The fruit is the ovarium or pistillum arrived at maturity; but, although this is the sense in which the term is strictly applied, yet in practice it is extended to whatever is combined with the ovarium when ripe. Thus the pine-apple fruit consists of a mass of bracteæ, calyces, corollæ, and ovaria; that of the nut, the acorn, and many others, of the superior dry calyx and ovarium; that of the apple of succulent superior calyx, and corolla, and ovarium; and that of the strawberry-blite of a succulent inferior calyx and dry ovarium.

The fruit being the matured ovarium, it should exhibit upon some part of its surface the traces of a style or stigma; and this mark will, in many cases, enable the student to distinguish minute fruits from seeds. Many fruits were formerly called naked seeds, such as those of Umbelliferæ, Labiatæ, and Boragineæ, and the grain of corn; but now, that attention has been paid to the gradual developement of organs, such errors have been corrected. In cases where a trace of the style cannot be discovered, anatomy will generally show whether a minute body is a seed or fruit, by the presence, in the latter case, of two separable and obviously organically distinct coatings to the nucleus of the seed; but in other cases, when the pericarpium and the integuments of the seeds are combined in a single covering, and when no trace of style remains, as sometimes happens, nothing can be determined as to the exact nature of a given body without following it back in its growth to its young state. This, however,

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may be stated, that naked seeds, properly so called, are not known to exist in more than three or four orders in the whole vegetable kingdom; viz. in Coniferæ and Cycadeæ, where the ovula also are naked, and in Peliosanthes Teta and Leontice, in which the ovula, originally enclosed in an ovarium, rupture it at an early period after fertilisation, and subsequently continue naked until they become seeds.

Such being the case, it follows that all the laws of structure which exist in the ovarium are equally to be expected in the fruit; and this fact renders a repetition in this place of the general laws of formation unnecessary. Nevertheless, as, in the course of the advance of the ovarium to maturity, many changes often occur which contribute to conceal the real structure of the fruit, it is in all cases advisable, and in many absolutely necessary, to examine the ovarium, in order to be certain of the exact construction of the fruit itself. These changes are caused by the abortion, non-developement, obliteration, addition, or union of parts. Thus the three-celled six-ovuled ovarium of the oak and the hazel becomes, by the non-developement of two cells and five ovules, a fruit with one seed; the three-celled ovarium of the cocoa-nut is converted into a one-celled fruit by the obliteration of two cells and their ovula; and the two-celled ovarium of some Pedalineæ becomes many-celled by a division and elongation of the placenta.

In a very early state the ovarium of the Lychnis and of the primrose consists of five cells, each with a placenta having a number of ovula; by degrees the dissepiments are ruptured and obliterated by the rapid growth of the shell of the ovarium; and it finally becomes a fruit with only one cell, and a large fungous placenta in the middle. In Cathartocarpus fistula a one-celled ovarium changes into a fruit, having each of its many seeds lodged in a separate cell, in consequence of the formation of numerous horizontal membranes which intercept the seeds. A still more extraordinary confusion of parts takes place in the fruit of the pomegranate after the ovarium is fertilised; and many other cases might be mentioned.

Every fruit consists of two principal parts, the pericarpium and the seed, the latter being contained within the former.

When the ovarium is inferior, or coheres with the calyx, the latter and the pericarpium are usually so completely united as to be inseparable and undistinguishable: in such cases it is usual to speak of the pericarpium without reference to the calyx, as if no such union had taken place. Botanists call a fruit, the pericarpium of which adheres to the calyx, an inferior fruit (fructus inferus); and that which does not adhere to the calyx, a superior fruit (fructus superus). But M. Desvaux has coined other words to express these ideas: a superior fruit he calls autocarpien; an inferior fruit, heterocarpien ; terms wholly unnecessary and unworthy of adoption.

Every thing which in a ripe fruit is on the outside of the real integuments of the seed belongs to the pericarpium. It consists of three different parts, the epicarpium, the sarcocarpium, and the endocarpium; terms contrived by Richard, and very useful in practice.

The epicarpium is the external integument or skin; the endocarpium, called putamen by Gartner, the inner coat or shell; and the sarcocarpium, the intermediate flesh. Thus, in the peach, the separable skin is the epicarpium, the pulpy flesh the sarcocarpium, and the stone the endocarpium or putamen. In the apple and pear the epicarp is formed by the cuticle of the calyx, and the sarcocarpium is confluent with the remainder of the calyx in one fleshy body.

The pericarpium is extremely variable in size and texture, varying from the dimension of a single line in length to the magnitude of two feet in diameter; and from the texture of a delicate membrane to the coarse fabric of wood itself, through various cartilaginous, coriaceous, bony, spongy, succulent, or fibrous gradations.

The base of the pericarpium is the part where it unites with the peduncle; its apex is where the style was: hence the organic and apparent apices of the fruit are often very different, especially in such as have the style growing from their sides, as in Rosacea and Chrysobalaneæ, Labiatæ and Boragineæ.

When a fruit has arrived at maturity its pericarpium either continues perfectly closed, when it is indehiscent, as in the hazel-nut, or separates regularly round its axis, either wholly

or partially, into several pieces: the separation is called dehiscence, and such pieces valves; and the axis from which the valves separate in those cases where there is a distinct axis, is called the columella.

When the dehiscence takes place through the dissepiments it is said to be septicidal; when through the back of the cells it is called loculicidal; if along the inner edge of a simple fruit it is called sutural; if the dissepiments are separated from the valves the dehiscence is named septifragal.

In septicidal dehiscence the dissepiments divide into two plates and form the sides of v each valve, as in Rhododendron, Menziesia, &c. Formerly botanists said that in this sort of dehiscence the valves were alternate with the dissepiments, or that the valves had their margins turned inwards. This may

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be understood from fig. 167., which represents the relative position of parts in a transverse section of a fruit with septicidal dehiscence; v being the valves, d the dissepiments, and a the axis.

In loculicidal dehiscence the dissepiments form the middle of each valve, as in the lilac, or in the diagram 168., where the letters have the same value as above. In this it was formerly said that the dissepiments were opposite the valves.

In septifragal dehiscence the dissepiments adhere to the axis and separate from the valves, as in Convolvulus; or in the diagram 169., lettered as before.

In sutural dehiscence there are no dissepiments, the fruit being composed of only a one carpellum, as the pea.

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Besides these regular forms of valvular dehiscence, there is a mode which obtains in a very few plants, called circumscissile. This occurs by a transverse circular separation, as in Anagallis; in Jeffersonia it only takes place half round the fruit. Valvular dehiscence, which is by far the most common mode by which pericarpia open, must not be confounded with