this chapter we are concerned with the Vegetable Life of the ocean, and we must therefore let the wonderful Radiolarians alone.
Properly the chapter on Vegetables ought to have come before any chapter on Animals, since we have been climbing upward from inanimate Nature, and since all vegetables rank below all animals. When on the topic of Ocean-building, however, the subject of Chalk seemed to follow naturally after that of Sandstone. And this little volume makes no pretensions to stiff classification.
No surprise need be felt at vegetables being able to make or “secrete” flint and chalk. This making is, as we have seen, an unconscious work. The living jelly-speck secretes automatically, not with intention.
Such secreting is not confined to ocean vegetables. Trees and plants on land manufacture a host of substances—sweet oil, cocoa-nut milk, indiarubber, and countless others.[2] Forest trees in like manner grow their own framework of hard wood, which may be said to take the place with them of a skeleton.
[2] The spicules of silica may be seen on coarse grass, secreted by the grass.
All this is a part of Life. Inanimate rocks and stones may lie for centuries unchanged, except through friction with other rocks and stones, or with running water. But where Life reigns, though it be of the simplest kind, there growth and development must follow.
Life, from its very nature, cannot mean stagnation, or standing still. It must always be assimilating. It must always be expanding. It must always be doing. When these things cease, death has begun.
So much alike are the lower forms of life in the two classes, that many an animal has been for a time mistakenly called a vegetable, and many a vegetable has been for a while supposed to be an animal. The foraminifera were once ranked as vegetables, and the diatoms were ranked as animals.
In deep-sea regions, dark and cold, no vegetable life can possibly exist, not even the almost ubiquitous diatoms. But their remains are present in vast multitudes. As the tiny plant-life dies out, the little hard vegetable-cases sink to the ocean-bed, there to mingle with gathering muds and oozes—there, too, in the course of ages, to be transformed into Flint.
Diatoms flourish on land as well as in the ocean; in cold climates as well as in warm. On the whole they prefer the colder regions, therein differing from the warmth-loving foraminifera. Sometimes immense floating banks of these microscopic plants are found, reaching through many miles. A net, lowered into such a bank and then drawn up, is filled with a “brown-coloured slimy and felt-like mass,” made up chiefly of uncountable myriads of diatoms.