Yet there were many, not always botanists, of much older date, who made great discoveries in the science. Leonardo da Vinci, the great painter, seems to have had quite a definite idea of the growth of trees, for he found out that the annual rings on a tree-stem are thin on the northern and thick on the southern side of the trunk. Dante[10] seems to have also understood the effect of sunlight in ripening the vine and producing the growth of plants (Purgatorio, xxv. 77). Goethe seems to have been almost the first to understand how leaves can be changed in appearance when they are intended to act in a different way. Petals, stamens, as well as some tendrils and spines, are all modified leaves. There is also a passage in Virgil, or perhaps more distinctly in Cato, which is held to show that the ancients knew that the group of plants, Leguminosæ, in some way improved the soil. I have also tried to show that Shelley had a more or less distinct idea of the "warning" or conspicuous colours (reds, purples, spotted, and speckled) which are characteristic of many poisonous plants (see p. [238]).
But if we begin with the unlettered savage, one can trace the very slow and gradual growth of the science of plant-life persisting all through the Dark Ages, the Middle Ages, and recent times, until about fifty or sixty years ago, when a sudden great development began, which gives us, we hope, the promise of still more wonderful discoveries.
CHAPTER III
A TREE'S PERILOUS LIFE
Hemlock spruce and pine forests—Story of a pine seedling—Its struggles and dangers—The gardener's boot—Turpentine of pines—The giant sawfly—Bark beetles—Their effect on music—Storm and strength of trees—Tall trees and long seaweeds—Eucalyptus, big trees—Age of trees—Venerable sequoias, oaks, chestnuts, and olives—Baobab and Dragontree—Rabbits as woodcutters—Fire as protection—Sacred fires—Dug-out and birch-bark canoes—Lake dwellings—Grazing animals and forest destruction—First kind of cultivation—Old forests in England and Scotland—Game preserving.
"The murmuring pines and the hemlocks
Stand like harpers hoar with beards that rest on their bosom."—Longfellow.
OF course the Hemlock here alluded to is not the "hemlock rank growing on the weedy bank," which the cow is adjured not to eat in Wordsworth's well-known lines. (If the animal had, however, obeyed the poet's wishes and eaten "mellow cowslips," it would probably have been seriously ill.) The "Hemlock" is the Hemlock spruce, a fine handsome tree which is common in the forests of Eastern North America.
These primeval forests of Pine and Fir and Spruce have always taken the fancy of poets. They are found covering craggy and almost inaccessible mountain valleys; even a tourist travelling by train cannot but be impressed by their sombre, gloomy monotony, by their obstinacy in growing on rocky precipices on the worst possible soil, in spite of storm and snow.