« PreviousContinue »
The same may
it is said to be paleaceous : finally, it is sometimes reduced to a mere rim: in which case it is said either to be marginate, or to be none to have no existence. A calyx appears to be brought into this state by having no room to develope, in consequence of the pressure of the surrounding flowers. In such cases as this, where the calyx is altogether obsolete, the definition of that organ, as the most external of the floral envelopes, appears to be destroyed: but there can be no doubt that it is present in the form of a membrane adhering to the side of the ovary, although it is not visible to our eyes.
be said of such plants as those Acanthaceæ (Introduction to the Nat. Syst., p. 233.), in which, although the calyx is reduced to a mere ring, yet it does exist in the shape of that ring.
The Calyx being composed of leaves analogous to those of the stem, but reduced in size and altered in appearance, it will follow that it is subject to the same laws of developement as stem-leaves; and, as the latter, in all cases, originate imme: diately from the axis, below those that succeed them in the order of developement, so the calyx must always have an origin beneath those other organs which succeed it in the form of corolla, stamen, and pistil or ovary. Hence has arisen the axiom in botany, that whatever the apparent station of the calyx may be, it always derives its origin from below the ovary: nevertheless, it is often said to be superior.
If it is distinct from the ovary, as in Silene, it is said to be inferior or adherent (calyx inferus, or liberus); and the ovary is then called superior (ovarium superum, or liberum) (Plate V. fig. 3.); but if it is firmly attached to the sides of the ovary, so that it cannot be separated, as in Myriophyllum, it is then called superior, or free (calyx superus, or liberus), and the ovary inferior (ovarium inferum) (Plate V. fig. 7. 9.). From what has been said of pappus it will be obvious that it is a superior calyx.
The general opinion of botanists, in regard to the real nature of the superior calyx, is such as I have stated; and the accuracy of it in the majority of cases is indisputable: but it is by no means certain that, in some instances, what is called the tube of the calyx is not, as I have elsewhere stated
(Introduction to the Natural System, p. 26.), “ sometimes a peculiar extension or hollowing out of the apex of the pedicel, of which we see an example in Eschscholtzia, and of which Rosa and Calycanthus, and, perhaps, all supposed tubes without apparent veins, may also be instances.” And if this be so, the calyx may be superior in consequence of the cohesion of the ovary with the inside of an excavated pedicel, and not with the calyx itself.
When the sepals cohere by their contiguous edges into a kind of tube or cup, the calyx is said to be monophyllous ; an inaccurate term, which originated when the real nature of organs was unknown, and when a monophyllous calyx was thought to consist really of a single leaf, clipped into teeth at its margin. To avoid this inaccuracy, the word gamosepalous has been proposed. That the sepals are originally all distinct is not a matter of theory, but, as Schleiden rightly observes, of investigation to be established by actual evidence.
Various terms are employed to express the degree in which the sepals of a monophyllous calyx cohere: they will be explained in Glossology. When no cohesion whatever takes place between the leaves of a calyx, the term sepalous is employed with that Greek numeral prefixed, which is equivalent to the number of pieces; as, for example, if they are two, the calyx is disepalous; if three, trisepalous; if four, tetrasepalous, and so on.
Sometimes the calyx has certain expansions or dilatations, as in Scutellaria and Salsola. These are generally named appendages, and such a calyx is said to be appendiculate ; but Mænch has proposed a particular term for them, peraphyllum, which is; however, never used.
That envelope of the flower which forms a second whorl within the calyx, and between it and the stamens, is called the corolla. Its divisions always, without exception, alternate with those of the calyx, and are called petals. Like the sepals, they are either united by their margins, or distinct; but, unlike the calyx, they are rarely green, being for the most part either white, or of some colour, such as red, blue, or yellow, or of any of the hues produced by their intermixture. The corolla is generally also larger than the calyx.
Necker called the corolla perigynandra interior, and Linnæus occasionally gave it the name of aulæum, a term literally signifying the drapery of a room.
The alternation of the segments of the corolla with those of the calyx is a necessary consequence of their both being modifications of whorls of leaves, and therefore subject to the same laws of arrangement. If two whorls of leaves are examined, those of Galium, for example, they will always be found to be mutually so arranged, that if the internode which separates them were removed, they would exactly alternate with each other; and as there are no known exceptions to this law in real leaves, it is natural that it should not be departed from in any modifications of them.
When the petals of a corolla are all distinct, then the corolla is said to be polypetalous; but if they cohere at all by their contiguous margins, so as to form a tube, it then becomes what is called monopetalous ; an innacurate term of the same origin as that of monophyllous, in regard to calyx (see p. 165.), and for which that of gamopetalous has been sometimes substituted.
If the petals adhere to the bases of the stamens, so as to form a sort of spurious monopetalous corolla, as in Malva and Camellia, such a corolla has been occasionally called catapetalous ; but this term is never used, all such corollas being considered polypetalous.
When the petals are confluent into a monopetalous corolla, they constitute what is called a tube ; the orifice of which is the faux or throat. The principal forms of such a corolla are rotate (fig. 94.), hypocrateriform (fig. 92.), infundibuliform (fig. 95.), campanulate (fig. 96.), and labiate (fig. 93.). When the divisions of a monopetalous corolla do not, as in Campanula, spread regularly round their centre, but part take a direction upwards, and the remainder a direction downwards, as in Labiatæ, the upper form what is called the upper lip, and the lower, the lower lip, or labellum; the latter term is chiefly applied to the lower lip of Orchidaceous plants. If the upper lip is arched, as in Lamium album, it is termed the galea or helmet. When the two lips are separated from each other by a wide regular orifice, as in Lamium, the corolla is said to be labiate or ringent ; if the upper and lower sides of the orifice are pressed together, as in Antirrhinum, it is personate or masked, resembling the face of some grinning animal. In the latter the lower side of the orifice is elevated into two longitudinal ridges, divided by a depression corresponding to the sinus of the lip; this part of the orifice is called the palate. In ringent and personate corollas the orifice is sometimes named the rictus ; but this term is superfluous and little used.
A petal consists of the following parts: - the limb or lamina; and the unguis or claw. The claw is the narrow part at the base which takes the place of the foot-stalk of a leaf, of which it is a modification; the limb is the dilated part supported
upon the claw, and is a modification of the blade of a leaf. In many petals there is no claw, as in Rosa; in many it is very long, as in Dianthus. When the claw is present, the petal is said to be unguiculate. In some unnaturally deformed flowers the limb is absent, as in the garden variety of Rose, called R. Eillet, in which the petals consist wholly of claw.
According to the manner in which the petals of a polypetalous corolla are arranged, they have received different names, which are thus defined by Link: the rosaceous corolla (fig. 97.) has no claw, or it is very small; the liliaceous (fig. 71.) has its claws gradually dilating into a limb, and standing side by side; a caryophyllaceous has long, narrow, distant claws; the alsinaceous has short distant ones; the cruciate flower has four valvaceous sepals, four petals, and six stamens, of which two are shorter than the rest, and placed singly in front of the lateral sepals, and four longer, and standing in pairs opposite the two other sepals. If the corolla is very irregular, with one petal very large and helmet-shaped, or hooded, as in Aconitum, it is sometimes called cassideous ; if it resembles what is called labiate in monopetalous corollas, it is termed labiose. The corolla of the Pea, and most Leguminous plants, has received the fanciful name of papilionaceous or butterfly-shaped, (figs. 98, 99.); in this there are five petals, of which the upper is erect and more expanded than the rest, and is named the standard or vexillum; the two lateral are oblong, at right angles with the standard, and parallel with each other, and are called the wings or ale; and the two lower, shaped like the wings and parallel with them, cohere by their lower margin, and form the keel or carina. The wings were formerly called talare by Link, and the keel scaphium by the same author.
When the corolla is very small, or when it forms a part of a capitulum, it is called corollula : that of a floret is so called.