While there is thus very little or in fact almost no struggle for water in the rain forest, the struggle for light is intense. In the deepest and most luxuriant of them the gloom of the forest floor is notorious and it was by no means a figure of speech for Stanley to describe his trip through equatorial Africa as “Through the Dark Continent.” So dark are most rain forests, and, as we have seen in a previous chapter, so inexorable are the plants’ demands for light, that the various devices to insure it are perhaps the one great difference between these forests and those of temperate regions. One effect of the struggle for light is the enormous production of vines often running hundreds of feet through the tree tops. In India the Calamus, or rattan palms, with stems no thicker than a walking-stick, will completely interlace the foliage of the canopy. Thousands of slender whiplike roots and stems of such plants descend from the topmost heights of the forest canopy, where the plants to which they are attached make such an inextricable tangle among the tree tops that orchid collectors have been known to travel considerable distances over the matted vegetation, with, it must be confessed, considerable danger. These vines or lianes as they are called, are however, often as thick as a man’s body and armed with great hooked prickles, an obvious aid in catching some support to reach that essential light for which all plants in such places are ever striving.
Besides the bewildering tangle caused by these lianes, the rain forest is further impeded by hosts of epiphytes or plants that are mechanically attached to tree trunks, branches, or anything else that will raise them to the light. Of all the plants of such regions the epiphytes are the most light-demanding. They must not be mistaken for parasites, as they have roots of their own through which they absorb nourishment, mostly as water vapor, but also as liquid water held in the bark and refuse in which they grow. Thousands of orchids are epiphytes, also ferns, and, only in the American tropics, thousands of different relatives of the pineapple. Many of the latter are among the most gorgeously colored of all plants, their superb foliage being much sought after and the specimens largely grown in our greenhouses. In most rain forests every available inch of space is covered by these epiphytes, so that no bark, scarcely any branches, are to be seen but those clothed in this motley array of plants that use the support to get the utmost possible light. Many of these epiphytes have rosettes of leaves arranged for holding water, and after a sharp thunder shower followed by fresh wind the writer has seen the ground strewn with thousands of relatives of the pineapple which, with the added supply of water, were unable to stand the strain and were consequently wrenched from their lofty perch. So enormous is the combined weight of these epiphytes, together with the lianes, that many trees crash down under the strain long before their time. Perhaps no sight of the rain forest so convinces one of the struggle for light as to see one of these forest monarchs come crashing down loaded with thousands of plants that have been using it for support, and to escape which it has pushed its canopy to the utmost limits of its growth. Such contests are common in a forest of which only the barest outlines can be conveyed to those who have never seen it. To those who have had that good fortune any description palls beside the wonderful actuality.
It is scarcely to be wondered at that these steaming rain forests with their gloom, and, as they were once described, “all hung about with fever trees,” should be dreaded by many, and the subject of fabulous tales to the credulous. The almost incredible difficulty of getting through them, not to mention the savage animals that inhabit many of them, have not lessened the tendency to exaggerate about these great forests. But the truth about them is so far beyond belief, the strange plants that intrepid explorers have brought out of them so almost incredible, that it only excited a temporary wonderment when the largest flower in the world was discovered in such a forest in the Malayan Archipelago.
Sir Stanford Raffles and Dr. Arnold, while exploring in Sumatra during the year 1818, discovered what was called “the greatest prodigy of the vegetable world,” and no flower since found equals its size. The plant, without stem or leaves, consists wholly of one gigantic flower about nine feet in circumference, and was subsequently called Rafflesia Arnoldii. It aroused a sensation in England which was not abated by knowledge of the fact that the flower is a parasite on the stems of certain tropical plants related to the grape. That such a huge flower should be the product of a parasitic mode of life is one more illustration of how this and related irregularities occur in widely separated families of plants, and under varying conditions. Relatives of it have since been found in India, some parasitic on roots, others, as in Rafflesia Arnoldii, on the stems of vines. The sticky seeds are in all probability carried from place to place on the hoofs of elephants, to which they have been known to cling. Only if they are deposited on a bruised or otherwise exposed tissue of their future host can they grow. These curious plants have been actually cultivated in the greatest tropical botanical garden in the world, at Buitenzorg, Java.
The original collectors of Rafflesia Arnoldii could scarcely credit their senses when they saw for the first time this extraordinary plant, whose whole life is spent in producing this great flower and fruit. As one of them says: “Had I been alone, and had there been no witnesses, I think I should have been fearful of mentioning the dimensions of this flower, so much does it exceed every flower I have ever seen or heard of.” The odor of the flower is repulsive, and, with its great size and curious mode of growth in the dark rain forest, it is surely one of the strangest productions of the vegetable world.
But as the utmost development of the plant world, and producing the greatest profusion and richness of plant life, these rain forests are, beyond the sporadic occurrence of such wonders as Rafflesia and some others, places of extraordinary interest. With every inch of space occupied by plants, the very epiphytes often having on their leaves still smaller plants, we see here what nature will produce when the maximum conditions for plant growth are so nearly perfect. Theodore Roosevelt in his book, “Through the Brazilian Wilderness,” gives a vivid picture of the rain forest there, and it may well end our account of those most interesting of all plant societies:
“In one grove the fig trees were killing the palms, just as in Africa they kill the sandalwood trees. In the gloom of this grove there were no flowers, no bushes; the air was heavy; the ground was brown with moldering leaves. Almost every palm was serving as a prop for a fig tree. The fig trees were in every stage of growth. The youngest ones merely ran up the palms as vines. In the next state the vine had thickened and was sending out shoots, wrapping the palm stem in a deadly hold.
“Some of the shoots were thrown round the stem like the tentacles of an immense cuttlefish. Others looked like claws that were hooked into every crevice, and round every projection. In the stage beyond this the palm had been killed, and its dead carcass appeared between the big, winding vine trunks; and later the palm had disappeared and the vines had united in a great fig tree. Water stood in black pools at the foot of the murdered trees, and of the trees that had murdered them. There was something sinister and evil in the dark stillness of the grove; it seemed as if sentient beings had writhed themselves round and were strangling other sentient beings.”
Many other forests in the tropics, where the rainfall is less, or less regularly distributed, are not unlike our own, having rather regular periods of leaf-fall that come with the dry season rather than with the autumn. The trees are of course never the same as ours, but the general aspect is not very different from that of temperate forests.