This tribe is distinguished by the fruit, which is what botanists call a drupe, that is, a stone fruit. The principal genera included in this tribe are _Amygdalus_, the Almond; _Persica_, the Peach and Nectarine; _Armeniaca_, the Apricot; _Prunus_, the Plum; and _Cerasus_, the Cherry. All these genera contain more or less of prussic acid, which is found to exist principally in the leaves and kernels; and they all yield gum when wounded. The flowers of the common Almond (_Amygdalus communis_) appear, as is well known, before the leaves, bursting from large scaly buds, which when they open throw off the brown shining bracts in which they had been enwrapped. The calyx is somewhat campanulate, with the upper part cut into five teeth or lobes, and it is lined by the dilated disk. There are five petals, and about twenty stamens, both inserted in the lining of the calyx. The anthers are innate, and they differ from most of the other plants yet described in being only one-celled. The ovary is also only one-celled, and there are generally two ovules, though the plant rarely ripens more than one seed. The leaves are simple, and they have very small stipules. When the petals drop, the ovary appears covered with a thick tough downy pericarp, within which is the hard stone or nut, the kernel or almond of which is the seed. The Peach (_Persica vulgaris_) was formerly included in the same genus as the almond; and in fact there is but little botanical difference. The flowers are the same both in construction and appearance; and the leaves are simple like those of the almond, and, like them, they are conduplicate (that is, folded together at the midrib) when young. The only difference indeed is in the fruit; for, as everybody knows, the stone of the peach has not a dry tough covering, like that of the almond, but a soft and melting one full of juice, and the stone itself is of a harder consistence, and deeply furrowed, instead of being only slightly pitted. The fruit of the peach has thus a fleshy pericarp, the pulp or sarcocarp of which is eatable, and a furrowed nut or stone, inclosing the seed or kernel, which is wrapped up like that of the almond, in a thick loose skin. The Nectarine (_P. lævis_) only differs from the peach in the epicarp, or outer covering of the pulpy part, being smooth instead of downy. Of both fruits there are two kinds, one called free-stone, from their parting freely with the stone; and the other cling-stone, from the stone clinging to the fibres of the pulp.