In the earliest stages of growth, the young seeds, or _ovules_ as they are called, appear as little buds, arising from the inner wall of the ovary; and the part from which they arise is called the _placen´ta_ (_placenta_, a cake). In chickweed (Pl. I. fig. 41 _c_), the placenta forms a central column; and when the ovules are a little older, they are found to have separated somewhat from the placenta, but retaining a connexion by means of a little cord or stalk, termed the _funic´ulus_ (_funis_, a cord). The ovules may be readily found in the ovary or young pod of a wall-flower, the placentas forming four lines, running longitudinally down the interior of the pod. In this early condition the ovule consists of a mass of cellular tissue; and as new formations are soon added to it, it is termed in this state the _núcleus_. Around the nucleus are then formed two coats, an outer, called the prímine, and an inner, termed the secun´dine. These coats or membranes are open at one end, so as to leave a passage down to the apex of the nucleus; the opening is called the _forámen_. These structures are well seen in the ovule of the wall-flower (Pl. I. fig. 54), the foramen in the figure being indicated by a *; it will be noticed also that the funiculus runs down one side of the ovule, so as to terminate at the bottom or base of the nucleus. In ripe seeds, the spot at which the funiculus has been attached is mostly perceptible in the form of a scar. The slight prominence of the foramen can also often be distinguished, as in the seed of chickweed (Pl. I. fig. 51*); in the ripe seed the foramen is termed the _mícropyle_, and towards it the radicle of the embryo is always directed. One of the cells of the nucleus near its apex then enlarges, so as to form a sac, called the _embryo-sac_. This is excessively thin and transparent (Pl. I. figs. 45 _b_ & 47); and in it, also at the end next the foramen, one or more (in the chickweed one) smaller cells are formed from the cell-contents of the embryo-sac, which are called the _embryonal vesicles_ (Pl. I. fig. 45 _a_). Thus far developed, the embryo exists prior to the expansion of the flower and the discharge of the pollen. The embryo-sac is not figured in this early condition, the embryonal vesicle being then smaller than that in fig. 45 _b_, although occupying the same position. When the pollen has escaped from the anthers and fallen upon the stigma, the pollen-tubes growing down the intercellular passages of the style, enter the foramen of the ovule, and so reach the apex of the nucleus, at which the embryonal vesicle contained in the embryo-sac is situated. The end of the pollen-tube then adheres to the embryonal vesicle, and such interchange of cell-contents takes place between them as effects fertilization.