during the rains that they are leafless and seemingly dead, yet as soon
as the rains are over they put forth new leaves and reach their greatest
luxuriance in the middle of the dry weather.
After the first tornadoes the ash-covered earth begins to cover itself
with a thick green turf, which gives the landscape a park-like
appearance, and from it spring in a few days great quantities of
variegated Ranunculaceae and lilies, followed soon afterwards by the
flowers of such trees and shrubs as have not already come into bloom.
When the flowers come into view, the season corresponds somewhat to the
spring-time of Central Europe, and a similar state of things continues
for the following months; by June or July the leaves are all fully out,
and in October, at the end of the tornado season, the latest fruits have
ripened. Among the fruit-bearing trees that grow wild are some that are
made use of by the natives; as regards the greater part of those
mentioned by European travellers as being useful, there are very various
reports. Barth, who seems to be by no means dogmatic, praises them for
the most part, but Denham expresses himself less favourably, and the
greater part of this traveller’s observations come pretty near the
truth.[153] At all events the really pleasant-tasting fruits are quite
rare in the ‘bush’.
The flora of Northern Bornu is also strongly influenced by the Sahara,
which pushes forward representatives of its own here and there far
beyond its borders. In addition to the different species of thorny
acacia, similar to each other in habitat, which after reaching a certain
age generally have umbrella-shaped crowns, and which are so generally
characteristic of all the sterile districts of Africa, the two regions
have quite a number of plants in common.[154] The two most striking,
which one meets almost everywhere, are the Zizyphus species and the
oschar, _Calotropis procera_ (called by Barth _Asclepias gigantea_). The
wide distribution of the Zizyphus species is explained by its
suitability to all kinds of soil and the usefulness to mankind of its
fruit, which is mealy tasting and slightly sweet, and for the sake of
its branches to form thornhedges as a protection against beasts of prey.
The Zizyphus is found northwards as far as the Mediterranean
countries[155] and southwards as far as the boundaries of the Sudan
climate. The two varieties principally met with in Bornu are those
called by the natives ‘Kurna’ and ‘Magalia’, _Zizyphus Jujuba_ and
_Zizyphus spina Christi_ respectively. The hardy ‘Magalia’ may take the
form of magnificent shade-trees, especially in sandy soil, and
constitute in uninhabited places thick thorny copses, which lead one to
conclude almost with certainty on the presence of former settlements.
The ‘Oschar’, far the tallest of all the Asclepiadae,[156] owes its wide
distribution to the seeds, provided with silky floating fluff,
distributed by its fruit, which is shaped like a small bladder and is
larger than a man’s fist. These plants, which are in their fullest
foliage towards the end of the dry weather, are to be found all over the
Sahara[157] in favourable localities, and form on the sand-dunes of the
south-west shore of Chad wide-spreading bushes,[158] whose grey-green
leaves give to the landscape an impression of uniformity and melancholy,
and extend from here even as far as Lagos.[159]
Of widely distributed plants belonging to the two regions in common, one
of the most remarkable is the dum-palm, _Crucifera thebaica_, the sole
representative of its genus, whose trunk is divided into several
branches. They prefer a soil that attracts the surface water, and are to
be found from the oases of the Central Sahara to far into Adamawa—though
here indeed only very scattered; some splendid examples flourish
especially at Ngornu, on the shore of Lake Chad. South of this region it
is very rare. According to Barth the fruit may be used in large
quantities for food,[160] but on the other hand the same traveller
points out that the low-growing dum-bushes are a hindrance to
agriculture.[161] In fact, between Kukawa and Ngornu one finds wide
stretches so thickly studded with the young plants of this palm which it
is so difficult to eradicate, that one is reminded of the plains of the
Mediterranean littoral overgrown with ‘chamaerops’.[162]
The date-palm also, the most characteristic tree of the Sahara, is to be
found dispersed in single examples all over Bornu, and specimens
transplanted by man may even be seen in the middle of Adamawa. But it is
seldom or never that it bears fruit in Bornu; the summer rains do not
suit it, any more than they do the camel, and it is a proof of the
desert character of certain of the sandy valleys of the neighbouring
country of Kanem, that the date-palm flourishes there in full luxuriance
and bears abundant fruit.[163]
Belonging likewise to both regions, but confined within narrower limits
and generally not extending farther south than the latitude of Kukawa,
there are certain plants found in Northern Bornu which are partly used
for the production of salt. The most striking of these is the peculiar
‘tundub’, _Capparis aphylla_ (_sodata_),[164] found in the same parts as
the dum-palm, the ‘ethel’, _Tamarix articulata_,[165] the ‘retam’,
_Retama spec_—according to Barth _Spartium junceum_[166]—the _Salvadora
persica_, and the _Asclepias leptadenia pyrotechnica_.[167] Of these
only the ‘tundub’ and the ‘retam’ are to be found widely distributed in
Bornu. The ‘tundub’ is of importance in that the ashes obtained from it
furnish the natives with salt.[168] As a salt-loving plant it is only to
be found on soil impregnated with natron, and becomes rarer as the
percentage of the mineral necessary for it to thrive decreases. It does
not seem to reach farther south than Kukawa. The ‘retam’, one of the
European species of _Spartium_ or _Ulex_, similar to the Papilionaceae,
forms on the sand-dunes south of Maduari thick bushes taller than a man,
which give to the places where they are found quite a northern
appearance owing to its genesta-like exterior.
Other kinds of trees and shrubs which belong without any doubt to the
Sudan, have nevertheless in favourable localities extended their area of
distribution far into the Sahara. Among these is the ‘hadjlidj’,
_Balanites aegyptiaca_, whose name, like that of the _Crucifera
thebaica_, indicates a very wide distribution; with its dark-green
hanging boughs it presents a very striking appearance. Its fruit, called
‘bito’ in Kanuri, plays, according to Barth, an important part as an
article of diet among the natives.[169]
It is much more difficult to define the area of distribution of the
acacias than of the other well-known species of trees, because they
resemble each other very much in all countries, and because it is only
very insufficiently established to what species they belong owing to
their great multiplicity of form. The definite classification of the
various species of acacia found in these regions, which is impossible
without the possession of an ample collection of material—at present not
yet forthcoming—would be a task well worthy of the gratitude of
botanists. But the classification is the more difficult in that each of
the numerous books of travel, while multiplying the names given by the
natives to these trees, apparently assign them to different species. It
is always possible that the natives, on whom botanical peculiarities are
naturally lost, may assign the same name to similar species. One may
therefore assume with certainty that the Arabic word ‘talha’ is a term
applied to all species of acacia that exude gum arabic.[170] By ‘talha’
are especially meant the _Acacia ferruginea_ common all over Bornu with
its little unmistakable reddish-brown trunk and branches and its dark
golden blossoms,[171] the _Acacia stenocarpa_,[172] and the _Acacia
tortilis_,[173] widely distributed in North Africa. All these species,
whose ball-shaped little blossoms make their appearance during the first
months of the year, diffuse at that time an extraordinarily strong
perfume reminding one of the violet or the heliotrope. To the finest
species, which assume with especial clearness the umbrella-like form,
belong the _Acacia arabica_, found far from here even in Aïr, and
especially the ‘gawo’, _Acacia albida_. The ‘gawo’[174] is especially
remarkable for this reason, in that it strikes one from a distance by
the complete bareness of its greyish-white branches during the rains; it
is not till October that it puts on its feathery leaves of greenish-grey
and its blossoms that remind one of willow-catkins.[175] To be found all
over Bornu and stretching far afield towards Adamawa, it reaches giant
dimensions on the banks, rich in ‘humus’, of the River Yedseram, south
of Bama.
The steppe-forest of Northern and Central Bornu[176] is composed
somewhat as follows. Scattered among the acacias, which predominate, are
the above-mentioned species of trees—to which may be added in Central
Bornu the ‘dschochan’, _Diospyrus mespiliformis_—which, however, form
isolated patches in the acacia forest whenever the condition of the soil
is suitable. The commonest of these is the ‘hadjlidj’ (_Balanites_).
Next to this the most frequent is the ‘Kargu’ or ‘Kalgo’, _Bauhinia
reticulata_, belonging to the order of Leguminosae, a shrub found as far
as Munio and Zinder,[177] which, like the _Mimosa pudica_, is remarkable
for rattling at night its large leaves shaped like an inverted heart.
This shrub appears mostly in the form of brushwood, prefers a sandy
soil, and on the summit of the dunes along the shores of Chad replaces
in some parts the Zizyphus and the _Calotropis procera_, with whom it
also enjoys a joint tenancy. It is likewise as a brushwood shrub that
the _Gardenia Thunbergia_ forms sparse bushes, whose thorny branches are
covered in the spring-time with big snow-white blossoms, which first
open towards evening and then diffuse a strong penetrating perfume. The
branches of these trees and shrubs are often intertwined with the
parasitic loranthus, whose rather large honeysuckle-like trumpet-shaped
flowers probably misled Barth and made him mistake them for
orchids.[178] The loranthus with its fleshy grey-green leaves and
hanging tendrils often forms great bushes, whose masses of foliage may
quite obscure the green of the tree it clings to. Many other creepers
attain such luxuriance that the tree they overgrow completely disappears
beneath their masses. One of the most striking is the sappy cactus-like
‘digessa’, _Cissus quadrangularis_, in which the small leaves are
inconspicuous as compared with the evergreen and peculiar four-edged
tendrils. According to Rohlfs, this plant, which is widely distributed
all over the country, is one of those from which the natives prepare
their arrow-poison.[179] Besides the _Cissus_ there is a kind of ‘luffa’
which is worthy of notice; its fungus-like fruit on its withered
tendrils attracts the attention of the traveller in the dry weather from
a long distance.
The high ant-hills in the ‘bush’ are regularly carpeted with Capparidae
such as the _Cadaba farinosa_ and _Capparis tomentosa_. The latter
especially affords a peculiar sight in winter and early spring, when its
thorny semi-creeper-like tendrils are in bloom. The blossoms, to which
are attached numerous long pollen-vessels, attract—as do the
acacias—through their strong honeysuckle-like perfume the whole flower-
loving insect world and the metallic-coloured honey-birds.
Many trees in the ‘bush’, and especially those which prefer marshy
places or the banks of streams, are inclined to isolate themselves and
so form splendid clumps, solitary and circular, that give the landscape
quite a park-like appearance. To this category belongs especially the
tamarind, _Tamarindus indica_—in spite of its name indigenous to
Africa—which does not shed its dark-green feathery leaves even in the
dry weather and puts forth its orchid-shaped flowers in the winter. Its
fruit serves many medicinal purposes and when pounded in water makes a
refreshing beverage. Even commoner than the tamarind are the various
species of evergreen fig which Bornu harbours, each in individual
isolation; such isolation is grounded in their very nature. Though of
great variety in the form and size of their leaves, they all show in
their habits the same characteristics. Similar to its Indian relative,
the banyan, in the early stages of its growth it takes the form of a
semi-parasitic creeper, which shows a distinctly astonishing inclination
towards a spread both of roots and branches. Soon after it has
surrounded the tree that serves it as host with a many-meshed net, the
latter perishes; the inextricable tangle of wood forms a single trunk,
which, as branch and bough keep on sending out new roots, finally
supports of itself the giant arbour-like roof of foliage, composed of
the countless roots both thick and thin that in their turn struggle
earthwards. The milk-like sap of all these species exhibits in a dried-
up condition more or less of the elastic properties of caoutchouc; the
fruit of some species are edible. One large species, known in Bornu as
‘ngabore’,[180] with poplar-like blackish-green leaves, reaches
especially at Ulugo and other places on the south shore of Chad a height
of over twenty metres and surpasses all other shade-trees owing to its
density of foliage. Owing to its dark colouring it stands out sharply
defined from everything else during the dry weather and forms a striking
contrast to the uniform muddy grey of the villages. Of much less compact
shape is the equally widely distributed Bignoniaceae, _Kigelia pinnata_,
which is found as far as Kanem,[181] and to which the much-travelled
Hausas have assigned the name of ‘nono-n-giwa’ (that is to say,
elephant’s udders) on account of its sausage-like fruit, which is over a
foot long and hangs from a long stalk. It is very commonly found in the
middle of the towns. The walnut-like leaf of this tree also lasts
through the dry weather, during which appear its straggling dark-red
clusters of blossom.
The ‘bush’ in Northern and Central Bornu differs in one respect from
that of the southernly districts, in that the grasses which cover the
soil do not there reach the same great height; in sandy places the low-
growing prickly grasses called ‘ngibbi’, _Cenchrus echinatus_ and
_Pennisetum dichotomum_, predominate, of whose notorious seed-grains
Denham remarks: ‘These prickles may be considered one of the pests of
the country.’[182] The unpleasant burr-like adhesive seed-grains of
these grasses cling fast everywhere and are a regular plague both to man
and beast—in fact, the latter’s hair is often thickly matted with them.
Owing to the easy way in which these noxious weeds are spread, they at
present flourish all over the Sudan, wherever they are not kept under by
other plants. It is astonishing how the Bornu horses are able to eat the
_Pennisetum dichotomum_ without any ill results, nay, Barth goes so far
as to say that they will not thrive without it.[183]
The Graminae flora are always predominant also in the undergrowth, for
the herbaceous flowering plants only make their presence felt during the
spring. Frequently the often magnificent flowers appear long before the
leaves, and are either stalkless like those of a large Zingiberaceae, or
else push their heads only a little above the surface of the soil like
those of the strange _Amorphophallus_ species and other Araceae. To one
of these families perhaps belongs the bulbous plant eaten by the natives
and mentioned both by Barth and Rohlfs, under the name of ‘Katakirri’ or
‘Gadagér’, as being found in Southern Bornu.[184]
In the districts in which the ‘bush’ consists chiefly of elements which
belong also to the Southern Sahara, it experiences in places
interruptions of quite foreign appearance, namely, from the flora of the
shores of Lake Chad and from the desolate ‘firki’ flats.
Peculiar to the shores of Chad is the total absence of trees. This is
only to be explained by the great irregularity of the water-level of the
lake, which must be extremely unsuitable for steady yearly growth:
during the long-enduring inundations, which put everything under water a
yard deep for months at a time, those trees are bound to decay which
cannot thrive except in a position which is normally dry. On the other
hand, trees whose roots demand a copious supply of water, suffer from a
year-long drought and find no compensation in the downpour, abundant as
it is, of the short rainy season for the absence of water springing from
below.
The places where trees grow—especially on the west and south shores of
Lake Chad—mark the boundary of a zone of marsh vegetation poor in
species but nevertheless interesting. Besides the high grasses and the
_Mimosa pudica_, which is ubiquitous wherever there is water, there is
usually nothing but the papyrus and the ‘ambatsch’ or ‘marria’,[185]
_Aeschynomene (Herminiera) elaphroxylon_, both of them plants which,
owing to their simultaneous appearance in the ‘sudd’ of the Upper Nile,
seem to point to an earlier connexion at some time between the two
districts. The papyrus, which is also found in the brackish lakes of the
Munio country,[186] reaches in the swampy thickets of Chad the
considerable height of four metres, but it is overtopped by the
‘ambatsch’. As its name (_elaphroxylon_) indicates, the latter is of
unusually rapid growth—in fact, one gets the impression that the stem of
this giant plant, which is as straight as an arrow and often as thick as
a man’s leg, reaches its full height inside of a single year. As soon as
the water recedes from any place for any length of time the ‘ambatsch’
dies, and then the shore is covered far and wide with the dead trunks
overlaid with green creeping plants. The wood, when quite dry, has an
elder-like pith, but is nevertheless comparatively durable and
extraordinarily light—a log as thick as a man’s leg, and some seven
metres long, hardly exceeds one kilogram in weight—and is put to various
uses by the inhabitants of the shores and islands of Lake Chad. The
‘ambatsch’ as well as the papyrus, standing in some places a yard deep
in water, is generally thickly covered with the tendrils of a luxuriant
kind of _Ipomoea_, whose big purple trumpet-shaped flowers, mingled with
the golden-yellow butterfly blossoms of the ‘ambatsch’, at any rate
enliven what is otherwise a monotonous vegetation.[187]
Although the marshy district on the shore of Chad is favourable to
certain kinds of vegetation, yet the ‘firki’ flats appear to be without
any plant growth whatever, and thus give the landscape a rather
extraordinary appearance of melancholy. Although the ‘firki’ flats are,
in the rainy season at any rate, a favourable soil for water-loving
plants, and are in their nature fertile, yet they dry up so rapidly in
the late autumn that only quickly growing plants, without being able to
come to flower, can maintain themselves as long as the layer of loam
retains its humidity; but after that cracks in the soil soon appear and
cause the roots to dry up, so that all existing vegetation must
necessarily die down. Only where there is subterraneous water or
stagnant water-courses that are able to last out the dry weather are
there acacias, which in some parts of this region so bare of trees
furnish the only fuel, and are so stripped of their branches by the
natives that with their stunted shoots they exactly resemble at first
sight the pollard willows of the north. On the pools and water-courses
that do last out the dry weather are found in places the flora, which
appear also elsewhere in Bornu, of the smaller lakes and ponds,
principally consisting of the buds of the cosmopolitan _Pistia
stratiotes_, with its lettuce-like head and two kinds of water-
lilies—the _Nymphaea lotos_ with yellowish white, and the _Nymphaea
Zanzibariensis_ with sky-blue flowers.[188]
The farther one penetrates into the ‘bush’ towards the south-west, the
south, and the south-east, the oftener do new species occur and replace
by degrees the more northernly varieties. The ‘hadjlidj’ (_Balanites_)
next disappears from the forest and the acacias are relegated to the
sterile spots; only the _Acacia albida_ remain as numerous as ever, and
appear in ever finer specimens. On the other hand, the _Anona
Senegalensis_ makes itself noticeable amongst the undergrowth with its
grey-green aromatic-smelling leaves; it is one of the few wild bushes to
produce edible fruit. ‘Gonda-n-Kura’, as the wild paw-paw is called, is
usually known by a Hausa name as opposed to the cultivated ‘gonda’, as
the _Carica papaya_ is called in the Central Sudan. Along the streams
there is found a tree with dark-grey bark and leaves, not unlike though
somewhat larger than the horse-chestnut, which it also resembles in the
shape of its strong-smelling blossoms. It is the _Vitex cuneata_,
belonging to the Verbenaceae and locally known as ‘Ngalibi’. Ink is
prepared from its bark,[189] and its black fruit is used for food. Near
it are always found other kinds of trees, whose external appearance
gives the impression of regular tropical growth. Next to it is the well-
named silk cotton tree, _Ceiba pentandra_,[190] though it is indeed far
from reaching the size of those found in the primaeval forest; in
favourable spots, however, along the river-banks where the ‘humus’ soil
is plentiful, there are specimens which cause it to stand out as one of
the tallest trees of the district. Large trees of this species were even
used by the natives of the middle Shari as places of refuge during the
slave raids.[191] The soft silky fluff of the seed capsules is used all
over Bornu as stuffing for various articles. Its relative, the _Bombax
buonopozense_, is very seldom found near the _Ceiba_; the former is a
tree which can never be overlooked, owing to its big dark-red blossoms,
which stand out at a distance against the background of its scanty
foliage.