ON DESERTS
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.
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 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]
[61] Darwin, _Naturalist's Voyage round the World in the Beagle_,
p. 387.
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.)
[62] Schimper, _l.c._, p. 674.
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 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]
[63] Schimper, _l.c._, p. 653.
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.
[Illustration: 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.]
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 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 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 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]
[64] Ridley, _Pharmaceutical Journal_, May 19th, 1900.
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]
[65] Scott Elliot, _Trans. Bot. Soc. Edin._, vol. 18, p. 243.
Then the Karoo becomes unlovely, desolate, and barren-looking, with
only its inconspicuous permanent plants visible.
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.
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.
[66] Used to make billiard balls.
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 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.
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.