The thickly peopled countries of the Temperate Zone must look more and more to the tropics to supplement their own food resources, whether by direct supplies, made possible in increasing measure by ever-improving means of transportation, or by furnishing plants which may be cultivated in mild-wintered regions such as California and Florida. Both forms of contribution will be largely in the item of fruits. As examples of the first class, the banana, because of its immense yield and quick production, has already been exploited on a large scale, and the coconut, through its product copra, has become an economic factor of prime importance; in the second (or rather, in both) the avocado, still a novelty but of very great possibilities as adaptable to growth in our own country, is on the verge of taking a high place among the food crops contributed by the tropics.
Many other fruits of the Torrid Zone, not all of them so important, yet all valuable in degree in the dietary of the race, must be grown in ever-increasing quantities, not only to supply northern markets, but also, - and even more important, -to enable the native populations of the tropics as well as settlers from the North to obtain abundantly and cheaply this most wholesome source of human energy.
For, strange as it may seem to many who have never lived or traveled in the hot belts of the earth, those lands come far short of conforming to that conventional idea of the tropics, as regions where luscious fruits grow wild upon every tree and the languorous native has only to stretch forth his hand to obtain his dinner. It is a well-attested fact that the inhabitants of many tropical countries suffer for want of sufficient fresh fruit; and it is also true that much real starvation in densely populated hot regions, India for example, could be averted by planting on a wholesale scale fruit-trees such as the avocado, whose product has a relatively high food value.
The reason for this scarcity of fruits in precisely those regions where, by climatic indications, one would expect them to be most abundant, is not to be found in any single fact, but is, perhaps, largely the result of three causes: first, the enervating effect of heat, which discourages man from undertaking work which can be avoided; second, the one-sided exploitation of many tropical regions for the production of materials such as rubber and cotton, without sufficient regard to supplying wholesome foodstuffs for those who labor in producing these articles; and third, the long time required by tree-fruits to yield returns, as compared with the annual crops such as corn, beans, and squashes. This last factor is particularly disastrous where primitive races of people are concerned, for such almost invariably devote their attention in the main to crops which give quick returns, - the very crops which must depend absolutely on the season's rainfall.
It is, indeed, only as scattered, often neglected, specimens in dooryards and around cultivated fields that many of the tropical fruit-trees exist. Others, such as the mango and the breadfruit, are given more attention, yet they rarely receive more than a fraction of the solicitous care which northerners lavish on their apples, peaches, and pears.
With the exception of a few species, such as the banana and the coconut, the tropical fruits have received scientific attention only when their culture has been brought northward to the extreme limit of their zone, as, in the case of certain of them, it has been in California and Florida. Even here their study and improvement have only been undertaken in very recent years; many species, in fact, are still in the condition of wild plants, so that it is no wonder their fruits are sometimes looked on by northern horticulturists as almost without value. The case is well put by Hartwig, who writes, in his work "The Tropical World":
"It may easily be imagined that the tropical sun, which distills so many costly juices and fiery spices in indescribable multiplicity and abundance, must also produce a variety of fruits. But man has yet done little to improve by care and art these gifts of Nature, and, with rare exceptions, the delicious flavor for which our native fruits are indebted to centuries of cultivation, is found wanting in those of the torrid zone. In our gardens Pomona appears in the refined garb of civilization, while in the tropics she still shows herself as a savage beauty, requiring the aid of culture for the full development of her attractions."
The exceptions to this condition, however, are notable, and scarcely so rare as Hartwig and others have believed. The mango, in its finer Indian varieties, offers an example of improvement through selection and vegetative propagation which equals that of the peach, if indeed the advance from wild to cultivated forms has not been greater in the former than in the latter fruit. Those who have tasted the luscious Pairi mango of Bombay, or the Mulgoba as now grown in Florida, will recognize the probable accuracy of this statement.
Many other tropical fruits might be mentioned which compare favorably with the best products of high cultivation in the Temperate Zone. Who, that has had the opportunity of judging, has not felt, as he lifted the snowy segments of the mangosteen from their cup of royal purple, that here was a fruit not excelled by any other in the world? The cherimoya of tropical America leaves little to be desired, while the litchi is preferred in China, not without reason, to the finest orange or peach. American residents in Hawaii consider the papaya the most delicious of breakfast-fruits, surpassing in their estimation the cantaloupe or muskmelon. To the Japanese taste there is no better fruit than the kaki, while to the Arab the date is the quintessence of richness and flavor.
The ignorance, or tardiness of adoption, of the art of grafting has, in many tropical countries, prevented the development of superior fruits. The superb apples and pears of the Temperate Zone, and the splendid mangos of India, could not be grown without grafting, since improved varieties of nearly all tree-fruits tend to revert to the wild type when propagated by seed. The finest fruits are, in fact, artificial productions which can only be maintained by artificial means; under free competition of natural selection they would disappear.