Missionary Travels and Researches in South Africa. David LivingstoneЧитать онлайн книгу.
than the Kalahari. When first taken possession of, these parts are said to have been covered with a coating of grass, but that has disappeared with the antelopes which fed upon it, and a crop of mesembryanthemums and crassulas occupies its place. It is curious to observe how, in nature, organizations the most dissimilar are mutually dependent on each other for their perpetuation. Here the original grasses were dependent for dissemination on the grass-feeding animals, which scattered the seeds. When, by the death of the antelopes, no fresh sowing was made, the African droughts proved too much for this form of vegetation. But even this contingency was foreseen by the Omniscient One; for, as we may now observe in the Kalahari Desert, another family of plants, the mesembryanthemums, stood ready to neutralize the aridity which must otherwise have followed. This family of plants possesses seed-vessels which remain firmly shut on their contents while the soil is hot and dry, and thus preserve the vegetative power intact during the highest heat of the torrid sun; but when rain falls, the seed-vessel opens and sheds its contents just when there is the greatest probability of their vegetating. In other plants heat and drought cause the seed-vessels to burst and shed their charge.
One of this family is edible ('Mesembryanthemum edule'); another possesses a tuberous root, which may be eaten raw; and all are furnished with thick, fleshy leaves, having pores capable of imbibing and retaining moisture from a very dry atmosphere and soil, so that, if a leaf is broken during a period of the greatest drought, it shows abundant circulating sap. The plants of this family are found much farther north, but the great abundance of the grasses prevents them from making any show. There, however, they stand ready to fill up any gap which may occur in the present prevailing vegetation; and should the grasses disappear, animal life would not necessarily be destroyed, because a reserve supply, equivalent to a fresh act of creative power, has been provided.
One of this family, 'M. turbiniforme', is so colored as to blend in well with the hue of the soil and stones around it; and a 'gryllus' of the same color feeds on it. In the case of the insect, the peculiar color is given as compensation for the deficiency of the powers of motion to enable it to elude the notice of birds. The continuation of the species is here the end in view. In the case of the plant the same device is adopted for a sort of double end, viz., perpetuation of the plant by hiding it from animals, with the view that ultimately its extensive appearance will sustain that race.
As this new vegetation is better adapted for sheep and goats in a dry country than grass, the Boers supplant the latter by imitating the process by which graminivorous antelopes have so abundantly disseminated the seed of grasses. A few wagon-loads of mesembryanthemum plants, in seed, are brought to a farm covered with a scanty crop of coarse grass, and placed on a spot to which the sheep have access in the evenings. As they eat a little every night, the seeds are dropped over the grazing grounds in this simple way, with a regularity which could not be matched except at the cost of an immense amount of labor. The place becomes in the course of a few years a sheep-farm, as these animals thrive on such herbage. As already mentioned, some plants of this family are furnished with an additional contrivance for withstanding droughts, viz., oblong tubers, which, buried deep enough beneath the soil for complete protection from the scorching sun, serve as reservoirs of sap and nutriment during those rainless periods which recur perpetually in even the most favored spots of Africa. I have adverted to this peculiarity as often seen in the vegetation of the Desert; and, though rather out of place, it may be well—while noticing a clever imitation of one process in nature by the Cape farmers—to suggest another for their consideration. The country beyond south lat. 18 Deg. abounds in three varieties of grape-bearing vines, and one of these is furnished with oblong tubers every three or four inches along the horizontal root. They resemble closely those of the asparagus. This increase of power to withstand the effects of climate might prove of value in the more arid parts of the Cape colony, grapes being well known to be an excellent restorative in the debility produced by heat: by ingrafting, or by some of those curious manipulations which we read of in books on gardening, a variety might be secured better adapted to the country than the foreign vines at present cultivated. The Americans find that some of their native vines yield wines superior to those made from the very best imported vines from France and Portugal. What a boon a vine of the sort contemplated would have been to a Rhenish missionary I met at a part in the west of the colony called Ebenezer, whose children had never seen flowers, though old enough to talk about them!
The slow pace at which we wound our way through the colony made almost any subject interesting. The attention is attracted to the names of different places, because they indicate the former existence of buffaloes, elands, and elephants, which are now to be found only hundreds of miles beyond. A few blesbucks ('Antilope pygarga'), gnus, bluebucks ('A. cerulea'), steinbucks, and the ostrich ('Struthio camelus'), continue, like the Bushmen, to maintain a precarious existence when all the rest are gone. The elephant, the most sagacious, flees the sound of fire-arms first; the gnu and ostrich, the most wary and the most stupid, last. The first emigrants found the Hottentots in possession of prodigious herds of fine cattle, but no horses, asses, or camels. The original cattle, which may still be seen in some parts of the frontier, must have been brought south from the north-northeast, for from this point the natives universally ascribe their original migration. They brought cattle, sheep, goats, and dogs; why not the horse, the delight of savage hordes? Horses thrive well in the Cape Colony when imported. Naturalists point out certain mountain ranges as limiting the habitat of certain classes of animals; but there is no Cordillera in Africa to answer that purpose, there being no visible barrier between the northeastern Arabs and the Hottentot tribes to prevent the different hordes, as they felt their way southward, from indulging their taste for the possession of this noble animal.
I am here led to notice an invisible barrier, more insurmountable than mountain ranges, but which is not opposed to the southern progress of cattle, goats, and sheep. The tsetse would prove a barrier only until its well-defined habitat was known, but the disease passing under the term of horse-sickness (peripneumonia) exists in such virulence over nearly seven degrees of latitude that no precaution would be sufficient to save these animals. The horse is so liable to this disease, that only by great care in stabling can he be kept any where between 20 Deg. and 27 Deg. S. during the time between December and April. The winter, beginning in the latter month, is the only period in which Englishmen can hunt on horseback, and they are in danger of losing all their studs some months before December. To this disease the horse is especially exposed, and it is almost always fatal. One attack, however, seems to secure immunity from a second. Cattle, too, are subject to it, but only at intervals of a few, sometimes many years; but it never makes a clean sweep of the whole cattle of a village, as it would do of a troop of fifty horses. This barrier, then, seems to explain the absence of the horse among the Hottentots, though it is not opposed to the southern migration of cattle, sheep, and goats.
When the flesh of animals that have died of this disease is eaten, it causes a malignant carbuncle, which, when it appears over any important organ, proves rapidly fatal. It is more especially dangerous over the pit of the stomach. The effects of the poison have been experienced by missionaries who had eaten properly cooked food, the flesh of sheep really but not visibly affected by the disease. The virus in the flesh of the animal is destroyed neither by boiling nor roasting. This fact, of which we have had innumerable examples, shows the superiority of experiments on a large scale to those of acute and able physiologists and chemists in the laboratory, for a well known physician of Paris, after careful investigation, considered that the virus in such cases was completely neutralized by boiling.
This disease attacks wild animals too. During our residence at Chonuan great numbers of tolos, or koodoos, were attracted to the gardens of the Bakwains, abandoned at the usual period of harvest because there was no prospect of the corn ('Holcus sorghum') bearing that year. The koodoo is remarkably fond of the green stalks of this kind of millet. Free feeding produced that state of fatness favorable for the development of this disease, and no fewer than twenty-five died on the hill opposite our house. Great numbers of gnus and zebras perished from the same cause, but the mortality produced no sensible diminution in the numbers of the game, any more than the deaths of many of the Bakwains who persisted, in spite of every remonstrance, in eating the dead meat, caused any sensible decrease in the strength of the tribe.
The farms of the Boers consist generally of a small patch of cultivated land in the midst of some miles of pasturage. They are thus less