V

FLORA

The flora of Bornu corresponds exactly to the geological formation and climatic conditions of the country.[143] The usual appearance of the country is that of a tree-covered steppe, which extends south of the border-line of the regular summer rains over the vast plains of the interior of Africa from somewhat north of 8° of north latitude, from Senegal to Cape Guardafui, east of the great Central African lake and reaching southwards as far as South-East Africa. The character of this steppe is dependent on the predominance of deciduous plants, mostly belonging to the order of Leguminosae, and of many thorny trees and bushes, which very gradually give way on the borders of the country, according to local conditions, to representatives of the flora of the desert, of the damp tropical uplands or of the primaeval forest district, or else are found intermingled with them. Whilst Bornu shows in the north over a wide extent somewhat more luxuriant examples of species belonging entirely to the flora of the desert, on its own side also it spreads plants peculiar to itself pretty far into the south of the Sahara, but it lacks representatives of the above-mentioned grass-lands and primaeval forest flora owing to the predominance of evergreen trees and the appearance of epiphytic vegetation. Nowhere in Bornu can one find the dark-green forests with their hot-house humidity and tree-loving ferns, orchids,[144] and begonias, with pandanacea and different kinds of climbing calamus, with raphia- and oil-palms, which in dense lines edge the water-courses of the grass-lands lying not much further south. Of plants which are peculiar to such districts, the banana is only to be found at one place in the country, and that curiously enough is at Zinder, in the north-west corner of the country, whither it must evidently have been introduced from outside.[145] The raphia-palm, Raphia vinifera, and different varieties of paw-paw[146] first appear on the southern edge of the Mandara mountains, which lie scattered to the south of the tenth parallel of north latitude, and only one variety of Ceiba pentandra, which is indeed stunted enough in comparison with the specimens of giant Ceiba (Bombax) of the West African primaeval forest, is to be found here and there in the neighbourhood of the water-courses. There are indeed the trees of the Ceiba species, which, in contradistinction to the evergreens, shed their leaves in the dry weather—even in the primaeval forest. It appears rather strange that none of this kind of vegetation occurs along the course of the Lower Shari, which is always full of water, although it is plentifully represented at the sources of that river, especially the Gribingi,[147] and although it extends for a short distance down-stream close to the banks. The reason of this phenomenon may perhaps be sought for in the fact that the long and intensive dry weather of Bornu, and also of the Lower Shari country, is not favourable to this kind of vegetation. This is analogous to the similar phenomenon on the Upper Nile, where the plant formation of the hot damp countries where the river rises extends through districts which get drier and drier as one proceeds northwards, but cannot advance at all after the latitude of Khartum.

The sole or at any rate predominant landscape as regards Bornu, so far as it depends on the flora, is just this tree-studded steppe.[148] Even the trees are in unison with this steppe; if they do not belong to the prevailing species of acacia, they are at any rate of a habit in accordance with them. They are in general low, stunted and twisted, with deep roots and wide-spreading crowns, not higher than the trunk of a twenty-year-old oak sapling; only along the water-courses and where a deep layer of ‘humus’ soil exists do they reach a more considerable height, but even in the most favourable spots they do not much exceed 25 metres. The density with which the trees are planted depends also on the condition of the soil. Generally the trees stand in high steppe-grass at such long intervals that their crowns hardly touch, then the landscape reminds one of the extensive fruit-tree plantations of the north. The better the soil is, the closer stand the trees and thus form dense wide-spreading forests, often tangled with creepers, as for example in the riverain district of the Lower Shari from Karnak to Lake Chad.[149] In other places, especially on the granite slopes of the hills that jut out into the Bornu plain, the trees occur so far apart, that the landscape comes to show a great similarity with the slopes of the Sierra Nevada covered with sparse ilex trees which dip down to the Rio Genil in Southern Spain. In fact, where the true tropical trees, such as the palm and fig species, or the strange-looking ‘kuka’ (Adansonia) are wanting, the general impression of the flora is quite that of Northern Europe. Often, especially in winter when the ground is covered with fallen leaves, one can find places that at once recall the tree-bordered river valleys of the low-lying plains of North Germany in autumn. Localities which give a regularly tropical impression are at all events not in the majority, and the inspired descriptions of tropical luxuriance which Nachtigal gives on his first acquaintance with these parts, originated, as he himself has to admit, from the impression of dissimilarity between the Chad countries and the Sahara through which he had just struggled.[150]

By far the largest number of characteristic trees and bushes are naturally of such a stamp as are suited to the conditions of the country. The arrangements designed for the preservation of species are the thorny spikes for defence against annihilation by things that feed on them or for protection against drought during the winter months. Most of the trees shed their leaves in the dry weather, but those that do not, possess a quantity of thick leathery foliage or fine feathery leaves, succulent twigs, tendrils with tough outer fibre or thick cork-like bark. On the shea-butter trees, Butyrospermum Parkii, and the ilia-acacia, Burkea africana, and especially on the timber found in Southern Bornu, this thick cork-bark is to be observed, serving at the same time as a protection against the ‘bush’ fires.[151]

Soon after the beginning of the dry weather the high grass is quite dry, and affords ample material for the ‘bush’ fires that now commence. The trees and bushes, sticking out of the burnt, ash-covered soil with their bark all charred, offer then a melancholy spectacle. This may make them appear as if quite dead, but as a matter of fact the bark, of which only the outer layers have been burnt, has been able to protect the sap so well, that just before the beginning of the first rains tree and bush put forth fresh leaves and twigs or even stand dressed in full bloom.[152] About the beginning of January the Leguminosae begin one by one to bloom, and shortly afterwards the other trees and shrubs follow suit, so that the ‘bush’ is soon pervaded with an overpowering perfume.

A few species of trees form a remarkable exception, for it is just 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.

Typical specimens of ever-increasing size now appear of the giant of the African tropical ‘bush’, the Adansonia digitata, or ‘Kuka’ as the Kanuris call it. It is, indeed, distributed all over the country,[192] for the most part in the neighbourhood of the towns, where its fibre is made into rope and its young leaves are valued as a vegetable; but it is not till one gets to Southern Bornu that one meets with examples truly characteristic of the species, the bulk of whose trunks is out of all proportion to their height; at Issege on the Yedseram there are trees measuring fifteen metres and over in circumference. The Adansonia, like the Ceiba, is perfectly bare during the dry weather, but the leaves appear with the first rains and are soon followed by the big white flowers on their long pendent stalks. Another true native of the tropics is the Deleb palm, Borassus aethiopum, which is almost entirely absent from Northern Bornu,[193] but now sometimes singly, sometimes in groups, vies in height with the other giant trees of the southern districts. Its trunk, straight as an arrow but thickening to a cigar shape in the upper half and crowned with compact fan-like leaves, forms a most effective ornament to the landscape. The trunk furnishes an excellent weather-proof timber, and the big fruit, of a brilliant orange yellow, is eaten all over the country, but its somewhat acid taste does not correspond to the expectations raised by its delicious smell, which resembles that of a pineapple. While the Deleb palm is not found in certain districts—often a day’s march apart—yet in other places, as in the Musgu country on the lower Logone, it appears in great numbers and in magnificent serried rows, generally, indeed, in the immediate neighbourhood of the towns.[194] To the fig species of this district belongs the tree known as ‘Ganyi’, with large leathery leaves: it owes its name to the triangular incisions which are regularly found on its bark, and which are caused by the natives tapping it to obtain caoutchouc. But it is impossible that the quantities obtained of this much sought after substance can be large, for the tree is only met with here and there quite sporadically, especially in the denser parts of the ‘bush’ overgrown with ‘vitis’ creepers as thick as a man’s arm along the rivers in Southern Bornu.[195]

When the ‘bush’ borders on the rivers the shrubs of the undergrowth are thickly covered with the delicate green tendrils of the Sapindaceae, Cardiospermum halicacabum, which is ubiquitous all over the Sudan. This creeper, distinguished by its dainty leaves and bladder-like fruit, is to be met with quite regularly on the steep banks of streams. In places where it is possible for the river to overflow its banks, other kinds of plants which prefer a marshy or, at any rate, a damp soil, have established themselves, such as various shrubs of Rubiaceae belonging to the Sarcocephalus species, easily distinguishable by their white globular blossoms.[196] The swampy ground is every now and then covered with a thick aromatic carpet having a scent something like thyme, composed of one of the Labiatae belonging to the Ocimum species (perhaps Ocimum viride?); and wherever pools are able to form, the blue star-like flowers of the Nymphaea Zanzibariensis gleam once more together with the floating bright green buds of the inevitable Pistia stratiotes.

The nearer one gets to the Bornu boundary, the richer and more various is the flora. In the neighbourhood of the big rivers, indeed, the character of the landscape alters but little, although even here one or two kinds of trees appear that were hitherto unrepresented. Among these are to be reckoned the Celtis integrifolia, which Chevalier mentions on the middle Shari,[197] as well as the Khaya senegalensis, whose towering trunks attain magnificent proportions on the upper Yedseram, and furnish the finest forest scenery of this region. The Khaya, which has already been rooted out over a large extent of country in West Africa, is of importance because it furnishes part of the supply of West African mahogany. One of the most botanically remarkable shrubs of this district is a true willow, Salix, which fringes the banks of the upper Yedseram in company with the Mimosa pudica, and apparently belongs to the same species as the latter, forming regular thickets on the Benue near Lau.

Very striking, however, is the change in the flora in the true ‘bush’, especially in places where the first traces of granite appear. Besides the Leguminosae, which have hitherto been absent, the Cisalpiniaceae become prominent, forming by far the larger number of the species of trees of this region, especially the Combretaceae, which are so characteristic of the hill country lying to the south. Everywhere one now meets the Combretum species, the Anogeissus leiocarpa, and the Terminaliae, the chief trees of the Southern Bornu ‘bush’. By far the commonest of these is the Terminalia Schweinfurthi, the shape of whose trunk and branches might easily cause it to be mistaken for a fair-sized oak, though its big smooth-edged leaves have somehow quite a strange look. Differing from the other low-growing shrubs owing to its maple-like leaf is the Sterculia tomentosa—closely related to the ‘kola’ tree, Sterculia acuminata,[198] which is not found in Bornu—and also, owing to its pronounced tendency towards cork formation, the well-known Burkea africana. At first only appearing sporadically, but afterwards in ever-increasing numbers, one now meets two trees which play an important rôle in the Sudan, viz. the Parkia biglobosa of the Leguminosae and the Butyrospermum (Bassia) Parkii, or shea-butter tree, of the Sapotaceae. With its dainty feathery leaves and the strange shape of its blossoms, the former is an ornament of the granite hills, the foot of which is its favourite situation. In early spring the velvety dark blood-red blossoms, always in pairs, appear on long hanging stalks; in shape and size they resemble a billiard ball, and are out of all proportion to the tree’s delicate feathery leaves. From them develop, in the course of the summer, bunches of considerable-sized pods whose seeds form the ingredients of the ‘dadawa’ cakes, which are relished all over the Sudan and sold in every market; they have a nauseous smell, however, and are only digestible by a negro’s stomach. Much more important than the Parkia is the Butyrospermum. It is a moderately tall tree, its bark is full of cracks, and its foliage reminds one at a distance of that of the Spanish chestnut, or, still more, of that of the Mangifera indica; it bears a fruit whose large single kernel is akin to the mango, and produces a vegetable oil which keeps well and is put to various uses, and which has become of ever-increasing importance as an article of export. The fruit has a pleasant taste resembling a date.

This district also is particularly the home of the Candelabra euphorbia, known as ‘Garuru’, which in many respects resembles the American Cercus species and in shape is also like the dragon-tree of Teneriffe; on granite soil it reaches a height of ten metres and is crowned by extraordinarily thick foliage. These Succulenteae are distributed all over Bornu, and are found sporadically even in the plains, but they are never entirely absent from any of the pagan villages, which lie at the foot or half-way down the slope of the isolated hills, for they possess qualities which render them of great use to the natives. Firstly, the thorn-protected branches furnish the best imaginable live hedge, and, secondly, the milky juice that flows from the slightest incision is one of the chief ingredients of their arrow poison. The small yellowish-green blossoms, which differ hardly at all from those of the European spurge, appear towards the end of the rainy season.

The open ‘bush’ of Southern Bornu produces grasses that surpass in height and luxuriance anything similar from more northern landscapes. In the great Marghi Forest, east of the Yedseram, a favourite haunt of big game, the grass—in places where the water has dried up—reaches such a height that it covers an elephant standing erect, and only the long neck of the giraffe reaches above it. At the flowering time the stalks, which can hardly be avoided when marching along a narrow path, send out at the slightest concussion clouds of yellow pollen, which is troublesome to man and beast alike. One can understand that this grass, which itself reaches the very tops of the Terminalia, does not allow other plants to come up. Only where in damp places short-stalked grasses form natural pastures for the game, variegated plants appear—at least, at the beginning of the rainy season—amongst them numbers of a sort of Amaryllis with big white and purple striped flowers and beautiful tall ground orchids, such as the lilac-blossomed Eulophia (Lissochilus) dilecta and Lissochilus lindleyanus, with similar clusters of golden-yellow blossoms.

The highlands of Mandara and the scattered granite masses, which make the landscape of Southern Bornu so attractive, form at the same time sort of islets of flora, which show unmistakable differences from the surrounding plain. Many remarkable kinds of plants only occur here—these rocks are an El Dorado for the botanist—and never stray down into the plain. It is noticeable that it is near the perennial springs, which gush out on the slopes and at the foot of these isolated hills, that one finds the only ferns in Bornu, mostly pretty varieties of Adianthum, which, besides, are identical with those of Adamawa. But amongst the representatives of the tree flora also many interesting species are to be found. Thus the granite rocks north of Uba are thickly overgrown with a species of fig-tree, the ‘Bidjage’, from which Barth says that the natives prepare their arrow poison.[199] The ‘Bidjage’, Ficus populifolia, is similar in the shape of its leaves to the ‘Ngabore’ found near Lake Chad, only it has striking light grey-green leaves, but its qualities are certainly not more poisonous than those of any other species of fig.

The cultivated plants of Bornu are drawn from a wider range than are the wild ones. The majority of the former belong to species which are cultivated all over Africa south of the tropic of Cancer, or are such as are distributed over tropical countries throughout the world.

Of the Graminae cultivated in Bornu for grain by far the most important are the Andropogon species (Sorghum holcus) and the bulrush-headed millet, Pennisetum (Penicillaria), with their different varieties. In comparison with them all other kinds of grain play a quite subordinate rôle—at least at present. For the cultivation of the Andropogon species on the one hand, and of the Pennisetum species on the other, Barth assumes, and Nachtigal also lays down certain boundaries depending on the composition of the soil.[200] But this assumption is not to be taken literally, for, especially in view of the continuous shifting of population, the area of distribution of the grain-stuffs has likewise been shifted in the last few decades.

The best known Pennisetum is the ‘Dukhn’, Pennisetum spicatum (typhoideum) with bulrush-like heads, which is excellently suited for cultivation in the sandy plains of Bornu. Sown at the beginning of the rainy season, the ‘Dukhn’ only takes two months to reach full maturity. The grain grown on the finer and moister land is the ‘Durrha’, Andropogon sorghum—called in Bornu ‘Ngafeli’—which is distributed over the whole of tropical Africa and part of southerly subtropical Africa and over wide districts in Asia; it is sown at the same time as ‘Dukhn’, but ripens about a week later than the latter.[201] Besides the ‘Durrha’ itself two varieties are cultivated, the ‘Sabadu’,[202] Andropogon saccharatum, and above all the ‘Massakwa’, Andropogon cernuum, a grain which is grown in water, and which, sown towards the end of the rainy season on swampy soil, is transplanted after fourteen days at slight distances apart, and after only ten or twelve weeks with the help of the heavy dews is ready to cut.[203]

The grain which has its proper home in this region, the wild rice, Oryza punctata, is little valued; it grows wild in the swampy plains, exposed to floods in the rainy season, between the Shari and the Mandara highlands,[204] forms there the chief food of the elephant, but is also gathered by the poorer classes of the population. Rice is also always cultivated here and there in small quantities, as, for example, on the southern shores of Chad.

Somewhat more commonly one meets with plantations of maize, Zea Mays,[205] which is often cultivated in well-watered parts of Bornu which have a fertile soil rich in mould;[206] on the other hand, the European cereals, barley and wheat, are very seldom grown and then only with artificial irrigation and as a dry weather crop.[207] The three last-named kinds of grain are regarded solely as delicacies and are scarcely to be considered as forming part of the people’s food-stuffs. Similarly tubers are only partly acclimatized in Bornu and are only cultivated sporadically.

The tubers consist of the following: Colocasia antiquorum, Dioscorea batatas, Manihot utilissima, and Ipomoea batatas, all lately introduced for the first time and gradually imported into Bornu from the south. From the north the onion has been brought into the country by the Arabs. It grows excellently on the banks of Chad and reaches an extraordinary size. But there are at any rate some plants long established in Bornu which are cultivated as vegetables, such as the ‘Karass’, Hibiscus esculentus, whose pods furnish a slimy but pleasant-tasting vegetable. The mallow, allied in habits to that grown in the peasant gardens of Central Europe, and with flowers similar to those of the cotton-plant, which is likewise its relative, is to be found in almost all the villages of Bornu. Indigenous likewise to the Sudan is the giant pumpkin, Cucurbita pepo—or Cucurbita maxima according to Barth[208]—which thrives everywhere and often covers the houses with thick tendrils and in the flooded districts of Lake Chad stretches over vast areas, which in the dry weather one can distinguish even at a distance by the big white gourds. Sesame[209] also, Sesamum indicum, equally esteemed both as a vegetable and as an oil-producing plant, has long been cultivated in Bornu; its thimble-shaped white or red flowers are regularly to be found in the neighbourhood of the villages. A more debatable question is the origin of the two varieties of ground-nut which are distributed over almost the whole of tropical Africa; their scientific names are Arachis hypogaea and Voandzeia subterranea, and they are widely cultivated both as vegetables and for the production of oil; the fact that each has a name of its own in all the languages of the country, argues that they found an entrance into the very centre of the Sudan at least a long time ago. Of true pod-bearing plants two are cultivated in many places, a bean, the Phaseolus, and a variety of Dolichos.[210] From Asia have doubtless come the tomato, Solanum lycopersicum, and the cress, Lepidium sativum,[211] which are both grown in the gardens of Central Bornu.

Besides these quite a number of wild plants furnish both vegetables and fruit. Bornu is extraordinarily poor in trees or bushes that are cultivated for the sake of their fruit. The only fruit-tree of this kind really worth mentioning is the paw-paw,[212] Carica papaya, which, however, does not extend to the northern parts of Bornu. The Aurantiaceae fruit-trees, which are so widely distributed elsewhere in similar tropical and subtropical countries, are only represented by a few scattered lime-trees—obviously introduced by the Arabs from the North—in the gardens of the bigger towns of North and Central Bornu, such as Zinder, Kukawa, and Dikoa.[213] It is equally seldom that one meets with true spice-plants in Bornu. It is not till one gets to the southern districts that one finds that the capsicum-pepper, imported from Adamawa, has here and there obtained a firm footing.

The predilection of the natives for narcotics, some of which are hardly ever found growing in the country, while others on the contrary are extensively cultivated, is an argument that the former were first introduced, while the latter had already long belonged to the Central Sudan, very probably even at the time of the discovery of America.[214] The most important, in fact almost the only narcotic cultivated in Bornu, is tobacco, which is grown everywhere—especially in dried-up sandy river-beds—but above all in Musgu country.[215] From the proofs which he adduces there is more than usual to be said for Barth’s view that the species of tobacco grown there is indigenous to that region.

With much more justice might it be contested that those plants were indigenous in Bornu, for which there might be adduced the possibility of introduction from the East contemporaneously with the extension of Islam. To these belong indigo, Indigofera tinctoria, cultivated for the production of dye, and henna, Lawsonia inermis. The former is grown especially in the southern districts for the production of the indispensable dye for dyeing blue cloths; henna, used for dyeing the finger-nails red, is grown in smaller quantities in all Mohammedan districts of Bornu.

With regard to cotton, by far the most important and almost the only cultivated plant applied in Bornu to textile uses,[216] it is certain that it was not brought to the Central Sudan from the New World, even if one regards it as an immigrant. Rohlfs expresses himself as follows about cotton: ‘It is quite certain that the cotton-shrub is to be regarded as a plant indigenous to Africa; at least, this theory is supported by its wide distribution over the African continent, as well as by the abundance of words for cotton which are to be found in all the negro kingdoms. The word ‘Kalkutta’, which the Kanuris use, appears to be derived from the Arabic in the same way as the German ‘Kattun’ (and the English ‘cotton’).[217] Barth also mentions that in the time of Edriss Aloma cotton was already cultivated in the Sudan,[218] at a time, too, when its introduction from America was at least very unlikely. The cotton cultivated in Bornu and Adamawa is the perennial variety classified by Passarge[219] as Gossypium arboreum, which in many places, such as Ngornu on the shores of Chad, reaches a height of over two metres. It is cultivated in Bornu wherever the influence of Islam prevails and where the majority of the people wear clothes.[220] Its favourite situation is the banks of rivers rich in mould and not too much exposed to floods and the vicinity of loamy low-lying ground strongly impregnated with sand.

Amongst other plants of importance which are grown for industrial purposes is the Cucurbita species, from which are manufactured by far the largest number of household vessels except those used for cooking. Besides the well-known Cucurbita pepo, which not only furnishes calabashes but also serves for the manufacture of floats, there is also the bottle-gourd, Lagenaria vulgaris, particularly trained as a creeper on houses or fences. Its fruit is of very many different shapes and this has led to different designations of the plant; however, it is merely one and the same species assuming various forms.