[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 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.

[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 41/2 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.