(_Parkia biglobosa._)
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 Leguminosæ,
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
Leguminosæ, and especially in the section Mimosæ, 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.
[Illustration: 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 _Floræ Senegambiæ 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.
[Illustration: 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.
[Illustration: 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 matter 2.407
Glucose 33.92
Inverted sugar 7.825
Coloring matter and free acids 1.300
Albuminous matter 5.240
Gummy matter 19.109
Cellulose 8.921
Lignose 17.195
Salts 4.080
-------
Total 100.000
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 matter 21.145
Unreduced sugar 6.183
Undetermined matters 5.510
Gummy " 10.272
Albuminoid " 24.626
Cellulosic " 5.752
Lignose and losses 20.978
Salts 5.534
-------
Total 100.000
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._
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