449. Idea of the typical flower. In our idea of the typical flower, the perianth consists of two whorls of expanded floral leaves encircling and protecting the more delicate essential organs in their midst. The outer circle, calyx, is ordinarily green and far less conspicuous than the inner circle of highly colored leaves - the corolla.
450. Exception's. But to this, as to all other general rules, there are many exceptions. Strictly speaking, the calyx and corolla are in no way distinguishable except by position. The outer circle is the calyx, whatever be its form or color, and the inner, if there be more than one, is the corolla,
451. Rules. The sepals of the calyx and petals of the corolla are, according to rule, equal in number and severally disconnected save by the torus on which they stand.
452. Resemblances. The sepals more nearly resemble true leaves in texture and color; but the petals in form. Both have veins and re-tain more or less the same venation which characterizes the grand division to which the plant belongs (§ 258).
453. Parts. Both blade and petiole are distinguishable in the floral leaves, especially in the petals. The blade or expanded part is here called limb or lamina; the petiolar part, when narrowed into a stalk, is called the claw.
454. Nature of the sepals. The sepals are more generally sessile, like bud-scales, and appear to represent the leaf-stalk only, with margins dilated like a sheathing petiole. In confirmation of this view, we find in some flowers, as the paeony and rose, the lamina also developed, but smaller than the petiolar part.
455. Forms of petals. In form or outline there is a general resemblance between the limb and the leaf. It is ovate, oval, lanceolate, obcordate, orbicular, etc. In margin it is generally entire. Some peculiar forms, however, should be noticed, as the bilobate petal of the chickweed, the pinna-tifid petal of mitrewort, the inflected petal of the Umbeliferae, the fan-shaped petal of pink, the fringed (fimbriate) petal of campion (silene stellata), the hooded sepal of Napellus, the saccate petal of Calceolaria, Cypripedium.
456. Nectary. The limb is, moreover, often distorted into a true nectary, spurred, as already shown (§ 434), or otherwise deformed, as in Napellus, Coptis, etc.
Forms of petals. 294, Butter-cup, showing the scale at base.
295. Mignonette, fringed at top.
296, Silene stellata, fringed and unguiculate. 297, Flower of Onmorhiza longistylis, petals inflected. 29S, Flower of Mitella diphylla, petals pectinate-pinna-tifld. 299, Petal of Cerastium nutans, 2-cleft.
457. Union. We have seen that the floral organs are often in various ways united. Considering their crowded state in the flower, we rather wonder that they do not always coalesce in their growth.
458. The calyx with united sepals was called by the early botanists monosepalous; the corolla with united petals was called monopetalous (ľovoς, one - from the false idea that such an organ consisted of a single piece or leaf!). Opposed to these terms were polypetalous (πoλvς, many), petals distinct, and polysepalous, sepals distinct.
459. The monosepalous calyx, or monopetalous corolla, although thus compounded of several pieces, is usually described as a simple organ, wheel-shaped, cup-shaped, tubular, according to the degree of cohesion. The lower part of it, formed by the united claws, whether long or short, is the tube; the upper part, composed of the confluent laminae, is the border or limb; the opening of the tube above is the throat.
460. The border is either lobed, toothed, crenate, etc., by the distinct ends of the pieces composing it, as in the calyx of pink, the calyx and corolla of Primula, Phlox, and bellwort, or it may become by a complete lateral cohesion, entire, as in morning-glory. Here the compound nature of the organ is shown by the seams alone.
800, Flower of Saponaria (bouncing bet); petals and claws quite distinct. 801, Phlox; claw united, with lamina distinct. 302, Spigelia (pink-root), petals still further united. 803, Quamo-clit coccinea, petals united throughout
461. A terminal cohesion, where summit as well as sides are joined forming a cap rather than cup, rarely occurs, as in the calyx of the garden Escholtzia and the corolla of the grape.
462. The modes of adhesion are various and important, furnishing some of the most valuable distinctive characters. An organ is said to be adherent when it is conjoined with some dissimilar organ, as stamen with pistil. All the organs of our typical flower are described as free.
463. Hypogynous (vπώ, under, yuvή, pistil) is an adjective term in frequent use, denoting that the organs are inserted into the receptacle under or at the base of the free pistil or ovary. It is, therefore, not applicable to the pistil itself. Thus the outer organs of buttercups are hypogynous.
Section of flowers. 304, Jeffersonia diphylla, hypogynous. 305, Viola rotundifolia. 306 Phaseolns multitlorus (bean, organs spirally twisted). 307, Pyrus (Pear), perigynous; ovaries nearly inclosed. 308, Prunus (plum); ovary not inclosed.
464. Perigynous (περí, around) denotes that the organ is inserted on the calyx-tube around the free ovary. Thus in Phlox the stamens are inserted on the tube of the corolla. In cherry both stamens and petals are (apparently) inserted on the calyx-tube. The calyx can never be perigynous.
465. Epigynous (επě, upon) denotes that all the organs are apparently inserted upon the ovary, as seen in the apple, caraway, sunflower. The common phrases " calyx superior," " ovary inferior," have the same signification as calyx epigynous, all implying the apparent insertion of the organs upon or above the ovary.