OF THE FRUCTIFICATION OF PLANTS.
Under the term fructification are com prehended, not only all the parts of the fruit, but also those of the flower, which last are indispensable for the perfecting of the former. All these organs are, there fore, essential to a vegetable, winch may be deficient in any of those that we have previously described, but can never be totally destitute of those, by which its species is propagated from generation to generation ; for propagation by cuttings, buds, or roots, is only the extension of an individual, the life and vigour of which gradually wears out, unless it be repro duced from seed. The fructification is, therefore, well defined by Linnaeus, as " a temporary part of vegetables, terminating the old individual and beginning the new." The parts which constitute these es sential organs are seven. 1. Calyx, fig. 35, the flower cup, or external covering of the flower. This also is of seven kinds. 1. Perianthium, or calyx, properly so call ed when it is contiguous to and makes a part of the flower, as the five green leaves which encompass a rose, including their urn-shaped base 2. Involucrum, which is remote from the flower, as in the umbel liferous tribe ; but if the idea of these plants, as above expressed, be just, the part in question ought rather to be con sidered as a bractea. 3. ..dmentum, a cat kin, is formed of numerous scales attached to one cylindrical receptacle, and falling off with it: in catkins which bear seed the scales are often enlarged, and har dened into a cone, as in the fir. 4. Spatial, a sheath, bursts longitudinally, and is more or less remote from the flower, as in the snow-drop, narcissus, and arum.
5. Gluma, a husk, is the peculiar chaffy calyx of grasses and their allies : to it belongs the arista or awn, which however is not constant in the same species of grass or corn : an elegant feathery awn is seen in the stipa pennata, feather-grass.
6. Perichatium, a scaly sheath, investing the fruit-stalk in some mosses, as hyp num. Volvo, the wrapper of the Fun gus tribe, is either of a membranous kind, sheltering their fructification, as in the common mushroom, or more coria ceous, investing the base of their stalk, as in many fungi.
2. Corolla, fig. 36, the delicate, gene rally coloured, leaves of a flower are al ways situated within the calyx, when both are present. This term comprehends both the petal, petaluin, and the nectary, nectorium. A flower consists of one pe tal, or of several, the former, denominat ed monopetalous, is either campanttlate, funnel-shaped, salver-shaped, wheel shaped, ringent like the mouth of an animal, or personate, closed by a palate. Its parts are the tube and the limb. A polypetalous corolla is either cruciform, as in a wall-flower, rosaceous, papiliona ceons, as in the pea-kind, or incomplete, when some parts found in analogous flowers are wanting. The parts of a po
lypetalous corolla are the claw and the border. The great point to be consider ed with respect to the corolla in general is, whether it be regular or irregular : in some flowers, however, it varies in the same species from one shape to the other, witness the genera antirrhinum and big nonia.
Neither the calyx nor corolla is indis pensably necessary to a flower: Both are wanting in hippuris, and one or other is deficient in many genera. Hence botanists are led into a perplexity, how, in some cases, to denominate the part which is present. When its green colour and thick texture agree with the generality of flower cups, we do not hesitate to esteem it such ; hut a calyx is often beautifully coloured, and there is some doubt whe ther the splendid leaves of tulips and lilies be not a true calyx ; at least they answer to the definition, that their parts are opposite to the stamens, whereas those of a corolla should be alternate with the latter. The Linnman hypothesis, how ever, though sanctioned by Jussieu, of the corolla proceeding from the inner bark, and the calyx from the outer, is en tirely subverted by recent and more cor rect observations on vegetable physiolo gy. The functions of these two parts are, perhaps, though similar, not exactly ana logous. Those of the calyx probably re semble what are performed by the leaves, and this part is presumed by Dr Smith even to secrete woody matter, for strengthening the fruit-stalk. The co rolla, indeed, seems destined to answer some exclusive purpose to the essential organs of impregnation with regard to air and light. It fades when they wither, and is altogether of temporary duration, Nectarizn, the nectary, fig. 37, is fre quently a part of, or an appendage to, the corolla ; sometimes the petal itself se cretes honey : sometimes a set of glands perform this function ; and in other cases there is a peculiar petal-like apparatus for preparing. or holding the nectarious juice. Linnxus has remarked that plants, whose nectary is distinct from the petals, are commonly poisonous, which in gene ral holds good with those of the more ela borate nectaries. A German writer, named Sprengel, has proved the corolla to be in many instances an attraction, as well as accommodation, for insects in their search after honey: lie remarks certain spots, called by him enacube indicantes, which he conceives are designed to di rect these little animals to their prey. The scent of flowers may perhaps con tribute to the same end. There can be no doubt that the use of the honey is to attract insects, to promote the impregna tion of the flower, and net, as some have thought, for the nourishment of the seeds or other organs, being frequently quite out of the reach of both.