One of the most interesting facts in plantdom is the alliance maintained by Clovers, Beans, Vetches and other leguminous plants, with Bacteria belonging to the class Pseudomonas. No soil can be fertile unless it contains organic compounds of nitrogen. The earth Bacteria have discovered methods of producing these important substances, possibly extracting nitrogen distributed through the ground. These minute parasites attach themselves to the roots of the larger plants, which promptly enclose them in cysts or nodules where they can lead a sheltered life and manufacture assimilable food compounds for their hosts. When they die, the owners of the roots feed upon their bodies.
What is the art of grafting but a form of artificial parasitism? Very often a branch or cutting is made to form a bodily union with some plant of an entirely dissimilar species. In some cases, the intruder sends roots into the tissue of its host like a true dependent. Grafts of Prickly Pears, Mexican Grapevines and Agaves put forth food-suckers in the soft flesh of the Giant Cactus or the Barrel Cactus much as they would do if planted in the earth. There is here no true diffusive union of partners but mere absorption on the part of the invader.
Even grafting of allied species of Grapes sometimes results in the young plants sending roots through the tissues of the scion, eventually reaching the earth by way of the body of the host. In such cases, the parasite also draws nutriment from its messmate by means of a superior osmotic pressure.
Almost everything lies in the point of view. No man, no animal, no plant is so debased and degraded that it does not radiate some little measure of helpfulness. If “all things work together for good,” even that member of a plant union which seems to act upon that inverted principle of “all coming in and nothing going out” has its legitimate place in the world. As for those numerous examples of share-alike partnerships, they illustrate the principle of the divine law of love which lies back of and above the very real hardships and cruelties of this work-a-day world.
FRIENDLY ALLIES BY THE WATER’S EDGE
CHAPTER V
Allies of the Plant World
“I wish I were a willow tree—
Young wind in the green hair of me
And old brown water round my feet,
And a familiar bird to greet.”
—Elizabeth Fahnestock.
Every division of terrestrial life constitutes a struggle. The plants grow and carry on their business and social activities so unobtrusively that we seldom think of them as appealing to arms—yet their whole existence is a battle royal. They must fight with aspiring neighbours for every inch of their upward growth, and at the same time wage incessant warfare against a hundred insects and animal foes.