The Elements of Botany Part 12

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 Pa.s.sion-flowers (Fig. 260) the crown consists of numerous threads on the base of each petal.

[Ill.u.s.tration: Fig. 261. Front view of a papilionaceous corolla. 262.

The parts of the same, displayed: _s_, Standard, or Vexillum; _w_, Wings, or Alae; _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 b.u.t.terfly-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 (_Alae_), 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 ill.u.s.tration is from a species of Locust, Robinia hispida.

265. =l.a.b.i.ate Corolla= (Fig. 256-258), which would more properly have been called _Bil.a.b.i.ate_, that is, two-lipped. This is a common form of gamopetalous corolla; and the calyx is often bil.a.b.i.ate 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 bil.a.b.i.ate, as in the Sage, this alternation gives three lobes or sepals to the upper and two to the lower lip. Two forms of the l.a.b.i.ate 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.

[Ill.u.s.tration: Fig. 263. Corolla of a purple Gerardia laid open, showing the four stamens; the cross shows where the fifth stamen would be, if present.]

[Ill.u.s.tration: Fig. 264. Corolla, laid open, and stamens of Pentstemon grandiflorus, with a sterile filament in the place of the fifth stamen, and representing it.]

[Ill.u.s.tration: Fig. 265. Corolla of Catalpa laid open, displaying two good stamens and three abortive ones or vestiges.]

266. There are all gradations between l.a.b.i.ate and regular corollas. In those of Gerardia, of some species of Pentstemon, and of Catalpa (Fig.

263-265), the l.a.b.i.ate character is slight, but is manifest on close inspection. In almost all such flowers the plan of five, which is obvious or ascertainable in the calyx and corolla, is obscured in the stamens by the abortion or suppression of one or three of their number.

[Ill.u.s.tration: Fig. 266. Two flower-heads of Chiccory.]

[Ill.u.s.tration: Fig. 267. One of them half cut away, better showing some of the flowers.]

267. =Ligulate Corolla.= The ligulate or _Strap-shaped_ corolla mainly belongs to the family of Compositae, in which numerous small flowers are gathered into a head, within an involucre that imitates a calyx. It is best exemplified in the Dandelion and in Chiccory (Fig. 266). Each one of these straps or _Ligules_, looking like so many petals, is the corolla of a distinct flower: the base is a short tube, which opens out into the ligule: the five minute teeth at the end indicate the number of const.i.tuent petals. So this is a kind of gamopetalous corolla, which is open along one side nearly to the base, and outspread. The nature of such a corolla (and of the stamens also, to be explained in the next section) is ill.u.s.trated by the flower of a Lobelia, Fig. 285.

[Ill.u.s.tration: Fig. 268. Head of flowers of a Coreopsis, divided lengthwise.]

268. In Asters, Daisies, Sunflower, Coreopsis (Fig. 268), and the like, only the marginal (or _Ray_) corollas are ligulate; the rest (those of the _Disk_) are regularly gamopetalous, tubular, and five-lobed at summit; but they are small and individually inconspicuous, only the _ray-flowers_ making a show. In fact, those of Coreopsis and of Sunflower are simply for show, these ray-flowers being not only sterile, but _neutral_, that is, having neither stamens nor pistil. But in Asters, Daisies, Golden-rods, and the like, these ray-flowers are pistillate and fertile, serving therefore for seed-bearing as well as for show. Let it not be supposed that the show is useless. See Section XIII.

[Ill.u.s.tration: Fig. 269. A slice of the preceding more enlarged, with one tubular perfect flower (_a_) left standing on the receptacle, with its bractlet or chaff (_b_), one ligulate and neutral ray-flower (_cc_) and part of another; _dd_, section of bracts or leaves of the involucre.]

269. =Adnation, or Consolidation=, is the union of the members of parts belonging to different circles of the flower (256). It is of course understood that in this (as likewise in coalescence) the parts are not formed and then conjoined, but are produced in union. They are born united, as the term _adnate_ implies. To ill.u.s.trate this kind of union, take the accompanying series of flowers (Fig. 270-274), shown in vertical section. In the first, Fig. 270, Flax-flower, there is no adnation; sepals, petals, and stamens, are _free_ as well as distinct, being separately borne on the receptacle, one circle within or above the next; only the five pistils have their ovaries coalescent. In Fig. 271, a Cherry-flower, the petals and stamens are borne on the throat of the calyx-tube; that is, the sepals are coalescent into a cup, and the petals and stamens are adnate to the inner face of this; in other words, the sepals, petals, and stamens are all consolidated up to a certain height. In Fig. 272, a Purslane-flower, the same parts are adnate to or consolidated with the ovary up to its middle. In Fig. 273, a Hawthorn-flower, the consolidation has extended over the whole ovary; and petals and stamens are adnate to the calyx still further. In Fig.

274, a Cranberry-blossom, it is the same except that all the parts are free at the same height; all seem to arise from the top of the ovary.

270. In botanical description, to express tersely such differences in the relation of these organs to the pistil, they are said to be

_Hypogynous_ (i. e. under the pistil) when they are all _free_, that is, not adnate to pistil nor connate with each other, as in Fig. 270.

[Ill.u.s.tration: Fig. 270. Flax-flower in section; the parts all free,--hypogynous.]

_Perigynous_ (around the pistil) when connate with each other, that is, when petals and stamens are _inserted_ or borne on the calyx, whether as in Cherry-flowers (Fig. 271) they are free from the pistil, or as in Purslane and Hawthorn (Fig. 272, 273) they are also adnate below to the ovary.

[Ill.u.s.tration: Fig. 271. Cherry-flower in section; petals and stamens adnate to tube of calyx,--perigynous.]

[Ill.u.s.tration: Fig. 272. Purslane-flower in section; calyx, petals, stamens, all adnate to lower half of ovary,--perigynous.]

_Epigynous_ (on the ovary) when so adnate that all these parts appear to arise from the very summit of the ovary, as in Fig. 274. The last two terms are not very definitely distinguished.

271. Another and a simpler form of expression is to describe parts of the flower as being

_Free_, when not united with or _inserted_ upon other parts.

_Distinct_, when parts of the same kind are not united. This term is the counterpart of coalescent, as free is the counterpart of adnate. Many writers use the term "free" indiscriminately for both; but it is better to distinguish them.

_Connate_ is a term common for either not free or not distinct, that is, for parts united congenitally, whether of same or of different kinds.

_Adnate_, as properly used, relates to the union of dissimilar parts.

272. In still another form of expression, the terms superior and inferior have been much used in the sense of above and below.

_Superior_ is said of the ovary of Flax-flower, Cherry, etc., because above the other parts; it is equivalent to "ovary free." Or it is said of the calyx, etc., when above the ovary, as in Fig. 273-275.

_Inferior_, when applied to the ovary, means the same as "calyx adnate;"

when applied to the floral envelopes, it means that they are free.

[Ill.u.s.tration: Fig. 273. Hawthorn-blossom in section; parts adnate to whole face of ovary, and with each other beyond; another grade of perigynous.]

[Ill.u.s.tration: Fig. 274. Cranberry-blossom in section; parts epigynous.]

273. =Position of Flower or of its Parts.= The terms superior and inferior, or upper and lower, are also used to indicate the relative position of the parts of a flower in reference to the axis of inflorescence. An axillary flower stands between the bract or leaf which subtends it and the axis or stem which bears this bract or leaf. This is represented in sectional diagrams (as in Fig. 275, 276) by a transverse line for the bract, and a small circle for the axis of inflorescence.

Now the side of the blossom which faces the bract is the

_Anterior_, or _Inferior_, or _Lower_ side; while the side next the axis is the

_Posterior_, or _Superior_, or _Upper_ side of the flower.

[Ill.u.s.tration: Fig. 275. Diagram of papilionaceous flower (Robinia, Fig.

261), with bract below; axis of inflorescence above.]

[Ill.u.s.tration: Fig. 276. Diagram of Violet-flower; showing the relation of parts to bract and axis.]

274. So, in the l.a.b.i.ate corolla (Fig. 256-258), the lip which is composed of three of the five petals is the _anterior_, or _inferior_, or _lower_ lip; the other is the _posterior_, or _superior_, or _upper_ lip.

275. In Violets (Fig. 238, 276), the odd sepal is posterior (next the axis); the odd petal is therefore anterior, or next the subtending leaf.

In the papilionaceous flower (Fig. 261, and diagram, Fig. 275), the odd sepal is anterior, and so two sepals are posterior; consequently, by the alternation, the odd petal (the standard) is posterior or upper, and the two petals forming the keel are anterior or lower.