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some of the masses of inflorescence loses its flowers; but at the same time acquires the property of twining round any object within its reach, and so of supporting the stem, which is too feeble to support itself. Such rachises form what is called a spurious cirrhus, or a cirrhus peduncularis, and are a striking exception to the general law that the cirrhus takes its rise from the petiole or midrib.
In the preceding account of the inflorescence I have treated the subject as heretofore, because it appears upon the whole more convenient to do so for the present, notwithstanding the recent ingenious observations of the Messrs. Bravais.
These botanists, together with Messrs. Schimper and Braun, and some others, led by their examination of the spiral arrangement of leaves into an investigation of the laws that regulate the arrangement of flowers, have proposed a new nomenclature and theory, of which the following is their own abstract (Ann. Sc., N. S., viii. 28.) :—
I. The inflorescence is a union of flowers grouped together in mutual relation. It may often be divided into other groups, essentially homogeneous with respect to each other, and which we call partial inflorescences; these inflorescences may sometimes be themselves subdivided; but something arbitrary may be sometimes found in the manner of their decomposition.
II. The flowers, or partial inflorescences which perform the part of them, have two distinct modes of evolution; the centripetal and the centrifugal.
III. The SPIKE is a centripetal inflorescence. (Plantago, Ribes, Leontodon, &c.)
IV. The COMPOUND SPIKE is centripetal, with two degrees of evolution; thus it is composed of partial inflorescences arranged centripetally, and these partial inflorescences are spikes. (Male flowers of Pinus.)
V. The CYME † is a centrifugal inflorescence. (He
Any centripetal group whatever, such as a partial umbel, raceme, spike, capitulum, provided the peduncles are destitute of lateral bracts. A centrifugal group, whose peduncles grow out of each other.
merocallis flava, Tradescantia, Strelitzia, Lamium, Cornus, Syringa.)
VI. The THYRSE* is an inflorescence at first centripetal, afterwards centrifugal. (Tamus, Delphinium, Laburnum.)
VII. The SARMENTIDIUM + is an inflorescence of which the first evolution is centrifugal: its partial inflorescences may belong to either of the four previous forms. (Cichorium Intybus, Vitis, Geranium molle, Asclepias.)
VIII. The cyme of Monocotyledons appears to be typically uninodal‡; it is helicoid §, or scorpioid ||, according as its peduncles are homodromal **, or antidromal. It may be binodal, trinodal ‡, multinodal ‡, in its first ramifications; but it has a tendency to become uninodal in its ultimate ramifications.
IX. The cyme of Dicotyledons is binodal, or multinodal ; the second is sometimes a simple variety of the first. In the binodal cyme one of the nodes is homodromal, the other antidromal. These nodes have usually an unequal tendency to develope; if the homodromal node causes the abortion of its antagonist, the cyme becomes by degeneration helicoid, and scorpioid in the opposite case. The multinodal cyme offers no fixed rule in the spirals of its nodes; it generally finishes by degenerating into little binodal few-flowered or one-flowered cymes. We therefore may consider the bi
* A group of cymes disposed centripetally, as the flowers are in the spike.
A group of cymes or spikes arranged centrifugally, as the flowers are in the cyme.
According as the peduncles bear 1, 2, or a variable number of nodes. Where the flowers are arranged in succession in a spiral around a pseudothallus (or axis of uniparous, that is one-peduncled, cymes, or sarmentidia, formed by a series of successive peduncles, fitted into each other in such a way that they seem to form but one and the same stalk, as in Hemerocallis fulva).
Where the flowers are arranged in two rows parallel to the axis of the pseudothallus, as in Canna indica.
** Where the direction of a spire is the same as on the central stem. ++ Where the direction of a spire is the reverse of that on the central
nodal cyme as the type of the cymes of dicotyledonous plants.
X. The helicoid cyme has a straight pseudothallus, not excentrical, often vertical.
XI. The scorpioid cyme has its pseudothallus rolled in a plane, excentrical, often horizontal volute, the two rows of flowers regarding the sky.
XII. A cyme may be either axillary or terminal. By decomposing the last into partial axillary cymes, we often arrive at the discovery upon the latter of the laws which the entire cyme did not offer.
XIII. The multinodal cyme, with axillary cymes, and subject to this decomposition, is sometimes rather difficult to distinguish from the thyrse. If the axillary cymes are oneflowered, there may be a difficulty in distinguishing them from the spike.
XIV. Cymes have another method of centrifugal evolution by the developement of accessory peduncles; these peduncles are of the same order as those which are born upon other nodes of the central peduncle, and are almost always antidromal.
XV. Sarmentidia follow in their organisation the same. laws as the cyme.
In this memoir of the Messrs. Bravais there is much which is ingenious; but their system is founded upon theoretical refinements, which require further consideration, and much simplification, before they can be advantageously applied to practical purposes.
6. Of the Calyx.
The calyx is the most exterior integument of the Flower, consisting of several verticillate leaves, either united by their margins or distinct, usually of a green colour, and of a ruder and less delicate texture than the corolla.
Authors have long disputed about the definition of a calyx, and the limits which really exist between it and the corolla: the above, which is copied from Link, seems to be the only
one that can be considered accurate. The fact is, that in many cases they pass so insensibly into each other, as in Calycanthus and Nymphæa, that no one can say where the calyx ends and the corolla begins, although it is evident that both are present. Linnæus, indeed, thought that it was possible to distingulsh them by their position with regard to the stamens, asserting that the divisions of the calyx are opposite those organs, and of the corolla alternate with them; but, if this distinction were admitted, the corolla of the Primrose would be an inner calyx, which is manifestly an absurdity. Jussieu defines a calyx by its being continuous with the peduncle, which the corolla never is; and this may seem in some cases a good distinction: but there are plenty of true calyxes, of all Papaveraceous and Cruciferous plants, for instance, in which the calyx is deciduous, and not more continuous with the peduncle than the corolla itself. The only just mode of distinguishing the calyx seems to me to be to consider it in all cases the most exterior verticillate series of the integuments of the flower within the bracts, whether it be half-coloured, deciduous, and of many pieces, as in Brassicaceae; membranous and wholly-coloured, as in Mirabilis; green and campanulate, or tubular, as in Laurus and Lythrum. Upon this principle, whenever there is only one series of floral integuments, that series is the calyx. A calyx, therefore, can exist without a corolla; but a corolla cannot exist without a calyx, either perfect or rudimentary.
The term Perianth is sometimes given as synonymous with calyx; but this is an error.
The word Perianth signifies the calyx and corolla combined, and is therefore strictly a collective term. It should only be employed to designate a calyx and corolla, the limits of which are undefined, so that they cannot be satisfactorily distinguished from each other, as in most Monocotyledonous plants, the Tulip and the Orchis for example. But since, even in such plants as these, there can be no reasonable doubt that the three outer floral leaves are the calyx, and the three inner the corolla (as is shown both by Tradescantia and its allies, in which the usual limits between calyx and corolla exist, and also by the usual origin of those parts in two distinct
whorls), the utility of the term Perianth is rendered extremely confined. It is often a mere evasion of the task of ascertaining the exact nature of the floral envelopes in doubtful cases. Some writers, among whom are Link and De Candolle, have substituted Perigonium for Perianthium: but the latter is in most common use, its application is well understood, and there is no good reason for its being changed. Ehrhart, with whom the name Perigonium originated, called it double when the calyx and corolla are evidently distinct, and single if they are not distinguishable: but this use of terms is obsolete.
The divisions of a calyx are called its sepals (sepala); a term first invented by Necker, and revived by De Candolle. Botanists of the school of Linnæus call them the leaflets or foliola. Link says the word sepalum is barbarous, and proposes to substitute phyllum. The sepals are generally longer than the corolla in æstivation, and during that period act as its protectors: during flowering they are mostly shorter.
The calyx, in ordinary cases, if deciduous, falls off from the peduncle by its base. In many cases the sepals drop off separately, as leaves fall from the stem ; but occasionally they cohere firmly into a sort of cap or lid, which is pushed off entire by the increase of the corolla and stamens: in these cases the calyx is said to be operculate, if it falls off without any lateral rupture of its cap, as in Eucalyptus; and calyptrate, if at the period of falling it bursts on one side, as in Eschscholtzia. In the former of these two cases, the cohesion between the sepals is complete and never destroyed; in the latter, two of the sepals separate, the cohesion between the remainder continuing complete.
The calyx of Compositæ is so very different in appearance from the calyx of other plants, that it is known by the particular name of pappus. It usually consists of hair-like processes proceeding from the apex of the ovary, in which case it is said to be pilose: if those hairs are themselves divided, it is plumose; if they are very unusually stiff, it is setose, in which case the setæ are often reduced in number to two, or even one; if the divisions of the pappus are broad and membranous,