Part 39

_Hermannia_, _Mahernia_, _Melochia_, etc., have flat petals with twisted æstivation; 5 undivided stamens, which usually are but slightly united at the base, and most frequently, without staminodes. _Thomasia_; _Helicteres_; _Sterculia_ (free follicles).--_Theobroma_, _Rulingia_, _Buettneria_, _Commersonia_, _Guazuma_, etc., have petals concave at the base, and terminating in a limb abruptly bent back, and at the boundary between them most frequently ligular outgrowths, as in certain genera of the Caryophyllaceæ; stamens 5–15–∞, anthers at the edge of a short tube and 5 linear staminodes (Fig. 441).--The Cocoa-tree (_Theobroma_), (Fig. 440) bears large, reddish-yellow, berry-like fruits, resembling short cucumbers, but ultimately becoming leathery to woody; in each of the 5 loculi are 2 (apparently only 1) rows of horizontal, oily seeds, as large as almonds. Cotyledons large, thick, and irregularly folded. Endosperm absent (Fig. 442).

49 genera, with about 750 species; almost entirely confined to the Tropics; none in Europe or in N. Asia.--The seeds of the Cocoa-tree (_T. cacao_, _bicolor_, _glaucum_, etc., natives of Trop. Am., especially north of the Equator) are used for chocolate and are also _officinal_ (“Cocoa-beans,” “Cocoa-butter,” “Oil of Theobroma”). Theobromine. _Cola acuminata_, Africa.

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.~

Of the other genera some have a bell-shaped, gamosepalous calyx, some have no corolla, the anthers of some open at the apex (_Aristotelia_, _Elæocarpus_, etc.), the majority have a capsule, some have berries, or drupes, some separate into fruitlets, etc.--_Corchorus_, _Triumfetta_ (nut, with hooked bristles), _Luehea_, _Apeiba_, etc. _Sparmannia_ is an African genus; 4-merous flowers; fruit a warted capsule; filaments numerous and sensitive to touch, the external ones are without anthers and moniliform above. The plant is covered with numerous soft and stellate hairs, and at the apex of the branches bears several cymose umbels.

POLLINATION in _Tilia_ is effected by insects, especially bees and Diptera, which swarm round the tree tops, allured by the numerous strongly-scented flowers and the easily accessible honey (formed in the hollow sepals). As the flowers are pendulous, the nectar is protected from ruin; and, in addition, the inflorescence is more or less concealed beneath the foliage-leaf. Self-pollination is impossible, on account of protandry.--About 470 species (nearly all trees and shrubs); especially in the Tropics, only a few being found in the temperate, none in the polar regions, or in high mountainous districts.--The inflorescence of the native species of _Tilia_ is medicinal. The wood is used for charcoal.--The majority are used for timber, and for the sake of the bast (“Bast,” “Jute,” the bast of _Corchorus textilis_, _Luehea_, and others).

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.

An _epicalyx_ is often found formed by _floral-leaves_ placed close beneath the calyx, in some 3, in others several. The median sepal is posterior in the species without epicalyx, often anterior in those which have an epicalyx.--The petals are _twisted either to the right or to the left_ in accordance with the spiral of the calyx; they are most frequently oblique, as in the other plants with twisted corollas, so that the portion covered in the æstivation is the most developed. The corolla drops off as a whole, united with the staminal tube.--Only the 5 petal-stamens are developed, but they are divided into a number of stamens, placed in 2 rows, and provided only with _half_-anthers (leaf-segments, see Fig. 446; the sepal-stamens are completely suppressed); these 5 staminal leaves are then united into a tube, frequently 5-dentate at the top, and bearing the anthers on its external side. The pollen-grains are specially large, spherical and spiny. There are from 3 to about 50 carpels united into one gynœceum and placed round the summit of the axis which most frequently projects between them. There is only 1 style, which is generally divided into as many stigma-bearing branches as there are carpels (Figs. 445, 448). The fruit is a schizocarp or capsule. Endosperm (Figs. 447 A, 451) scanty, often mucilaginous round the _embryo_, which is rich in oil.

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.

[_Bombax malabaricum_ is diplostemonous; the five sepal-stamens repeatedly branch, and the filaments bear unilocular anthers; the five petal-stamens bear bilocular anthers.]

=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.

_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.)