The genus Cydonia, the Quince, differs from Pyrus in having its seeds arranged in longitudinal rows, instead of being placed side by side. In the Chinese Quince there are thirty seeds in each row, arranged lengthways of the fruit. The ovary of this genus consists of five cells, each containing one row of seeds, the seeds being covered with a kind of mucilaginous pulp. The well-known plant, formerly called _Pyrus japonica_, has been removed to the genus Cydonia on account of its ovary and the disposition of its seeds, which are decidedly those of the Quince. It differs, however, from the common Quince in its seeds, which are arranged in two rows in each cell. [Illustration: FIG. 30.—FLOWER AND FRUIT OF THE HAWTHORN.] The common Hawthorn (_Cratægus Oxyacantha_) has generally only two styles (see _a_, _fig._ 30), but the number of styles varies in the many different species included in the genus from one to five. The corolla, calyx, and stamens are the same as in the other genera included in this tribe, but the petals (_b_) are rounder and rather more indented. The seeds vary from one to five, each being enclosed in a bony covering, or stone, the whole being surrounded by the fleshy part of the calyx, which forms the eatable part of the Haw. In some of the species the haws are so large as to appear like little apples; but they may be always easily distinguished by the ripe ovary, or case which incloses the seed, being bony; whereas in all the varieties of Pyrus, the outer part of the ovary is cartilaginous, like the core of the apple. The seeds of the Hawthorn are a long time before they come up, from the hardness of this bony covering, which does not open naturally when ripe. The species composing the genus Raphiolepis, the Indian Hawthorn, have been separated from Cratægus; chiefly on account of the covering which encloses the seeds being of a paper-like texture, instead of bony, and each cell containing two seeds. The limb of the calyx also falls off before the fruit is ripe, instead of remaining on to form what is called an eye, as it does in the common Hawthorn. The leaves of the plants belonging to this genus vary in the different species; but those of the common Hawthorn are wedge-shaped, and cut deeply into three or five lobes. The different species which compose the genus Cratægus were formerly considered to belong to the genus Mespilus. This genus, which is now almost confined to the common Medlar (_Mespilus germanica_), agrees with Cratægus in having each seed enclosed in a bony covering, but it differs in the limb of the calyx being in large leafy segments; and in the disk being very large and visible even when the fruit is ripe, from the tubular part of the calyx not closing over it.