CHAPTER IV.

ORGANS Of reprodUCTION IN THE PHANERO

GAMIA.

THE Flower and its Appendages are called reproductive organs because they have for their especial office the reproduction of plants by the formation of seed.

The parts of a flower are only leaves in a modified condition; and hence a flower-bud is analogous to a leafbud, and the flower itself to a branch the internodes of which are but slightly developed; it is also subject to similar laws of arrangement and development.

SECTION 1.

INFLORESCENCE OR ANTHOTAXIS.

The term inflorescence or anthotaxis is applied generally to indicate the arrangement of flowers upon the floral axis. We have to examine-1st, the Leaf, from the axil of which the flower-bud or flower-buds arise; 2d, the Stalk, upon which the flower or flowers are situated; and 3d, the Kinds of Inflorescence.

I. The Bract.-In strict language the term bract should be only applied to the leaf from the axil of which a solitary flower or a floral axis arises; while all other leaves which are found upon that axis, between the bract and the flower properly so called, should be termed bractlets or bracteoles.

Bracts vary much in appearance, some of them being large, of a green color, and in other respects resembling

BRACTS-CUPULE.

the ordinary leaves of the plant upon which they are placed, as in the Pimpernel (Fig. 122, a, a); in which case they are called leafy bracts. In most cases bracts are smaller than the foliage leaves; and in many plants they are also different in color, outline, b texture, and other peculiarities. Thus the bracts forming the cupule of the Oak are hard and woody; in the Hop they are membranous; they may be colored or scaly; and other modifications also occur.

It frequently happens that some of the bracts do not develop axillary flower-buds, as in the common Pineapple (Fig. 123). Such bracts are called empty. When bracts are absent altogether, the plants are termed ebracteated; when present, the inflo

rescence is said
to be bracteated.

Bracts fol

a

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FIG. 122.-Flowering stalk of the Pimpernel (Anagallis arvensis). b, b. Solitary flowers arising from the axil of leafy bracts, a, a.

low the same law of arrangement as true leaves, being opposite, alternate, or whorled, in different plants. Bracts also vary in their duration, being deciduous or persistent in the same sense as leaves.

Sometimes the bracts of an involucre grow together at their base, and form ultimately a sort of cupshaped body surrounding the fruit, as the cup of the Acorn, and the

FIG. 123.—Pinapple fruit (So- husk of the Filbert or Hazel-nut; they then form what is called a cupule.

rosis), surmounted by a crown of empty bracts.

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SPATHE-PEDUNCLE.

When a bract is of large size and sheathing, and surrounds one, or a number of flowers, so as to completely inclose them when in a young state, it is called a spathe, The spathe is generally found surrounding the kind of inflorescence called a spadix, as in the Arum and Palm ; and it is also very common in other Monocotyledonous plants. Many botanists restrict the term spathe to the large enveloping bract of the spadix, and call the other bracts of a like character, which inclose only one or a few flowers, as frequently found in Monocotyledonous plants, spathaceous bracts.

II. The Peduncle or Flower-Stalk.-Under certain circumstances peduncles have received special names. Thus, when a peduncle is elongated, and gives off from its sides sessile flowers or branches bearing flowers, it is called the rachis or axis; but if, instead of being elongated in a longitudinal direction, it becomes shortened, more or less dilated, and commonly bearing numerous flowers, it is termed the receptacle.

When plants which have no aërial stem bear flowers, the peduncle necessarily arises at, or under the ground; it is then called a scape or radical peduncle.

The peduncle may become more or less compressed, or grooved in various ways, or excessively enlarged during the ripening of the fruit, or it may assume a spiral appearance, or become spiny, or transformed into a tendril; or may be hollowed out at its apex, so as to form a cupshaped body, to which the lower part of the calyx is attached, or other modifications may occur.

it

In some cases the peduncle or pedicel becomes flattened and assumes the form of a phyllode, when it is termed foliaceous or phylloid. Again, the peduncle, or several peduncles united, assume an irregular flattened appearance, and bear numerous flowers in a sort of crest at their extremities, as in the Cockscomb; and in the Cauliflower, where the united fleshy branches of the

KINDS OF INFLORESCENCE.

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peduncle form a rounded mass bearing on its upper part abortive flowers.

In some cases, the peduncle, instead of arising in the axil of a bract, may become extra-axillary by contracting adhesions to the axis or other parts. Thus, in the Limetree (Fig. 124), the peduncle adheres

to the midrib of the bract, b, for some distance, and then becomes free; the peduncle also becomes extra-axillary by forming adhesions to the stem or a branch in various ways.

The peduncle and pedicel may be caducous, deciduous, or persistent; and they are said to be excrescent, if they enlarge or continue to grow during the ripening of the fruit, as in the Cashew

nut.

III. Kinds of Inflorescence.The term inflorescence is used generally to indicate the arrangement of the

Lime-tree (Tilia europaa) attached to the bract, b.

flowers upon the floral axis or pedun- FIG. 124.-Peduncle of the cle, and as these are variously placed we have a number of different kinds of inflorescence, to each of which a particular name is applied. All the regular kinds may be arranged in two divisions, which are usually called Indefinite or Indeterminate, and Definite or Determinate Inflorescence. The former is also termed Botryoid or Botryose; and the latter Terminal and Cymose Inflorescence. In the former, the primary floral axis is terminated by a growing point, analogous to the terminal leaf-bud of a stem or a branch: hence such an axis has the power of either growing in an upward direction in the same manner as the terminal leaf-bud of a stem or branch has the power of elongating, and thus adding to its length, or of dilating more or less horizontally. There is consequently no necessary limit to the growth of

84

INDEFINITE INFLORESCENCE.

such an axis, and hence the name of Indeterminate or Indefinite which is applied to it. Such an axis, as it continues to grow upward, develops on its sides other flowerbuds, and these, like the buds of a stem or branch, are commonly situated in the axil of leaves which are here called bracts, as we have seen. All the flowers therefore of an Indefinite Inflorescence must be necessarily lateral or axillary, and hence this inflorescence is also termed axillary. The general characters of Indefinite, Indeterminate, or Axillary Inflorescence, depend therefore upon the indefinite growth of the primary axis; while the secondary, tertiary, and other axes which are developed from it are terminated by flower-buds. In the Definite or Determinate Inflorescence, on the contrary, the primary axis is terminated at an early period by the production of a flowerbud; such an axis has therefore a limit at once put to its growth in an upward direction, and hence the names of Definite, Determinate, or Terminal, applied to it. Each of these divisions also presents us with several modifications, which we now proceed to describe.

1. Indefinite, Indeterminate, or Axillary Inflorescence. The simplest kind of inflorescence in this class is that presented by such plants as the Pimpernel (Fig. 122), in which solitary flowers, b, b, are developed in the axils of what are commonly regarded as the ordinary leaves of the plant, a, a, although properly leafy bracts, the primary axis continuing to elongate in an upward direction and bearing other leaves and flowers. The flowers are then said to be solitary and axillary. When such flowers are arranged in whorls round the stem, they are said to be whorled.

When a number of flowers instead of a single one are developed upon an elongated, shortened, or dilated peduncle, placed at the extremity of a branch or in the axil of a bract, a number of kinds of inflorescence arise. All these depend upon the extent to which the floral axis