The fruit is a fleshy husk in one piece, formed of the dilated calyx; it generally retains the stigmas till it has nearly attained its full size, and when it becomes ripe it does not separate into valves, but bursts irregularly. The nut, on the contrary, is in two distinct valves, which may be easily separated from each other; and it is imperfectly divided into cells by four half dissepiments. The germ of the future plant is what children call the heart, and it is in the upper part of the kernel, with the root end uppermost, so that when a walnut is sown the sharp end should be placed downwards. The kernel is four-lobed, and deeply wrinkled; and when the young plant begins to grow, it divides into two cotyledons or seed-leaves, which drop off when the true leaves are fully developed. The kernel is covered with a thick skin, which is very astringent; and the nut is covered with a membranaceous network of strong veins, which are generally found in a withered state on opening the ripe husk, having left their impression deeply imprinted on the outside of the shell of the walnut. The leaves are impari-pinnate, consisting of four pairs of leaflets and a terminal single one; the lower pair of leaflets is much the smallest, and the other leaflets are frequently not opposite; and they are sometimes unequal at the base. The main petiole is dilated at the point where it joins the stem; and the leaves are placed alternately. The tree is large and widely spreading; and the timber is of a close grain, and takes a fine polish.
The Black Walnut (J. nigra) differs from the common kind, in the male
Fig. 78.—Leaf and fruit of the Black Walnut (Juglans nigra). flowers being on a smaller and more slender catkin, and furnished with a brown roundish bract at the back of the calyx. The female flowers are also in a sort of catkin, and four or five together. The fruit (see a in fig. 78) is round, and the husk very thick at first, but it gradually wastes away, when the seed is ripe, instead of opening. The leaves have seven or more pairs of leaflets, which are generally nearly opposite, and sometimes they are without the terminal single leaflet, as shown at b. The shell of the nut is very hard, and the dissepiments, which are also very hard, are generally perfect, and divide the kernel into four parts. The nuts should be sown as soon as possible after they are ripe, as they will not keep good above six months. The tree grows above seventy feet high, and the wood is very hard and black.
The Butter-nut (J. cathartica) resembles the Common Walnut in its male catkins, except that they are produced upon the old wood instead of being on the wood of the present year. The
Fig. 79.—Butter-nut(Juglans cathartica). female flowers grow four or five together in a short catkin, and they are distinguished by their stigmas, which are rose-coloured. The fruit (a in fig. 79) is pear-shaped, ending in a rather long point; and the kernel of the nut (b) resembles that of the Common Walnut, except in being more oily. The leaves (c) are like those of the Black Walnut, except that the leaflets are rather downy, and that there is a terminal one. The calyx of the female flower is also covered with a viscid down, which remains on the husk of the ripe fruit; and the shell of the nut is very hard and very much furrowed. The tree is of much smaller size than that of the Black Walnut, and it may be easily distinguished by the greyness of the bark of its young shoots; it also comes into leaf earlier, and the nuts are ripe about a fortnight sooner than the others. The wood is light, of a reddish colour, and rather a coarse grain.
THE GENUS CARYA.
The genus Carya (the Hickory) consists of ten or twelve species, which greatly resemble
