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Romance of Plant Life

<h2>CHAPTER X ON DESERTS</h2> What are deserts like?—Camel-riding—Afterglow—Darwin in South America—Big Bad Lands—Plants which train themselves to endure thirst—Cactus and euphorbia—Curious shapes—Grey hairs—Iceplant—Esparto grass—Retama—Colocynth—Sudden flowering of the Karoo—Short-lived flowers—Colorado Desert—Date palms on the Nile—Irrigation in Egypt—The creaking Sakkieh—Alexandria hills—The Nile and Euphrates. ACROSS the whole of Africa, at its very broadest part, from the dominions of the Emperor of the Sahara at Cape Juby on the Atlantic, and to the very borders of British India, stretches a desert of the most uncompromising character. It is famous in history: the strongest races of man, the great religions of the world, as well as most cultivated plants and domestic animals, have originated in some part of this dreary waste. One cannot really appreciate deserts unless one has really seen them. But it is necessary to try to describe what they are like. Sometimes the desert is a wilderness of broken, stony hills covered by angular pieces of shivered rock. In other places the soil is hard, and is everywhere covered by pebbles or shingle. Often it is a mere waste of sand blown into downs and hillocks which look sometimes like the sand dunes by the coast, and elsewhere like the waves of the sea. 132 One finds valleys in the desert quite like ordinary ones in shape, but instead of water there is only sand in sweeping curves and hollows, like the snow-wreaths and drifts in a highland glen. Rocks stand out of this, but their projecting faces are polished smooth and glittering or deeply cut by the flinty particles scraping over them continually in storms and hurricanes. The traveller on camel-back, where his waist has to act as a sort of universal joint giving to every unexpected jolt and wrench of his rough-paced mount, suffers from the heat, for nowhere else in the world are there such high temperatures. He suffers from thirst, and still more from the dust which fills eyes, mouth, nostrils, and ears. Yet the dry pure air is most exhilarating. In the evening there is a feast for the eyes in the glorious afterglow when the sun has just set. The light from below the horizon produces an ever-changing, indescribable play of colour from violet to salmon pink and through the most delicate shades of yellow, blue, and rose, until everything fades and there reigns only the mysterious silence of the beautiful starlit night. No wonder the air is dry and pure, for rain only falls on perhaps eight days in the year in some places (Ghardiaia). Yet plants manage to exist even where there is only about seven inches of rain annually. But this seems still more extraordinary if one remembers that sand may be almost glowing hot during the day, whilst in winter it may be, at night, cooled below the freezing-point. Yet a desert absolutely bare of plants is an exceedingly rare phenomenon. Such do occur. Darwin speaks of "an undulating country, a complete and utter desert." This is not 133 very far from Iquique in South America. "The road was strewed with the bones and dried skins of the many beasts of burden which had perished upon it from fatigue. Excepting the Vultur aura, which preys on the carcases, I saw neither bird, quadruped, reptile, nor insect. On the coast mountains, at the height of about 2000 feet, where, during this season, the clouds generally hang, a very few cacti were growing in the clefts of rock; and the loose sand was strewed over with a lichen which lies on the surface quite unattached. ... In some parts it was in sufficient quantity to tinge the sand, as seen from a distance, of a pale yellowish colour. Farther inland, during the whole ride of fourteen leagues, I saw only one other vegetable production, and that was a most minute yellow lichen, growing on the bones of the dead mules."[61] Rydberg, speaking of the Big Bad Lands in South Dakota, says that there are in some places great stretches of land consisting of cañons separated by small ridges, in which not a speck of green is visible over several sections.[62] (A section is more than a square mile.) But though Aden looks exactly like "a barrack stove that no one's lit for years and years," plants grow there. Even in Egypt, when one has left the Nile inundation limit, a botanical eye very seldom fails to detect plants of one sort or another even in a dangerous and thorough-going desert. Plants are almost as hardy as men; they can adapt themselves to almost any climate. In some curious and inexplicable way the very dangers of the climate seem to produce automatically a means of resisting it. The chief peril, of course, is a loss of the precious 134 water through the leaves. When the skin or epidermis of a plant is being formed, the walls of its cells are laid down, layer by layer, one inside the other, by the secretion of the living matter inside. In a dry desert the loss of water by evaporation will be so rapid that these layers of cell-wall are much thicker than in ordinary plants. The very fact that they are thicker and less penetrable tends to prevent any further loss of water.[63] So that plants in a dry climate have the power of altering themselves to resist its dangers. Another author found that, in Scandinavia, plants of the same species can acclimatize themselves if necessary. Sheep's Sorrel which had grown on dry, droughty gravel banks only lost 10 per cent. of its water in the first two days, when it was artificially dried. Other Sheep's Sorrels, which had been luxuriating in meadows where they had no lack of moisture, lost no less than one third (33 per cent.) of their water when dried in the same way. That is interesting, because very likely our readers might in crossing a desert be perishing of thirst when a Bedouin Arab would be perfectly happy. The plants have learnt to do without water just in the same way as the Arab has done. Of the many interesting desert plants, the Succulents, Cacti, Euphorbias, and others of the same extraordinary, fleshy, dropsical appearance, come first. When a Cereus plant (one of the American Giant Cacti) was dried, it did not lose the whole of its water for 576 days. That is probably the longest time "between drinks" on record. A Houseleek (Sempervivum), which has to grow on dry rocks where it has no water for days together, remained quite fresh for 165 days. <div></div> <div class="figcenter"> <ANTIMG class="mw" src="images/i_134.jpg" alt="" /> <div class="caption"> Giant Cactus near Aconcagua Valley, Chile This plant was about 8 feet high. The darker part on the tallest branch is the dark red flower of the parasitic horanthus. The thorns covering the branches are quite distinct. </div> </div> 135 There are several reasons why these plants took so long to dry up. To begin with, they have inside their stems and leaves certain substances which hold water and delay its escape. Moreover their extraordinary shapes are of very great assistance. They prefer globular, round, circular, pear-shaped, or cylindrical forms. Suppose you were to cut such a round mass into thin slices and lay them out flat, it is quite clear that they would cover a much greater surface. Thin leaves also, if squashed up into a round ball, would have a very much smaller surface. The water can only escape from the surface exposed, so that these condensed round balls and fleshy columns have far less water-losing surface than ordinary leaves. As a matter of fact, it was found by calculation that the surface of an Echinocactus was 300 times less for the same amount of stuff as that of an Aristolochia leaf. If the actual loss of water from the Echinocactus, as found by experiment, was reckoned as one unit per square inch, then the amount of water lost from a square inch of the Aristolochia was no less than 5000 units! This shows that these odd, outrageous shapes of Prickly Pears, Cacti, and other succulents are an extraordinary help to them. We have already pointed out in a previous chapter how necessary their spines and prickles are if they must resist rats, mice, camels, and other enemies. What we may call the "hedgehog" type of plant is also very common in desert countries. There are many woody little, much branched, twiggy shrublets, which bristle all over with thorns and spines. They are not at all fleshy, but do with the least conceivable amount of water. Another striking characteristic of the desert flora is noticed by every one. Almost every plant is clothed either 136 in white cottonwool, like the Lammie's Lug of our gardens, or else in grey hairs. The general tint of the landscape is not green, but it is rather the colour of the soil silvered over by these grey-haired plants. The reason of this is, of course, quite easy to understand. We put on a thick overcoat if we are going to walk in a Scotch mist, to keep out the moisture. These plants cover themselves with hairs or cottonwool to keep the moisture inside. It does not escape easily through the woolly hairs on the skin. One very strange plant should be noticed here. This is the Iceplant (Mesembryanthemum cristallinum). Every part of it is covered with little glittering swellings which shine in the sun like minute ice crystals. The swellings contain a store of water, or rather of colourless sap, which makes it able to exist in dry places. Dr. Ludwig says that a torn-off branch remained quite fresh for months on his study table. It is probable that these peculiar pearl or ice-like swellings also focus the sunlight, acting like lenses, upon the inner part of the leaf, but that is not as yet fully understood. There are two grasses, growing in the desert, which are of some value; both are called Esparto or Halfa. They are very dry, woody, or rather wiry grasses, especially common in Algeria, Tripoli, and also found in Spain. One of them, Stipa tenacissima, grows in rocky soil in Morocco, Algeria, and Tripoli. The Arabs search for it in the hills, and dig it up by the roots; they then load their camels with the grass and bring it to the ports whence it is sent to London or other places. A very good and durable paper is made from it, and ropes, mats, and even shoes are also produced from the fibre. Part of the "esparto" is, however, furnished by another grass (Lygeum sparteum). The natives sometimes tie 137 a knot in a halfa leaf, which, according to them, cures a strain of the back. The Stipa is also used as fodder, but it is not nutritious and is indeed sometimes dangerous. In one year Britain imported 187,000 tons of esparto, worth nearly £800,000. The yield is said to be about ten tons per acre. Another very interesting plant at Tripoli and in the North African Desert generally, is a sort of broom, the Retama (Retama Raetam). It is not very unlike the common broom, but has long, leafless, whip-like branches covered by bright pink-and-white flowers. It can often be seen half submerged in waves of sand, and struggling nevertheless to hold its own. As it has no leaves its loss of water is very much kept down. This is the Juniper of the Bible, and it is still used for making coals. The length of the roots is very great in most of the broom-like, "hedgehog," and other plants. A quite small plant not more than six or eight inches high will have a root as thick as one's thumb. Even at a depth of four or five feet below the surface its root will be as thick as the little finger, so that the root-length is at least twenty times the height of the visible part above ground. These thirsty roots explore the ground in every direction, and go very deep downwards in their search for water. Another very interesting plant in the Egyptian Desert is Citrullus Colocynth, from which the drug colocynth is prepared. The great round yellow-green fruit and finely divided bright green leaves may be seen lying on the sand. It remains green all the summer, but appears not to have any particular protection against loss of water. It is always supplied by its roots with underground water. If a stem is cut through it withers away in a few minutes. This is found also in Asia Minor, Greece, and Spain. The pulp of 138 the fruit contains a strong medicinal substance; it is a drastic purgative, and in overdoses is an irritant poison. This was probably the Wild Vine or gourd which the young prophet gathered, and which produced "death in the pot." He probably mistook it for a water melon. It is still plentiful near Gilgal (2 Kings xiv. 38-41).[64] Below the surface of the earth, of course, there is not nearly the same dryness or danger of losing water, so that there are often a great number of bulbs, tubers, and the like hidden in the soil. There they wait patiently, sometimes for a whole year or even for a longer period. So soon as a shower of rain falls they start to life, push out their leaves, and live at very high pressure for a few days. After a shower of rain, the Karoo in South Africa, for instance, is an extraordinarily beautiful country. There are bulbous Pelargoniums, a very curious leafless cucurbitaceous plant (Acanthosicyos), hundreds and thousands of Lilies, Irids, and Amaryllids. A single scarlet flower of a Brunsvigia can be seen more than a mile away! These tender and delicate, exquisitely beautiful bulbs flourish amongst the succulent Euphorbias and Mesembryanthemums, between the hedgehog-like thorny plants and the woody little densely-branched mats of the permanent flora. The rain stimulates even these last to put out green leaves and flowers, but their time comes later on, when by the return of the usual drought every leaf and flower and the fruit of every bulb has been shrivelled up, turned into powder, and scattered in dust by the wind.[65] Then the Karoo becomes unlovely, desolate, and barren-looking, with only its inconspicuous permanent plants visible. 139 The above description applies to bulbs and perennial plants with underground stores of food. Yet these are by no means the only plants which manage to exist in the Egyptian and Arabian desert. After a shower of rain a whole crowd of tiny annuals suddenly develop from seed; they come into full flower and have set their seed before they are killed off by a return of the desert conditions, when the effects of the rain have died away. These plants are not really desert plants at all, for they only grow during the short time that it is not a desert. They are like the Ephemerid insects which live for a summer day only. Nor is it only in Egypt that we find such ephemerals. Mr. Coville found them in the Colorado desert in North America. The plants are quite different, but similar conditions have brought about an entirely similar mode of life on the other side of the globe! In Colorado they seem to be much influenced by the quantity of rain. Mr. Orcutt, after the great rain of February, 1891, found plants of Amaranthus (allied to our Love-Lies-Bleeding), which were ten feet in height, but in 1892 he found specimens of the same in the same place only nine inches high, though they were perfect plants and in full flower; in this last year there was only the usual very scanty rainfall. It is, however, in deserts when man has set to work and supplies water and strenuous labour, that the most wonderful results appear. The whole of lower Egypt, Babylon, Nineveh, Damascus, Baghdad, Palmyra, and other historic cities, show what the desert can be made to produce. As one slowly steams up the Nile from Philae or Shellal towards Wady Halfa, there are places where the brown, regular layers of the Nubian Sandstone form cliffs which advance almost to the water's edge. Yet there is a narrow strip of green which fringes the water. 140 It is upon the actual bank itself, which is a gentle slope of ten to fifteen feet, that Lupines, Lubia beans, and other plants are regularly cultivated. This narrow green ribbon remains almost always on each bank. Where the cliffs recede, one notices a line of tall, graceful date palms, mixed occasionally with the branched Dôm palm (the nut of which yields vegetable ivory).[66] Tamarisks, conspicuous for their confused, silvery-green foliage, can be noticed here and there. The Acacias are common enough, and sometimes one of them is used as a hedge. It is a spreading, intricately-branched little shrub, with very white branches and stout curved thorns. If one lands and strolls along the banks below the palm trees or amongst plantations of barley, wheat, or lentils, one sees the native women in their dark green robes gathering fruits or digging. Goats and donkeys are tethered here and there. There are sure to be castor-oil bushes. Small but neat pigeons, with a chestnut-coloured breast and bluish-banded tails are perching on the palms or acacias, and utter their weak little coo. The air is suffering from the horrible creaking and groaning of a "sakkieh" water-wheel. This is made entirely of acacia wood, and is watering the plantations. Sometimes it seems like a crying child, then, perhaps, one is reminded of the bagpipes, but its most marked peculiarity is the wearisome iteration. It never stops. One of them is said to supply about 1-1/2 acres daily at a cost of seven shillings per diem. Exactly the same instrument can be seen pictured on the monuments of Egypt 4000 to 5000 years ago. The "shadouf" is of still older date. This is a long pole bearing at one end a pot or paraffin tin and balanced by a mass of dried mud or a stone. All day long a man 141 can be seen scooping up the coffee-coloured water of the Nile and pouring it on the land for the magnificent sum of one piastre a day. Where not irrigated, the soil is dry and parched and can only carry a few miserable little thorny bushes. The entire absence of grass on the brick-like soil has a very strange effect to English eyes. The Date Palm, however, requires a little respectful consideration. If one enters a thick grove and looks upwards, the idea of Egyptian architecture as distinguished from Gothic and others is at once visible. It has quite the same effect as the great hall of columns near Luxor. The numerous stems ending in the crown at the top where the leaves spring off was quite clearly in the minds of the architect at Karnak and other temples. It goes on bearing its fruits for some two hundred years, and begins to yield when only seven years old. It revels in a hot, dry climate with its roots in water, and seems to require scarcely any care in cultivation. Yet during the first few years of its life it is necessary to water the seedling. A single tree may give eight to ten bunches of dates worth about six shillings. Generally it is reproduced by the suckers which spring out from the base of the tree. Dates make a very excellent food, not merely pleasant but both wholesome and nutritious. Sometimes toddy is made by fermenting the sap, but this is a very wasteful process, as it is apt to kill the tree. The stones are often ground up to make food for camels. The feathery leaves are exceedingly graceful. When quite young they are not divided, but they split down to the main stalk along the folds, so that a full-grown leaf affords but little hold to the wind. 142 In some parts of Egypt, as for instance at Mariout, which is some fifteen miles from Alexandria, the wild flowers are probably more beautiful than anywhere else in the world. Amongst the corn and barley, which can be there grown without irrigation, masses of scarlet Poppies and Ranunculus are mingled with golden-yellow Composites, bright purple Asphodels, and hundreds of other Eastern flowers. The result is a rich feast of colour indescribable and satisfying to the soul. So that these deserts under the hand of man rejoice and blossom as the rose. Why is it that, as Disraeli has pointed out, civilization, culture, science, and religion had their origins in the desert? The answer is not difficult to see: for there is a dry, healthy climate; the severe strain of a long day's journey is varied by enforced leisure, when, resting at his tent-door, the Arab is irresistibly compelled to study the stars and to contemplate the infinite beauty of the night. It seems also to have been in the desert of the old world that man first learnt to cultivate the soil. In fact, it was only by irrigation on great tracts of alluvium, such as were furnished by the Nile and Euphrates, that the enormous populations of Egypt, Babylon, Nineveh, and the other great monarchies could be maintained. So that city life on a big scale first developed there. 143 <div style="break-after:column;"></div>

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