Family 13. Columniferæ.

The chief characteristics of the orders belonging to this family are the ☿, regular, generally 5-merous, hypogynous flowers with 5-merous calyx, sepals united and valvate in the bud; petals 5, free (often twisted in the bud); stamens ∞ e.g.: 10, in two whorls, but one of these is more or less suppressed, often altogether wanting, or replaced by 5 staminodes, while the other (inner whorl) is generally divided more or less deeply into a large number of anther-bearing filaments. The filaments too (except Tiliaceæ) are united into a tube, which, especially in the Malvaceæ, forms a long column in the centre of the flower, surrounding the gynœceum (Figs. 445, 448); in this case, which is the most pronounced, the filaments are united into one bundle (monadelphous), in other instances, polyadelphous. The number of carpels varies greatly (2 to about 50), but they are nearly always united and form a syncarpous multilocular gynœceum.—The vegetative characters also closely agree, the leaves are always scattered and generally stipulate; all the green portions very often bear stellate hairs, and the bark in all the 3 orders is rich in tough bast. Mucilage is often present in cells or passages.—This family is connected with the Ternstrœmiaceæ, from which it is very hard to draw a sharp line of demarcation, and it is also allied to the Cistaceæ and to the Gruinales.

Order 1. Sterculiaceæ (including Buettneriaceæ). This is, no doubt, the least modified order, and one in which the stamens occur undivided. Obdiplostemonous. The 10 stamens in two whorls are most frequently united at the base into a short tube, and have 4-locular, extrorse anthers. The calyx-stamens are nearly always simple, tooth-like staminodes, situated on the edge of the tube, or are entirely suppressed. The same relation is found, for instance, in the Ampelidaceæ and Rhamnaceæ, namely 5 stamens in front of the 5 petals; not infrequently the 5 stamens are doubled (Fig. 441). Unisexual flowers are found in Sterculia, Cola, Heritiera. The corolla is often wanting, or developed in an unusual manner. Each loculus of the ovary (generally 5) always contains more than one ovule. Fruit a capsule. Androgynophore often present (Helicteres; Sterculia, etc.).

Order 2. Tiliaceæ. This differs from the other orders of the Columniferæ chiefly in the stamens being entirely free from each other, and also divided into many filaments, as far as the base, or at all events very far down, so that the flower appears to have numerous stamens or to be slightly polyadelphous (Fig. 443); in addition to this, it may be observed that the anthers are 4-locular and introrse. In Luehea the groups of stamens alternate with the petals. In a few genera (Corchorus, Triumfetta) 10 free and single stamens are found in 2 whorls; but, in the majority, groups of free stamens in separate bundles. The stamens are more or less united in Apeiba, Luehea. Style simple. Ovary 2-locular. The ovules are pendulous; raphe turned inwards. The calyx readily falls off; the æstivation of the entirely free petals is slightly imbricate (not twisted).

Tilia (Figs. 443, 444). Calyx and corolla 5-merous; the 5 staminal leaves (opposite the petals) divided as far as the base into a large number of stamens which are free or united into groups; gynœceum with 5 loculi in the ovary (opposite the sepals); there are 2 ovules in each loculus, though the ovary ripens into a 1-seeded nut, which is not detached from the axis of the inflorescence, but is carried away by the wind, whirling round and round, its large-winged bracteole serving as a parachute (Fig. 443).—Only trees, with alternate, obliquely heart-shaped and dentate leaves; stellate hairs, as in the other Columniferæ, are often present. The terminal bud of the branch always fails to develop, and the growth is then continued sympodially by the uppermost axillary buds. The INFLORESCENCE (Figs. 443, 444) is a 3–7-flowered dichasium (Fig. 444 t, d, e), which is developed in the axil of a foliage-leaf (Fig. 444). The first of its 2 bracteoles (a) is large, thin, leaf-like, and united with the inflorescence, the lower portion of which forms a broad wing, its so-called “bract”; the second bracteole (b), on the other hand, remains scale-like, and supports a winter foliage-bud covered with bud-scales which thus is situated at the base of the inflorescence, and is a bud of the 2nd order, in relation to the vegetative shoot. This bud is always found beneath the inflorescence on the branch placed horizontally, and the winged bracteole is always found above it, a relation which is connected with the fact that the 2 rows of shoots on the sides of a branch are antidromous with regard to each other.—The dichasium itself (Fig. 444) terminates with the flower (t); it has 3 floral-leaves (c, d, e), which soon fall off; c is barren: the other two bear flowers, or few-flowered dichasia, or unipared scorpioid cymes (indicated in the figure).—The foliage-leaves are folded in the bud upon the median line (1, 2, 3 in Fig. 444 are foliage-leaves with their 2 stipules), the inner half is broader than the outer, and after unfolding is turned away from the mother-axis (the position of the new inflorescences and vegetative buds is indicated in their axils on the figure).—The cotyledons on germination appear above the ground as large, lobed leaves.

Order 3. Malvaceæ (Mallows). The plants are easily recognised by the scattered, simple, palminerved, most frequently lobed, stipulate leaves, folded in the bud; the perfect, regular, hypogynous flowers, with gamosepalous, persistent, 5-merous calyx with valvate æstivation; the 5 petals twisted in the bud and united with one another at the base, and by the 5 apparently numerous stamens (Figs. 445, 448), with the filaments united into a tube, with reniform bilocular anthers opening by a crescentic slit (in 2 valves). Carpels 3–∞ united into one gynœceum; the embryo is curved and the cotyledons are folded (Figs. 447, 451); endosperm scanty, often mucilaginous.—Most of the plants belonging to this order are herbs, often closely studded with stellate hairs. The leaves are most frequently palmatifid or palmatisect.

The sub-orders may be arranged as follows:—

I. Carpels in one whorl.

A. The fruit a capsule, most frequently with loculicidal dehiscence, and many seeds in each loculus.

1. Gossypieæ. The staminal-column is naked at the apex, blunted, or 5-dentate.—Gossypium (the Cotton plant) has an epicalyx of 3 large ovate-cordate leaves, an almost entire, low and compressed calyx. Solitary flowers. Large, most frequently yellow, corollas. A 3–5-valved capsule with many spherical seeds. “Cotton” is the seed-hairs developed upon the entire surface of the seeds (Fig. 447), and consists of long, 1-cellular hairs, filled with air (and therefore white); these are thin-walled, with a large lumen, and during drying twist spirally, and come together more or less in the form of bands. They consist of cellulose, and have a cuticle.—Hibiscus has several, most frequently narrow, epicalyx-leaves, a distinct 5-toothed or 5-partite calyx.—Abutilon; Modiola.

B. Schizocarps, with 1-seeded fruitlets, most frequently nut-like and reniform (Figs. 449, 451).

3. Malveæ, Mallow Group. The carpels are arranged in one whorl (Fig. 449); the number of stylar-branches equals that of the carpels; fruitlets 1-seeded, reniform, indehiscent, but detaching themselves from one another and from the persistent central column (Figs. 450, 451).—Malva has an epicalyx of 3 free leaves. A flower with 2 suppressed bracteoles is situated in the axil of the foliage-leaves; one of these supports a homodromous foliage-shoot which forms a repetition of the main axis, the other an antidromous flower which continues the branching as a unipared scorpioid cyme.—Althæa, Rose Mallow, has an epicalyx of 6–9 leaves united at the base.—Lavatera, Sida, Anoda, Bastardia, etc., have no epicalyx.

II. Carpels arranged in a spherical head in five groups opposite to the petals.

Family 14. Tricoccæ.

The very large order Euphorbiaceæ and three smaller ones belong to this family. They have in common: unisexual, hypogynous, frequently regular flowers, the perianth most frequently single, rarely double, or entirely wanting; there is such a great variety in the structure and parts of the flower that one only can be cited as the rule: viz. the simple gynœceum composed of 3 carpels forming a 3-locular ovary, which is frequently more or less deeply grooved (hence the name, Tricoccæ); in the inner angles of the loculi are found 1 or 2 (never several) pendulous (except Empetraceæ), anatropous ovules, with upward and outwardly turned, frequently swollen, micropyle (Fig. 455). The seed most frequently has a large endosperm and a straight embryo (Figs. 455 B, 464).—The family approaches the nearest to the Gruinales and Columniferæ; it may perhaps be regarded as an offshoot from the Sterculiaceæ.

Order 1. Euphorbiaceæ. Flowers unisexual. In each of the loculi of the ovary, generally 3, there are 1 or 2 pendulous ovules with upward and outwardly turned micropyle. The placenta protrudes above the ovules (Figs. 454, 461 B). On the ripening of the capsule the 3 carpels separate septicidally, frequently with great violence, ejecting the seeds and leaving a central column. Endosperm copious.—For the rest, the flowers present all stages, from genera with calyx and corolla, to those which are the most reduced in Nature, namely the naked, 1-stamened flowers of Euphorbia.

The same variety which is found in the flower is also present in the vegetative parts. Some are herbs, as our Spurges, others are shrubs and trees; some African Euphorbia-species even resemble the habit of a Cactus. Leaf-like branches with rudimentary leaves are found in Phyllanthus (sub-genus Xylophylla) (Fig. 456). The leaves are scattered or opposite, often stipulate; they are nearly always simple. Large, highly-branched cells containing a great quantity of pungent latex are found in many, and watery juice in others. Glands and glandular hairs are general.—Only a few genera can be considered in this book.

As an example of the most perfect flowers (which partly reproduce the Geraniaceous type) may be mentioned, Croton, Manihot, and Jatropha; 5 sepals, 5 petals, sometimes gamopetalous, andrœcium diplostemonous, or many-stamened, often monodelphous.

Ricinus (Castor-oil) (Figs. 453–455); monœcious; the ♂-flowers, situated in the lower portion of the inflorescence, have 5 perianth-leaves and a large number of branched stamens; the ♀-flower has 3–5 perianth-leaves; 3 bifid styles. Leaves peltate, palmately lobed. The seeds (Fig. 455) contain an abundance of fatty oil and large aleurone grains.—Mercurialis (Mercury): the perianth is most frequently 3-merous; in the ♂-flowers 9–12 stamens; in the ♀-flowers most frequently a 2-locular gynœceum.—Phyllanthus: Pr3 + 3, A3, united in some and forming a column in the centre of the flower (Figs. 457, 458); Xylophylla is a section of this genus.— Hura crepitans (Sand-box tree) has a many-carpellate gynœceum, which separates with great violence when ripe.—A drupe is found in Hippomane mancinella (the Mancinil-tree, W. Ind.)—Alchornea (Coelebogyne) ilicifolia is well known on account of its “parthenogenesis”; only the ♀-plant has been introduced into Europe, but it nevertheless produces seeds capable of germination; these have generally several embryos.

Euphorbia (Spurge) has the most reduced flowers, which are borne in a very complicated inflorescence. Each ♂-flower (Fig. 460 B) is naked, and consists of one stamen only (terminal on the axis). In the closely allied genus Anthostema, a small perianth is situated at the place where, in Euphorbia, there is a joint in the “filament,” (Fig. 461 A). The ♀-flowers (Fig. 460) are naked, with a 3-locular ovary and 3 bifid styles. (Anthostema has a distinct perianth (Fig. 461 B); in a few Euphorbias traces of a perianth are present). In Euphorbia the ♂-and ♀-flowers are grouped into flower-like inflorescences termed “cyathia.” Each cyathium consists of a centrally placed ♀-flower which is first developed, surrounded by 5 groups of ♂-flowers (stamens) placed in a zig-zag, with a centrifugal order of development (Figs. 459, 460 B), that is, in unipared scorpioid cymes; these flowers are surrounded by an involucre of 5 leaves united into a bell-shaped structure (Fig. 459, 1–5) (resembling a calyx); on its edge are placed 4, generally crescent-like, yellow glands, one in each of the intervals, except one, between the lobes of the involucre (shaded in Fig. 459; see also Fig. 460 A). Scale-like thin structures (floral-leaves?) are situated between the ♂-flowers. The ♀-flower has a long stalk, and finally bends down on one side, namely to the place on the edge of the involucre where the gland is not developed. These cyathia are again arranged in an inflorescence which commences as a 3–5-rayed umbellate cyme (pleiochasium), the branches of which ramify dichasially and finally as scorpioid cymes.—Latex, with peculiar-shaped starch-grains, is found in laticiferous cells (especially in the Cactus-like, leafless species.)

Family 15. Terebinthinæ.

The diagram of the flower (Figs. 465–467) is the same as in the Gruinales, namely S, P, A2 and G in whorls of 5 (less frequently 3, 4, 6, 8), and the same modifications also occur with the suppression of the petal-stamens, etc. But a ring or sometimes cup-like glandular structure (disc) is found between the andrœcium and the gynœceum (Figs. 465, 466). The flowers similarly are regular, hypogynous, ☿ and polypetalous, though exceptions are found to all these characters: thus, for example, united sepals and petals frequently occur, and, in some orders, unisexual flowers by the suppression of one sex. In most cases the flowers are small, greenish-yellow, and arranged in paniculate inflorescences. The carpels (most frequently 5) are free in a few, but generally united into a multilocular gynœceum; rarely more than 1 or 2 ovules in each loculus. The gynœceum in the Anacardiaceæ is so reduced that it has only 1 fertile loculus with 1 ovule.—The ovules are epitropous, i.e. anatropous with outward-turned raphe (except the Anacardiaceæ).—The majority of the species are trees and shrubs with scattered, often compound (pinnate) leaves without stipules, and as in addition they frequently contain aromatic, especially turpentine-like substances, they assume a certain resemblance to the Walnut trees, and were formerly classed with them mainly on this account. In a series of genera the volatile, scented oils are found in special glands in the bark of the branches and in the leaves, in the latter case appearing as pellucid dots. This family includes several orders which are somewhat difficult to distinguish from each other.

Order 3. Rutaceæ. Leaves glandular with pellucid dots. The type is the same as that of the family. Flowers 4–5-merous. The ovary is most frequently 4–5-grooved. Disc well pronounced, often appearing as a “gynophore.” The majority are shrubs with alternate or opposite, compound, more rarely simple, leaves.

A. The ovary is deeply 2–5-cleft with basal styles which are more or less united; the carpels in some genera are entirely free (groups 1, 2). The fruit is capsular and most frequently dehisces like follicles along the ventral suture or septicidally, so that a horn-like internal layer (endocarp) separates elastically from the external layer.