217. A Panicle, such as that of Oats and many Grasses, is a compound flower-cluster of a more or less open sort which branches with apparent irregularity, neither into corymbs nor racemes. Fig. 209 represents the simplest panicle. It is, as it were, a raceme of which some of the pedicels have branched so as to bear a few flowers on pedicels of their own, while others remain simple. A compound panicle is one that branches in this way again and again.
Fig. 210. Diagram of an opposite-leaved plant, with a single terminal flower. 211. Same, with a cyme of three flowers; a, the first flower, of the main axis; b b, those of branches. 212. Same, with flowers also of the third order, c c.
218. Determinate Inflorescence is that in which the flowers are from terminal buds. The simplest case is that of a solitary terminal flower, as in Fig. 210. This stops the growth of the stem; for its terminal bud, becoming a blossom, can no more lengthen in the manner of a leaf-bud. Any further growth must be from axillary buds developing into branches. If such branches are leafy shoots, at length terminated by single blossoms, the inflorescence still consists of solitary flowers at the summit of stem and branches. But if the flowering branches bear only bracts in place of ordinary leaves, the result is the kind of flower-cluster called
219. A Cyme. This is commonly a flat-topped or convex flower-cluster, like a corymb, only the blossoms are from terminal buds. Fig. 211 illustrates the simplest cyme in a plant with opposite leaves, namely, with three flowers. The middle flower, a, terminates the stem; the two others, b b, terminate branches, one from the axil of each of the uppermost leaves; and being later than the middle one, the flowering proceeds from the centre outwards, or is Centrifugal. This is the opposite of the indeterminate mode, or that where all the flower-buds are axillary. If flowering branches appear from the axils below, the lower ones are the later, so that the order of blossoming continues centrifugal or, which is the same thing, descending, as in Fig. 213, making a sort of reversed raceme or false raceme,—a kind of cluster which is to the true raceme just what the flat cyme is to the corymb.
220. Wherever there are bracts or leaves, buds may be produced from their axils and appear as flowers. Fig. 212 represents the case where the branches, b b, of Fig. 211, each with a pair of small leaves or bracts about their middle, have branched again, and produced the branchlets and flowers c c, on each side. It is the continued repetition of this which forms the full or compound cyme, such as that of the Laurestinus, Hobble-bush, Dogwood, and Hydrangea (Fig. 214).
Fig. 214. Compound cyme of Hydrangea arborescens, with neutral enlarged flowers round the circumference.
221. A Fascicle (meaning a bundle), like that of the Sweet William and Lychnis of the gardens, is only a cyme with the flowers much crowded.
222. A Glomerule is a cyme still more compacted, so as to imitate a head. It may be known from a true head by the flowers not expanding centripetally, that is, not from the circumference towards the centre.
223. The illustrations of determinate or cymose inflorescence have been taken from plants with opposite leaves, which give rise to the most regular cymes. But the Rose, Cinquefoil, Buttercup, etc., with alternate leaves, furnish also good examples of cymose inflorescence.
224. A Cymule (or diminutive cyme) is either a reduced small cyme of few flowers, or a branch of a compound cyme, i. e. a partial cyme.
225. Scorpioid or Helicoid Cymes, of various sorts, are forms of determinate inflorescence (often puzzling to the student) in which one half of the ramification fails to appear. So that they may be called incomplete cymes. The commoner forms may be understood by comparing a complete cyme, like that of Fig. 215 with Fig. 216, the diagram of a cyme of an opposite-leaved plant, having a series of terminal flowers and the axis continued by the development of a branch in the axil of only one of the leaves at each node. The dotted lines on the left indicate the place of the wanting branches, which if present would convert this scorpioid cyme into the complete one of Fig. 215. Fig. 217 is a diagram of similar inflorescence with alternate leaves. Both are kinds of false racemes (219). When the bracts are also wanting in such cases, as in many Borragineous plants, the true nature of the inflorescence is very much disguised.
Fig. 216. Diagram of a scorpioid cyme, with opposite leaves or bracts.
Fig. 217. Diagram of analogous scorpioid cyme, with alternate leaves or bracts.
226. These distinctions between determinate and indeterminate inflorescence, between corymbs and cymes, and between the true and the false raceme and spike, were not recognized by botanists much more than half a century ago, and even now are not always attended to in descriptions. It is still usual and convenient to describe rounded or flat-topped and open ramification as corymbose, even when essentially cymose; also to call the reversed or false racemes or spikes by these (strictly incorrect) names.
227. Mixed Inflorescence is that in which the two plans are mixed or combined in compound clusters. A mixed panicle is one in which, while the primary ramification is of the indeterminate order, the secondary or ultimate is wholly or partly of the determinate order. A contracted or elongated inflorescence of this sort is called a Thyrsus. Lilac and Horse-chestnut afford common examples of mixed inflorescence of this sort. When loose and open such flower-clusters are called by the general name of Panicles. The heads of Compositæ are centripetal; but the branches or peduncles which bear the heads are usually of centrifugal order.
228. These were simply indicated in Section II. 16. Some parts are necessary to seed-bearing; these are Essential Organs, namely, the Stamens and Pistils. Others serve for protection or for attraction, often for both. Such are the leaves of the Flower, or the Floral Envelopes.
229. The Floral Envelopes, taken together, are sometimes called the Perianth, also Perigone, in Latin form Perigonium. In a flower which possesses its full number of organs, the floral envelopes are of two kinds, namely, an outer circle, the Calyx, and an inner, the Corolla.
230. The Calyx is commonly a circle of green or greenish leaves, but not always. It may be the most brightly colored part of the blossom. Each calyx-leaf or piece is called a Sepal.
231. The Corolla is the inner circle of floral envelopes or flower-leaves, usually of delicate texture and colored, that is, of some other color than green. Each corolla-leaf is called a Petal.
232. There are flowers in abundance which consist wholly of floral envelopes. Such are the so-called full double flowers, of which the choicer roses and camellias of the cultivator are familiar examples. In them, under the gardener's care and selection, petals have taken the place of both stamens and pistils. These are monstrous or unnatural flowers, incapable of producing seed, and subservient only to human gratification. Their common name of double flowers is not a sensible one: except that it is fixed by custom, it were better to translate their Latin name, flores pleni, and call them full flowers, meaning full of leaves.
233. Moreover, certain plants regularly produce neutral flowers, consisting of floral envelopes only. In Fig. 214, some are seen around the margin of the cyme in Hydrangea. They are likewise familiar in the Hobble-bush and in Wild-Cranberry tree, Viburnum Oxycoccus; where they form an attractive setting to the cluster of small and comparatively inconspicuous perfect flowers which they adorn. In the Guelder Rose, or Snow-ball of ornamental cultivation, all or most of the blossoms of this same shrub are transformed into neutral flowers.
234. The Essential Organs are likewise of two kinds, placed one above or within the other; namely, first, the Stamens or fertilizing organs, and second, the Pistils, which are to be fertilized and bear the seeds.
Fig. 219. A stamen: a, filament; b, anther, discharging pollen.
Fig. 220. A pistil; with ovary, a, half cut away, to show the contained ovules; b, style; c, stigma.
235. A Stamen consists of two parts, namely, the Filament or stalk (Fig. 219 a), and the Anther (b). The latter is the only essential part. It is a case, commonly with two lobes or cells, each opening lengthwise by a slit, at the proper time, and discharging a powder or dust-like substance, usually of a yellow color. This powder is the Pollen, or fertilizing matter, to produce which is the office of the stamen.
236. A Pistil (Fig. 220, 221) when complete, has three parts; Ovary, Style, and Stigma. The Ovary, at base, is the hollow portion, which contains one or more Ovules or rudimentary seeds. The Style is the tapering portion above: the Stigma is a portion of the style, usually its tip, with moist naked surface, upon which grains of pollen may lodge and adhere, and thence make a growth which extends down to the ovules. When there is no style then the stigma occupies the tip of the ovary.
Fig. 221. Model of a simple pistil, with ovary cut across and slightly opened ventrally, to show the ovules and their attachment.
237. The Torus or Receptacle is the end of the flower-stalk, or the portion of axis or stem out of which the several organs of the flower grow, upon which they are borne (Fig. 223).
Fig. 222. Flower of Sedum ternatum, a Stonecrop.
Fig. 223. Parts of same, two of each kind, separated and displayed; the torus or receptacle in the centre; a, a sepal; b, a petal; c, a stamen; d, a pistil.
238. The parts of the flower are thus disposed on the receptacle or axis essentially as are leaves upon a very short stem; first the sepals, or outer floral leaves; then the petals or inner floral leaves; then the stamens; lastly, at summit or centre, the pistils, when there are two or more of them, or the single pistil, when only one. Fig. 223 shows the organs displayed, two of each kind, of such a simple and symmetrical flower as that of a Sedum or Stonecrop, Fig. 222.
239. All flowers are formed upon one general plan, but with almost infinite variations, and many disguises. This common plan is best understood by taking for a type, or standard for comparison, some perfect, complete, regular, and symmetrical blossom, and one as simple as such a blossom could well be. Flowers are said to be
Perfect (hermaphrodite), when provided with both kinds of essential organs, i. e. with both stamens and pistils.
Complete, when, besides, they have the two sets of floral envelopes, namely, calyx and corolla. Such are completely furnished with all that belongs to a flower.
Regular, when all the parts of each set are alike in shape and size.
Symmetrical, when there is an equal number of parts in each set or circle of organs.
240. Flax-flowers were taken for a pattern in Section II. 16. But in them the five pistils have their ovaries as it were consolidated into one body. Sedum, Fig. 222, has the pistils and all the other parts free from such combination. The flower is perfect, complete, regular, and symmetrical, but is not quite as simple as it might be; for there are twice as many stamens as there are of the other organs. Crassula, a relative of Sedum, cultivated in the conservatories for winter blossoming (Fig. 224) is simpler, being isostemonous, or with just as many stamens as petals or sepals, while Sedum is diplostemonous, having double that number: it has, indeed, two sets of stamens.
241. Numerical Plan. A certain number either runs through the flower or is discernible in some of its parts. This number is most commonly either five or three, not very rarely four, occasionally two. Thus the ground-plan of the flowers thus far used for illustration is five. That of Trillium (Fig. 226, 227) is three, as it likewise is as really, if not as plainly, in Tulips and Lilies, Crocus, Iris, and all that class of blossoms. In some Sedums all the flowers are in fours. In others the first flowers are on the plan of five, the rest mostly on the plan of four, that is, with four sepals, four petals, eight stamens (i. e. twice four), and four pistils. Whatever the ground number may be, it runs through the whole in symmetrical blossoms.
Fig. 226. Flower of a Trillium; its parts in threes.
Fig. 227. Diagram of flower of Trillium. In this, as in all such diagrams of cross-section of blossoms, the parts of the outer circle represent the calyx; the next, corolla; within, stamens (here in two circles of three each, and the cross-section is through the anthers); in the centre, section of three ovaries joined into a compound one of three cells.
242. Alternation of the successive Circles. In these flowers the parts of the successive circles alternate; and such is the rule. That is, the petals stand over the intervals between the sepals; the stamens, when of the same number, stand over the intervals between the petals; or when twice as many, as in the Trillium, the outer set alternates with the petals, and the inner set, alternating with the other, of course stands before the petals; and the pistils alternate with these. This is just as it should be on the theory that the circles of the blossom answer to whorls of leaves, which alternate in this way. While in such flowers the circles are to be regarded as whorls, in others they are rather to be regarded as condensed spirals of alternate leaves. But, however this may be, in the mind of a morphological botanist,
243. Flowers are altered Branches, and their parts, therefore, altered leaves. That is, certain buds, which might have grown and lengthened into a leafy branch, do, under other circumstances and to accomplish other purposes, develop into blossoms. In these the axis remains short, nearly as it is in the bud; the leaves therefore remain close together in sets or circles; the outer ones, those of the calyx, generally partake more or less of the character of foliage; the next set are more delicate, and form the corolla, while the rest, the stamens and pistils, appear under forms very different from those of ordinary leaves, and are concerned in the production of seed. This view gives to Botany an interest which one who merely notices the shape and counts the parts of blossoms, without understanding their plan, has no conception of.
244. That flowers answer to branches may be shown, first, from their position. As explained in the section on Inflorescence, flowers arise from the same places as branches, and from no other; flower-buds, like leaf-buds, appear either on the summit of a stem, that is, as a terminal bud, or in the axil of a leaf, as an axillary bud. And, as the plan of a symmetrical flower shows, the arrangement of the parts on their axis or receptacle is that of leaves upon the stem.
245. That the sepals and petals are of the nature of leaves is evident from their appearance; they are commonly called the leaves of the flower. The calyx is most generally green in color, and foliaceous (leaf-like) in texture. And though the corolla is rarely green, yet neither are proper leaves always green. In our wild Painted-cup, and in some scarlet Sages, common in gardens, the leaves just under the flowers are of the brightest red or scarlet, often much brighter-colored than the corolla itself. And sometimes (as in many Cactuses, and in Carolina Allspice) there is such a regular gradation from the last leaves of the plant (bracts or bractlets) into the leaves of the calyx, that it is impossible to say where the one ends and the other begins. If sepals are leaves, so also are petals; for there is no clearly fixed limit between them. Not only in the Carolina Allspice and Cactus (Fig. 229), but in the Water-Lily (Fig. 228) and in a variety of flowers with more than one row of petals, there is such a complete transition between calyx and corolla that no one can surely tell how many of the leaves belong to the one and how many to the other.
246. That stamens are of the same general nature as petals, and therefore a modification of leaves, is shown by the gradual transitions that occur between the one and the other in many blossoms; especially in cultivated flowers, such as Roses and Camellias, when they begin to double, that is, to change their stamens into petals. Some wild and natural flowers show the same interesting transitions. The Carolina Allspice and the White Water-Lily exhibit complete gradations not only between sepals and petals, but between petals and stamens. The sepals of our Water-Lily are green outside, but white and petal-like on the inside; the petals, in many rows, gradually grow narrower towards the centre of the flower; some of these are tipped with a trace of a yellow anther, but still are petals; the next are more contracted and stamen-like, but with a flat petal-like filament; and a further narrowing of this completes the genuine stamen.
247. Pistils and stamens now and then change into each other in some Willows; pistils often turn into petals in cultivated flowers; and in the Double Cherry they are occasionally replaced by small green leaves. Sometimes a whole blossom changes into a cluster of green leaves, as in the "green roses" occasionally noticed in gardens, and sometimes it degenerates into a leafy branch. So the botanist regards pistils also as answering to leaves; that is, to single leaves when simple and separate, to a whorl of leaves when conjoined.
248. The Deviations, as they may be called, from the assumed type or pattern of flower are most various and extensive. The differences between one species and another of the same genus are comparatively insignificant; those between different genera are more striking; those between different families and classes of plants more and more profound. They represent different adaptations to conditions or modes of life, some of which have obvious or probable utilities, although others are beyond particular explanation. The principal modifications may be conveniently classified. First those which in place of perfect (otherwise called hermaphrodite or bisexual) flowers, give origin to
249. Unisexual, or Separated, or Diclinous Flowers, imperfect flowers, as they have been called in contradistinction to perfect flowers; but that term is too ambiguous. In these some flowers want the stamens, while others want the pistils. Taking hermaphrodite flowers as the pattern, it is natural to say that the missing organs are suppressed. This expression is justified by the very numerous cases in which the missing parts are abortive, that is, are represented by rudiments or vestiges, which serve to exemplify the plan, although useless as to office. Unisexual flowers are
Monœcious (or Monoicous, i. e. of one household), when flowers of both sorts or sexes are produced by the same individual plant, as in the Ricinus or Castor-oil Plant, Fig. 230.
Diœcious (or Dioicous, i. e. of separate households), when the two kinds are borne on different plants; as in Willows, Poplars, Hemp, and Moonseed, Fig. 231, 232.
Polygamous, when the flowers are some of them perfect, and some staminate or pistillate only.
250. A blossom having stamens and no pistil is a Staminate or Male flower. Sometimes it is called a Sterile flower, not appropriately, for other flowers may equally be sterile. One having pistil but no stamens is a Pistillate or Female flower.
251. Incomplete Flowers are so named in contradistinction to complete: they want either one or both of the floral envelopes. Those of Fig. 230 are incomplete, having calyx but no corolla. So is the flower of Anemone (Fig. 233), although its calyx is colored like a corolla. The flowers of Saururus or Lizard's-tail, although perfect, have neither calyx nor corolla (Fig. 234). Incomplete flowers, accordingly, are
Naked or Achlamydeous, destitute of both floral envelopes, as in Fig. 234, or
Apetalous, when wanting only the corolla. The case of corolla present and calyx wholly wanting is extremely rare, although there are seeming instances. In fact, a single or simple perianth is taken to be a calyx, unless the absence or abortion of a calyx can be made evident.
Fig. 235. Flower of Mustard. 236. Its stamens and pistil separate and enlarged.
Fig. 237. Flower of a Violet. 238. Its calyx and corolla displayed: the five smaller parts are the sepals; the five intervening larger ones are the petals.
252. In contradistinction to regular and symmetrical, very many flowers are
Irregular, that is, with the members of some or all of the floral circles unequal or dissimilar, and
Unsymmetrical, that is, when the circles of the flower or some of them differ in the number of their members. (Symmetrical and unsymmetrical are used in a different sense in some recent books, but the older use should be adhered to). Want of numerical symmetry and irregularity commonly go together; and both are common. Indeed, few flowers are entirely symmetrical beyond calyx, corolla, and perhaps stamens; and probably no irregular blossoms are quite symmetrical.
253. Irregular and Unsymmetrical Flowers may therefore be illustrated together, beginning with cases which are comparatively free from other complications. The blossom of Mustard, and of all the very natural family which it represents (Fig. 235, 236), is regular but unsymmetrical in the stamens. There are four equal sepals, four equal petals; but six stamens, and only two members in the pistil, which for the present may be left out of view. The want of symmetry is in the stamens. These are in two circles, an outer and an inner. The outer circle consists of two stamens only; the inner has its proper number of four. The flower of Violet, which is on the plan of five, is symmetrical in calyx, corolla, and stamens, inasmuch as each of these circles consists of five members; but it is conspicuously irregular in the corolla, one of the petals being very different from the rest.
Fig. 239. Flower of a Larkspur. 240. Its calyx and corolla displayed; the five larger parts are the sepals; the four smaller, of two shapes, are the petals; the place of the fifth petal is vacant. 241. Diagram of the same; the place for the missing petal marked by a dotted line.
Fig. 242. Flower of a Monkshood. 243. Its parts displayed; five sepals, the upper forming the hood; the two lateral alike, broad and flat; the two lower small. The two pieces under the hood represent the corolla, reduced to two odd-shaped petals; in centre the numerous stamens and three pistils. 244. Diagram of the calyx and corolla; the three dotted lines in the place of missing petals.
254. The flowers of Larkspur, and of Monkshood or Aconite, which are nearly related, are both strikingly irregular in calyx and corolla, and considerably unsymmetrical. In Larkspur (Fig. 239-241) the irregular calyx consists of five sepals, one of which, larger than the rest, is prolonged behind into a large sac or spur; but the corolla is of only four petals (of two shapes),—the fifth, needed to complete the symmetry, being left out. And the Monkshood (Fig. 242-244) has five very dissimilar sepals, and a corolla of only two very small and curiously-shaped petals,—the three needed to make up the symmetry being left out. The stamens in both are out of symmetry with the ground-plan, being numerous. So are the pistils, which are usually diminished to three, sometimes to two or to one.
255. Flowers with Multiplication of Parts are very common. The stamens are indefinitely numerous in Larkspur and in Monkshood (Fig. 242, 243), while the pistils are fewer than the ground-plan suggests. Most Cactus-flowers have all the organs much increased in number (Fig. 229), and so of the Water-Lily. In Anemone (Fig. 233) the stamens and pistils are multiplied while the petals are left out. In Buttercups or Crowfoot, while the sepals and petals conform to the ground-plan of five, both stamens and pistils are indefinitely multiplied (Fig. 245).
256. Flowers modified by Union of Parts, so that these parts more or less lose the appearance of separate leaves or other organs growing out of the end of the stem or receptacle, are extremely common. There are two kinds of such union, namely:—
Coalescence of parts of the same circle by their contiguous margins; and
Adnation, or the union of adjacent circles or unlike parts.
257. Coalescence is not rare in leaves, as in the upper pairs of Honeysuckles, Fig. 163. It may all the more be expected in the crowded circles or whorls of flower-leaves. Datura or Stramonium (Fig. 246) shows this coalescence both in calyx and corolla, the five sepals and the five petals being thus united to near their tips, each into a tube or long and narrow cup. These unions make needful the following terms:—
Gamopetalous, said of a corolla the petals of which are thus coalescent into one body, whether only at base or higher. The union may extend to the very summit, as in Morning Glory and the like (Fig. 247), so that the number of petals in it may not be apparent. The old name for this was Monopetalous, but that means "one-petalled;" while gamopetalous means "petals united," and therefore is the proper term.
Polypetalous is the counterpart term, to denote a corolla of distinct, that is, separate petals. As it means "many petalled," it is not the best possible name, but it is the old one and in almost universal use.
Gamosepalous applies to the calyx when the sepals are in this way united.
Polysepalous, to the calyx when of separate sepals or calyx-leaves.
258. Degree of union or of separation in descriptive botany is expressed in the same way as is the lobing of leaves (139). See Fig. 249-253, and the explanations.
259. A corolla when gamopetalous commonly shows a distinction (well marked in Fig. 249-251) between a contracted tubular portion below, the Tube, and the spreading part above, the Border or Limb. The junction between tube and limb, or a more or less enlarged upper portion of the tube between the two, is the Throat. The same is true of the calyx.
260. Some names are given to particular forms of the gamopetalous corolla, applicable also to a gamosepalous calyx, such as
Wheel-shaped, or Rotate; when spreading out at once, without a tube or with a very short one, something in the shape of a wheel or of its diverging spokes, Fig. 252, 253.
Salver-shaped, or Salver-form; when a flat-spreading border is raised on a narrow tube, from which it diverges at right angles, like the salver represented in old pictures, with a slender handle beneath, Fig. 249-251, 255.
Fig. 248. Polypetalous corolla of Soapwort, of five petals with long claws or stalk-like bases.
Fig. 249. Flower of Standing Cypress (Gilia coronopifolia); gamopetalous: the tube answering to the long claws in 248, except that they are coalescent: the limb or border (the spreading part above) is five-parted, that is, the petals not there united except at very base.
Fig. 250. Flower of Cypress-vine (Ipomœa Quamoclit); like preceding, but limb five-lobed.
Fig. 251. Flower of Ipomœa coccinea; limb almost entire.
Fig. 252. Wheel-shaped or rotate and five-parted corolla of Bittersweet, Solanum Dulcamara. 253. Wheel-shaped and five-lobed corolla of Potato.
Bell-shaped, or Campanulate; where a short and broad tube widens upward, in the shape of a bell, as in Fig. 254.
Fig. 254. Flower of a Campanula or Harebell, with a campanulate or bell-shaped corolla; 255, of a Phlox, with salver-shaped corolla; 256, of Dead Nettle (Lamium), with labiate ringent (or gaping) corolla; 257, of Snapdragon, with labiate personate corolla; 258, of Toad-Flax, with a similar corolla spurred at the base.
Funnel-shaped, or Funnelform; gradually spreading at the summit of a tube which is narrow below, in the shape of a funnel or tunnel, as in the corolla of the common Morning Glory (Fig. 247) and of the Stramonium (Fig. 246).
Tubular; when prolonged into a tube, with little or no spreading at the border, as in the corolla of the Trumpet Honeysuckle, the calyx of Stramonium (Fig. 246), etc.
261. Although sepals and petals are usually all blade or lamina (123), like a sessile leaf, yet they may have a contracted and stalk-like base, answering to petiole. This is called its Claw, in Latin Unguis. Unguiculate petals are universal and strongly marked in the Pink tribe, as in Soapwort (Fig. 248).
262. Such petals, and various others, may have an outgrowth of the inner face into an appendage or fringe, as in Soapwort, and in Silene (Fig. 259), where it is at the junction of claw and blade. This is called a Crown, or Corona. In Passion-flowers (Fig. 260) the crown consists of numerous threads on the base of each petal.
Fig. 261. Front view of a papilionaceous corolla. 262. The parts of the same, displayed: s, Standard, or Vexillum; w, Wings, or Alæ; k, Keel, or Carina.
263. Irregular Flowers may be polypetalous, or nearly so, as in the papilionaceous corolla; but most of them are irregular through coalescence, which often much disguises the numerical symmetry also. As affecting the corolla the following forms have received particular names:
264. Papilionaceous Corolla, Fig. 261, 262. This is polypetalous, except that two of the petals cohere, usually but slightly. It belongs only to the Leguminous or Pulse family. The name means butterfly-like; but the likeness is hardly obvious. The names of the five petals of the papilionaceous corolla are curiously incongruous. They are,
The Standard or Banner (Vexillum), the large upper petal which is external in the bud and wrapped around the others.
The Wings (Alæ), the pair of side petals, of quite different shape from the standard.
The Keel (Carina), the two lower and usually smallest petals; these are lightly coalescent into a body which bears some likeness, not to the keel, but to the prow of a boat; and this encloses the stamens and pistil. A Pea-blossom is a typical example; the present illustration is from a species of Locust, Robinia hispida.
265. Labiate Corolla (Fig. 256-258), which would more properly have been called Bilabiate, that is, two-lipped. This is a common form of gamopetalous corolla; and the calyx is often bilabiate also. These flowers are all on the plan of five; and the irregularity in the corolla is owing to unequal union of the petals as well as to diversity of form. The two petals of the upper or posterior side of the flower unite with each other higher up than with the lateral petals (in Fig. 256, quite to the top), forming the Upper lip: the lateral and the lower similarly unite to form the Lower lip. The single notch which is generally found at the summit of the upper lip, and the two notches of the lower lip, or in other words the two lobes of the upper and the three of the lower lip, reveal the real composition. So also does the alternation of these five parts with those of the calyx outside. When the calyx is also bilabiate, as in the Sage, this alternation gives three lobes or sepals to the upper and two to the lower lip. Two forms of the labiate corolla have been designated, viz.:—
Ringent or Gaping, when the orifice is wide open, as in Fig. 256.
Personate or Masked, when a protuberance or intrusion of the base of the lower lip (called a Palate) projects over or closes the orifice, as in Snapdragon and Toad-Flax, Fig. 257, 258.