Part 63

The order is the most advanced type of Columniferæ; it stands especially near to the Sterculiaceæ, but is separated from these and from the Tiliaceæ, among other characters, by its 2-locular (ultimately 1-chambered) anthers.

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.

=2.= BOMBACEÆ. The staminal tube is more or less deeply cleft into bundles, sometimes almost to the base; pollen smooth, style simple with capitate, lobed stigma. Almost all plants belonging to this group are trees, and in many instances have large barrel-shaped stems, that is, swollen in the centre, and sometimes covered with large warts. The wood is exceptionally light and soft. The flowers are often enormously large, and have beautiful petals; in some they unfold before the leaves. The capsule-wall is sometimes closely covered on its inner service with long, silky, woolly hairs, while the seeds themselves are generally without hairs. These hairs, however, on account of their brittle nature, cannot be used like those of the Cotton-plant. Digitate leaves are found in the Baobab-tree (Adansonia) from Africa, noted for its enormously thick, but short stem, and in the American Silk-cotton trees (Bombax, Eriodendron, Chorisia). Ochroma, Cheirostemon, Durio, and others also belong to this group. Durio is noted for its delicious fruits, which have a most unpleasant smell.

=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.~

=4.= URENEÆ, have always only 5 carpels arranged in 1 whorl, with 1 ovule in each loculus, and the fruit a schizocarp, generally with nut-like fruitlets provided with warts and hooks; but in some they dehisce by 2 valves (capsule). They differ principally from the other groups in having twice as many stylar-branches as carpels; the staminal tube is naked at the point, blunt or 5 toothed.--The genera Urena, Pavonia, Malachra, Malvaviscus (with berry-like fruits) belong to this group.

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

=5.= MALOPEÆ, differ from all the others in having a large number of fruitlets arranged irregularly in a round head, and separating considerably from each other even before maturity; there is, however, only 1 style, divided into a corresponding number of branches (this condition may be considered to have arisen from the branching [dédoublement] of 5 carpels). Malope has 3 large, heart-shaped (Kitaibelia 6–9) epicalyx-leaves, united at the base. Palava has no epicalyx.

POLLINATION. The majority have protandrous flowers, and are pollinated by insects. Between the basal portions of the 5 petals, there are 5 nectaries, protected from the rain by hairs, e.g. in Malva silvestris. When the flower first opens the numerous anthers occupy the centre of the flower, and the still undeveloped stigmas are concealed in the staminal tube; in the next stage the anthers are withered and empty, and the stigmas protrude and assume their places (Fig. 452). The large-flowered forms, it appears, are pollinated only by insects; but self-pollination takes place in small-flowered forms, as, for example, in Malva rotundifolia, in which the stylar-branches, twisting themselves, place the stigmas in between the undeveloped anthers.

DISTRIBUTION. 800 species (63 genera), most of which are natives of the Tropics, especially America. Althæa and some of the species of Malva are natives of the temperate regions of the Old World, the latter is also found in North America. Gossypium is tropical, no doubt especially Asiatic (G. herbaceum from India; G. arboreum from Upper Egypt). Cotton was introduced into Greece in the time of Herodotus, and was cultivated in America before the arrival of the Europeans.

USES. Pungent and poisonous properties are entirely wanting; mucilage, on the other hand, is found in abundance in all parts of the plant. Medicinal: the root of Althæa officinalis, leaves and flowers of Malva-species (M. silvestris vulgaris and borealis) and Gossypium.--The seeds contain a large quantity of fatty oil, which is in some cases extracted (Cotton-seeds and others). The seed-hairs of the Cotton plant are the most important product of the order. The cultivated forms of Cotton belong to several species: G. barbadense, herbaceum, religiosum, arboreum (Nankin), hirsutum, and others. According to other botanists, there are only 3 species. Bast is obtained from e.g. Hibiscus cannabinus (Gambo-hemp, Africa), Paritium tiliaceum and Sida retusa. The fruits of certain species of Hibiscus (e.g. H. esculentus, from Tropical Africa) are used in tropical countries as a vegetable before they are ripe.--The colouring matter in the flowers of Althæa rosea, var. nigra, is used for colouring wines, and hence is extensively cultivated in certain parts of Europe.--Ethereal oils and sweet-scented flowers are rare; but several species possess a peculiar musk-like odour (Malva moschata, Hibiscus abelmoschus, and others).--Many are cultivated as ornamental plants on account of the large flowers, e.g. Hollyhock (A. rosea, etc.), Lavatera trimestris, Malope grandiflora and trifida, Malva-species, Hibiscus rosa sinensis, syriaca; Sphæralcea, etc.

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.

FIG. 453.--♂-flower (magnified).

FIG. 454.--♀-flower in longitudinal section.

FIG. 455.--A seed entire; B in longitudinal section.]

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.

FIG. 456.--Leaf-like branch with flowers (nat. size).

FIG. 457.--♂-flower; and FIG. 458, ♀-flower (mag.).]

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.)

205 genera; more than 3,000 species; especially in the Tropics.--Many are used on account of the oil, and of the pungent (aperient, poisonous, anthelmintic, etc.) properties in the latex or the seeds. OFFICINAL: “Cascarilla-bark” of Croton eluteria; the fatty oil of the seeds of Croton tiglium (Trop. Asia); “Castor oil” from Ricinus communis (Africa, and cultivated in all warm climates throughout the world); the glandular hairs of Mallotus philippinensis (“Kamala”); this also yields a red dye. Gum “Euphorbium” is the hardened (resinous) latex of the Cactus-like Euphorbia resinifera (Morocco).--NUTRITIVE plants: Manihot utilissima and other species (Maniok, Am.). Their large, farinaceous roots form a very important article of food in the Tropics (Cassava-flour, Tapioca or Brazilian arrowroot). The fresh latex of the root in some species is a powerful poison; but the poisonous properties are diminished by roasting or cooking. Caoutchouc is obtained from Siphonia elastica (Trop. S. Am.). The vegetable tallow of the Chinese tallow-tree (Stillingia sebifera) is used in large quantities in soap factories. An indigo-like dye is obtained from Crozophora tinctoria, and is also found in Mercurialis perennis. Shellac is obtained from Aleurites laccifera. ORNAMENTAL plants: Acalypha, Croton, Dalechampia.--Hippomane is poisonous.

Order 2. =Buxaceæ.= This order differs from the Euphorbiaceæ in having the micropyle turned inwards; the ♂-flower has a 4-partite perianth and 4 stamens; the ♀-flower a 6-partite perianth and 3 carpels. Capsule with loculicidal dehiscence, the inner layer being detached elastically from the outer.--30 species. Shrubs without latex and with evergreen leaves.--Buxus sempervirens (Box) is an ornamental shrub (poisonous); it has a very hard and valuable wood which is used for wood-engraving and carving.