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It is true that, as they are all low-growing herbs or shrubs with delicate foliage, they might possibly be liable to destruction by herbivorous animals, and might escape by their singular power of suddenly collapsing before the jaws opened to devour them. The fact that one species has been naturalized as a weed over so wide an area in the tropics, seems to show that it possesses some advantage over the generality of tropical weeds. It is however curious that, as most of the species are somewhat prickly, so easy and common a mode of protection as the development of stronger spines should here have failed; and that its place should be supplied by so singular a power as that of simulating death, in a manner which suggests the possession of both sensation and voluntary motion. Comparative Scarcity of Flowers.--It is a very general opinion among inhabitants of our temperate climes, that amid the luxuriant vegetation of the tropics there must be a grand display of floral beauty; and this idea is supported by the number of large and showy flowers cultivated in our hot-houses. The fact is, however, that in proportion as the general vegetation becomes more luxuriant, flowers form a less and less prominent feature ; and this rule applies not only to the tropics but to the temperate and frigid zones. It is amid the scanty vegetation of the higher mountains and towards the limits of perpetual snow, that the alpine flowers are most brilliant and conspicuous. Our own meadows and pastures and hill-sides produce more gay flowers than our woods and forests; and, in the tropics, it is in the parts where vegetation is less dense and luxuriant that flowers most abound. In the damp and uniform climate of the equatorial zone the mass of vegetation is greater and more varied than in any other part of the globe, but in the great virgin forests themselves flowers are rarely seen. After describing the forests of the Lower Amazon, Mr. Bates asks: “But where were the flowers ? To our great disappointment we saw none, or only such as were insignificant in appearance. Orchids are rare in the dense forests of the lowlands, and I believe it is now tolerably well ascertained that the majority of the forest-trees in equatorial Brazil have small and inconspicuous flowers.” My friend Dr. Richard Spruce assured me that by far the greater part of the plants gathered by him in equatorial America had inconspicuous green or white flowers. My own observations in the Aru Islands for six months, and in Borneo for more than a year, while living almost wholly in the forests, are quite in accordance with this view. Conspicuous masses of showy flowers are so rare, that weeks and months may be passed without observing a single flowering plant worthy of special admiration. Occasionally some tree or shrub will be seen covered with magnificent yellow, or crimson, or purple flowers, but it is usually an oasis of colour in a desert of verdure, and therefore hardly affects the general aspect of the vegetation. The equatorial forest is too gloomy for flowers, or generally even for much foliage, except of ferns and other shade-loving plants; and were it not that the forests are broken up by rivers and streams, by mountain ranges, by precipitous rocks and by deep ravines, there would be far fewer flowers than there are. Some of the great forest-trees have showy blossoms, and when these are seen from an elevated point looking over an expanse of tree-tops the effect is very grand ; but nothing is more erroneous than the statement sometimes made that tropical forest-trees generally have showy flowers, for it is doubtful whether the proportion is at all greater in tropical than in temperate zones. On such natural exposures as steep mountain sides, the banks of rivers, or ledges of precipices, and on the margins of such artificial openings as roads and forest clearings, whatever floral beauty is to be found in the more luxuriant parts of the tropics is exhibited. But even in such favourable situations it is not the abundance and beauty of the flowers but the luxuriance and the freshness of the foliage, and the grace and infinite variety of the forms of vegetation, that will most attract the attention and extort the admiration of the traveller. Occasionally indeed you will come upon shrubs gay with blossoms or trees festooned with flowering creepers; but, on the other hand, you may travel for a hundred miles and see nothing but the varied greens of the forest foliage and the deep gloom of its tangled recesses. In Mr. Belt's Naturalist in NicaTagua, he thus describes the great virgin forests of that country which, being in a mountainous region and on the margin of the equatorial zone, are among the most favourable examples. “On each side of the road great trees towered up, carrying their crowns out of sight amongst a canopy of foliage, and with lianas hanging from nearly every bough, and passing from tree to tree, entangling the giants in a great network of coiling cables. Sometimes a tree appears covered with beautiful flowers which do not belong to it, but to one of the lianas

| The Naturalist on the River Amazons, 2nd edit. p. 38.

that twines through its branches and sends down great rope-like stems to the ground. Climbing ferns and vanilla cling to the trunks, and a thousand epiphytes perch themselves on the branches. Amongst these are large arums that send down long aerial roots, tough and strong, and universally used instead of cordage by the natives. Amongst the undergrowth several small species of palms, varying in height from two to fifteen feet, are common ; and now and then magnificent tree ferns sending off their feathery crowns twenty feet from the ground delight the sight by their graceful elegance. Great broad-leaved heliconias, leathery melastomae, and succulent-stemmed, lop-sided leaved and flesh-coloured begonias are abundant, and typical of tropical American forests; but not less so are the cecropia trees, with their white stems and large palmated leaves standing up like great candelabra. Sometimes the ground is carpeted with large flowers, yellow, pink, or white, that have fallen from some invisible tree-top above ; or the air is filled with a delicious perfume, the source of which one seeks around in vain, for the flowers that cause it are far overhead out of sight, lost in the great overshadowing crown of verdure.” Although, as has been shown elsewhere, it may be doubted whether light directly produces floral colour, there can be no doubt that it is essential to the growth of vegetation and to the full development of foliage and of flowers. In the forests all trees, and shrubs, and creepers struggle upwards to the light, there to expand their blossoms and ripen their fruit. Hence, perhaps, the abundance of climbers which make use of their more sturdy companions to reach this necessary of vegetable life. Yet even on the upper, surface of the forest, fully exposed to the light and heat of the tropical sun, there is no special development of coloured flowers. When from some elevated point you can gaze down upon an unbroken expanse of woody vegetation, it often happens that not a single patch of bright colour can be discerned. At other times, and especially at the beginning of the dry season, you may behold scattered at wide intervals over the mottled-green surface a few masses of yellow, white, pink, or more rarely of blue colour, indicating the position of handsome flowering treeS. The well-established relation between coloured flowers and the need of insects to fertilize them, may perhaps be connected with the comparative scarcity of the former in the equatorial forests. The various forms of life are linked together in such mutual dependence that no one can inordinately increase without bringing about a corresponding increase or diminution of other forms. The insects which are best adapted to fertilize flowers cannot probably increase much beyond definite limits, because in doing so they would lead to a corresponding increase of insectivorous birds and other animals which would keep them down. The chief fertilizers—bees and butterflies—have enemies at every stage of their growth, from the egg to the perfect insect, and their numbers are, therefore, limited by causes quite independent of the supply of vegetable food. It may, therefore, be the case that the numbers of suitable insects are totally inadequate to the fertilization of the countless millions of forest-trees over such vast areas as the equatorial zone presents, and that, in consequence, a large proportion of

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