There are valuable plants on every continent. Civilized Europe no longer counts them. Mysterious Africa is no less largely and spontaneously favored with them than young America and the ancient territory of Asia.

The latter has given us the majority of the best fruits of our gardens. We have already shown how useful the butter tree (Butyrospermum Parkii) is in tropical Africa, and we also know how the gourou (Sterculia acuminata) is cultivated in the same regions. But that is not all, for the great family of Leguminosae, whose numerous representatives encumber this continent, likewise furnishes the negro natives a food that is nearly as indispensable to them as the gourou or the products of the baobab - another valuable tree and certainly the most widely distributed one in torrid Africa. This leguminous tree, which is as yet but little known in the civilized world, has been named scientifically Parkia biglobosa by Bentham. The negroes give it various names, according to the tribe; among the Ouloffs, it is the houlle; among the Mandigues, naytay; in Cazamance (Nalon language), it is nayray; in Bornou, rounuo; in Haoussa, doroa; in Hant-fleure (Senegal), nayraytou. On the old mysterious continent it plays the same role that the algarobas do in young America. However, it is quite a common rule to find in the order Leguminosae, and especially in the section Mimosae, plants whose pods are edible. Examples of this fact are numerous. As regards the Mediterranean region, it suffices to cite the classic carob tree (Ceratonia siliqua), which also is of African nationality, but which is wanting in the warm region of this continent.

Throughout the tropical region of Africa, the aborigines love to consume the saccharine pulp and the seed contained in the pod of the houlle. Prepared in different ways, according to tribe and latitude, these two products constitute a valuable aliment. The pulp is consumed either just as it is or as a fermented beverage. As for the seeds, they serve, raw or roasted, for the production of a tea-like infusion (whence the name "Soudan coffee"), or, after fermentation in water, for making a national condiment, which in certain places is called kinda, and which is mixed with boiled rice or prepared meats. This preparation has in most cases a pasty form or the consistency of cohesive flour; but in order to render its carriage easier in certain of the African centers where the trade in it is brisk, it is compressed into tablets similar to those of our chocolate. As these two products are very little known in Europe, it has seemed to us that it would be of interest to give a description and chemical analysis of them. We shall say but little of the plant, which has sufficiently occupied botanists.

Figs. 1 TO 6.   PODS OF THE HOULLE AND MICROSCOPIC
Figs. 1 TO 6. - PODS OF THE HOULLE AND MICROSCOPIC DETAILS.

The houlle (Parkia biglobosa) is a large tree from 35 to 50 feet in height, with a gray bark, many branches, and large, elegant leaves. The latter are compound, bipinnate (Fig. 7), and have fifty pairs of leaflets, which are linear and obtuse and of a grayish green. The inflorescence is very pleasing to the eye. The flowers, say the authors of the Florae Senegambiae Tentamen, form balls of a dazzling red, contracted at the base, and resembling the pompons of our grenadiers (Fig. 8). The support of this latter consists only of male flowers. The fruit that succeeds these flowers is supported by a club-shaped receptacle. It consists of a large pod, which at maturity is 13 inches in length by 10 in width (Fig. 1). This pod is chocolate brown, quite smooth or slightly tubercular, and is swollen at the points where the seeds are situated. The pods are straight or slightly curved. The aborigines of Rio Nunez use the pods for poisoning the fishes that abound in the watercourses. We do not know what the nature of the toxic principle is that is contained in these hard pods, but we well know the nature of the yellowish pulp and of the seeds that entirely fill the pods.

Fig. 7.   PARKIA BIGLOBOSA.
Fig. 7. - PARKIA BIGLOBOSA.

Although the pulp forms a continuous whole, each seed easily separates from the following and carries with it a part of the pulp that surrounds it and that constitutes an independent mass (Fig. 2). This pulpy substance, formed entirely of oval cells filled with aleurone, consists of two distinct layers. The first, an external one of a beautiful yellow, is from 10 to 15 times bulkier than the internal one, which likewise is of a beautiful yellow.

Fig. 8   FLOWERS OF PARKIA.
Fig. 8 - FLOWERS OF PARKIA.

It detaches itself easily from the seed, while the internal layer, which adheres firmly to the exterior of the seed, can be detached only by maceration in water. This fresh pulp has a sweet and agreeable although slightly insipid taste. Upon growing old and becoming dry, it takes on a still more agreeable taste, for it preserves its sweetness and gets a perfume like that of the violet.

As for the seed, which is of a brown color and provided with a hard, shining skin, that is 0.4 inch long, 0.3 inch wide, and 0.2 inch thick. It is oval in form, with quite a prominent beak at the hilum (Fig. 4). The margin is blunt and the two convex sides are provided in the center with a gibbosity limited by a line parallel with the margin, and this has given the plant its specific name of biglobosa. The mean weight of each seed is 4½ grains. The skin, though thick, is not very strong. It consists, anatomically, of four layers (Fig. 5) of a thick cuticle, c; of a zone of palissade cells, z p; of a zone of cells with thick tangential walls arranged in a single row; and of a zone tougher than the others, formed of numerous cells with thick walls, without definite form, and filled with a blackish red coloring matter, cs. This perisperm covers an exalbuminous embryo formed almost entirely of two thick, greenish yellow cotyledons having a strong taste of legumine.

When examined under the microscope, these cotyledons, the alimentary part of the seed, have the appearance represented in Fig. 6, where ep is the epidermic layer and cp constitutes the uniform parenchyma of the cotyledonary leaf. This parenchymatous mass consists of oval cells filled with fatty matter and granules of aleurone.

According to some chemical researches made by Professor Schlagdenhauffen, the pulp has the following composition per 100 parts:

Fatty matter2.407
Glucose33.92
Inverted sugar7.825
Coloring matter and free acids1.300
Albuminous matter5.240
Gummy matter19.109
Cellulose8.921
Lignose17.195
Salts4.080
- - -
Total100.000

The salient point of these analytical results is the enormous quantity of matter (nearly 60 per cent.) formed almost exclusively by sugar. It is not surprising, from this that this product constitutes a food both agreeable and useful.

An analysis of the entire seed, made by the same chemist, has given the following results:

Solid fatty matter21.145
Unreduced sugar6.183
Undetermined matters5.510
Gummy matters10.272
Albuminoid matters24.626
Cellulosic matters5.752
Lignose and losses20.978
Salts5.534
- - -
Total100.000

The presence in these seeds of a large quantity of fatty matters and sugar, and especially of albuminoid matters (very nutritive), largely justifies the use made of them as a food. The innate instinct of the savage peoples of Africa has thus anticipated the data of science. - La Nature.