Part 44

=10.= DALBERGIEÆ. 25 genera; especially in Tropical America; the majority are trees, a few shrubs or lianes; the leaves are simple or imparipinnate. The fruit is _indehiscent_ in all; in some it is a winged, in others a wingless _nut_ (_Machærium_, _Dalbergia_, _Centrolobium_, etc.), in others, again, a drupe, _e.g._ in _Dipteryx_ (Tonquin-bean) and _Andira_. In some genera the embryo is straight.

POLLINATION. Especially effected by Bees. The nectar is secreted by a ring or disc-like portion round the base of the gynœceum or the inner surface of the receptacle. The flower is constructed with a peculiar mechanism to ensure cross-pollination by insects. The pollen is shed just before the flower opens, and is retained in a pouch formed by the keel. An insect visiting the flower uses the wings and keel for a landing-stage, and in attempting to reach the honey presses down the wings and the keel which are locked together near the standard; the stylar-brush by this means is forced through the apical opening of the keel and a little pollen is thus swept out and deposited upon the abdomen of the visiting insect as it presses against the apex of the keel; the insect thus carries away pollen and may effect cross-pollination. In the different flowers this arrangement is modified in various ways to promote pollination. 5000 species (319 genera); especially in the Tropics, where many are important forest trees.--The following plants are used FOR FOOD: _Pisum sativum_ (W. Asia?) and _arvense_ (Italy); _Phaseolus vulgaris_ (Kidney-bean, American; _Dolichos sinensis_ was known to the Greeks and Romans under the name “φασηλος,” “phaseolus”), _P. compressus_ (French-bean), etc.; _Faba_ _vulgaris_ (Field-bean, Horse-bean; from the Old World); _Ervum lens_ (Lentil, Eastern Mediterranean); in tropical countries the oil-containing seeds of _Arachis hypogæa_.--The following are FODDER plants: _Vicia sativa_, _Faba vulgaris_, _Onobrychis sativa_ (Sainfoin), _Medicago sativa_ (Lucerne), and _lupulina_ (Medick), species of _Trifolium_, _Hedysarum coronarium_. OFFICINAL: “Liquorice root,” from _Glycyrrhiza glabra_ (S. Europe); “Red Sandalwood,” from _Pterocarpus santalinus_ (Tropical E. Asia); Gum Tragacanth, from _Astragalus_-species (E. Mediterranean); Balsam of Peru, from _Toluifera pereiræ_, and Balsam of Tolu, from _Toluifera balsamum_. Calabar-beans, from _Physostigma venenosum_; Kino, from _Pterocarpus marsupium_; the pith of _Andira araroba_ is used under the name of “Chrysarobin.”--Of use TECHNICALLY: _Genista tinctoria_ (yellow dye) and _Indigofera-species_ (Indigo), the bast of _Crotalaria juncea_ (Sunn Hemp); the seeds of _Dipteryx_, which contain Coumarin, and are highly scented, and Balsam of _Myroxylon_. POISONOUS: the seeds of _Laburnum_ (_Cytisus laburnum_), various species of _Lathyrus_, and _Abrus precatorius_; the latter contain two poisonous proteids, paraglobulin and albumose, which resemble snake-poison in their effects. The following are ORNAMENTAL plants: _Phaseolus multiflorus_ (Scarlet runner, from America), _Robinia pseudacacia_, _Amorpha_, _Colutea_, _Coronilla_, _Indigofera dosua_, _Wistaria polystachya_, _Cytisus laburnum_ (Laburnum, S. Europe, Orient.) and other species.

Order 3. =Mimosaceæ.= The flowers are most frequently hypogynous and _regular_, the æstivation of the corolla is _valvate_ and, in the majority of instances, that of the calyx also. The flower is 4-merous, less frequently 5- or 3-merous.--The flowers are generally small, but are always borne in compact, round _capitula_ or spikes (Fig. 514); they are hypogynous or perigynous. The calyx is generally _gamosepalous_ and the corolla _gamopetalous_, the latter being frequently wanting. The stamens are equal or double the number of the petals (_Mimosa_, etc., in _M. pudica_, _e.g._ S4, P4, A4, G1) or (in _Acacia_, _Inga_, etc.) in a large, indefinite number, free or monadelphous, often united to the corolla (Fig. 514 _b_). The colour of the flower in most cases is due to the long and numerous stamens. The _fruit_ is various. The embryo is _straight_ as in the Cæsalpiniaceæ. _Entada_ and many species of _Mimosa_ have a flat, straight, or somewhat sickle-like pod, which resembles the siliqua of the Cruciferæ in that the sutures (in this instance, however, dorsal and ventral suture) persist as a frame, but the intermediate portion divides, as in the transversely divided siliqua, into as many nut-like portions as there are seeds. Some species have a pod of enormous dimensions. The seeds of _Entada gigalobium_ are often carried from the West Indies to the N. W. coasts of Europe by the Gulf Stream.--The fruit of _Acacia_ in some species is an ordinary pod, in others it is transversely divided, or remains an undivided fruit, a nut.--This order includes both trees and herbaceous plants, which are often thorny; the leaves are usually bipinnate (Fig. 514) and are sensitive, and also possess sleep-movements.--Many Australian Acacias have compound leaves only when young, but when old have _phyllodia_, _i.e._ leaf-like petioles without blades, placed vertically. A large number have thorny stipules, which in some (_Acacia sphærocephala_) attain an enormous size, and serve as a home for ants, which in return protect their host-plant against the attacks of other, leaf-cutting ants.

Other genera besides those mentioned are: _Adenanthera_, _Desmanthus_, _Parkia_, _Inga_ (with rather fleshy, indehiscent fruit), _Calliandra_, etc.

1350 species (30 genera); none natives of Europe, their home being the Tropics and sub-tropical regions, especially Australia and Africa.--Fossils in Tertiary.--Gums are found in many species of _Acacia_, especially the African (Gum arabic) and Australian, of which some are _officinal_. The bark, and also the fruits, contain a large amount of _tannic acid_ and are used as astringents and in tanning (“Bablah” is the fruits of several species of _Acacia_). Catechu is a valuable tanning material extracted from the wood of _Acacia catechu_ (E. Ind). The flowers of _Acacia farnesiana_ (Fig. 514) are used in the manufacture of perfumes. With us they are cultivated as ornamental plants, _e.g._ _A. lophantha_ and many others, in conservatories.

Family 22. =Passiflorinæ.=

The flowers are most frequently regular, 5-merous in the three most external whorls, eucyclic and perigynous or epigynous, less frequently hypogynous. A characteristic feature is that the ovary is _tricarpellary_, _unilocular_, and with 3 _parietal_ placentæ which sometimes meet in the central line (_Cucurbitaceæ_). The styles are generally free and _bifid_. To all these characteristics, however, there are exceptions. ~The Cucurbitaceæ are sometimes placed among the Sympetalæ, close to the Campanulinæ, but they are not allied to the Sympetalæ, from which they differ especially, for instance, in the structure of the ovule. The position of the Begoniaceæ in this family is also open to doubt.~

Order 1. =Passifloraceæ= (=Passion-flowers=). The majority are herbs which climb by means of tendrils (modified branches) and have scattered, stipulate leaves, often palminerved and lobed (Fig. 515). The flowers, which are often large and beautiful, are regular, ☿, with S5, P5, A5, G3; the calyx and corolla are _perigynous_, and immediately inside the corolla is the “corona,” consisting of numerous, tapering, filamentous bodies, or sometimes united in rings, most frequently petaloid and coloured; the stamens are raised on a long, round internode above the _cup-like receptacle_; immediately above these is the gynœceum with its 3 free styles and capitate stigmas; the ovary is unilocular with 3 parietal placentæ. Fruit most frequently a _berry_. The seeds have an aril.

210 species; especially in Tropical America. Several _Passiflora_-species are ornamental plants, and the fruits of some species are edible.

Order 2. =Papayaceæ.= The best known representative is the Papaw (_Carica papaya_), a Tropical American tree whose stem is usually unbranched, and bears at its summit several large, palmilobed leaves on long stalks. The stem and leaves have latex. The large, Melon-like berries are edible, and for this reason it is cultivated in the Tropics. Flowers unisexual, with slightly different structure in the ♂-and ♀-flowers, besides intermediate forms. The ♂-flower has a gamopetalous, the ♀-flower a polypetalous corolla.--The milky juice contains a substance with similar action to pepsine. 10 stamens. 5 carpels.

Order 3. =Turneraceæ.= 85 species; especially in America.

Order 4. =Samydaceæ.= 160 species; tropical.

Order 5. =Loasaceæ.= Herbaceous plants seldom shrubs, sometimes climbing, and nearly always studded with _stiff hairs_, in some instances stinging or hooked. The leaves are most frequently palmilobed and without stipules. The flowers are regular, ☿, polypetalous, entirely _epigynous_, with 4–5 sepals, petals and stamens, or more frequently (by splitting) many stamens, those which are placed before the sepals being generally barren and more or less petaloid; carpels most frequently 3, united into an inferior, unilocular ovary with 3 parietal placentæ, above which the receptacle is generally more or less prolonged. Fruit a capsule; in _Gronovia_ an ovary with 1 ovule and fruit a nut.

115 species; principally from S. Am. A number of annuals are often grown in our gardens: _Bartonia aurea_ (California); _Mentzelia_; _Cajophora_; _Gronovia_.

Order 6. =Datiscaceæ.= 4 species, especially in the Tropics.--_Datisca cannabina_ (Asia Minor) resembles the Hemp in external appearance. The flowers are diœcious, insignificant; ♂-flowers: a low, gamosepalous calyx, no corolla, and an indefinite number of stamens; ♀-flowers; _epigynous_; ovary unilocular with free, mostly bifid, styles, and generally 3 parietal placentæ. In most cases the ovary is not entirely closed at the top (as in _Reseda_).

Order 7. =Begoniaceæ.= This order principally comprises herbs or under-shrubs with succulent stems (having scattered vascular bundles in the pith); the leaves are arranged in two rows (a divergence of 1/2) and _are asymmetrical_, as a rule more or less obliquely cordate, or ovate with cordate base (Fig. 516); large, caducous stipules are present. Inflorescences dichasial, or unipared scorpioid cymes; the flowers are unisexual; the first ones (the oldest) are ♂-flowers, while ♀-flowers are found especially on the younger axes. The ♂-flowers have most frequently 2 + 2 coloured perianth-leaves, and many stamens collected into a head in the centre of the flower; the ♀-flowers are _epigynous_ with 5 coloured perianth-leaves (placed spirally with a divergence of 2/5) and a trilocular ovary, bearing 3 bifid styles and 3 wings (the wings usually of unequal size); in the inner angle of each loculus there is one large projecting placenta, or two plate-like placentæ (the bent back edges of the carpels) studded with ovules. Fruit a capsule, with many extremely small seeds.--_Begonia._

420 species; almost all from the Tropics (Am., Asia).--Many species, with varieties and hybrids, are ornamental plants in houses and conservatories, chiefly on account of the form, colour and markings of their leaves; but also for their very beautiful flowers. They reproduce easily by adventitious buds from leaves and portions of leaves placed on damp soil; some have bulbils. Like the Oxalideæ they contain an acid sap.

Order 8. =Cucurbitaceæ.= The flower is _epigynous_, and, as a rule, is also provided with a leaf-like, cup- or bell-shaped receptacle above the ovary, to which the perianth and stamens are attached; the flowers are regular, _unisexual_, with rudiments of the other sex, and 5-merous: sepals 5, narrow and pointed, with the median sepal posterior (Fig. 517), petals 5, stamens 5, and carpels 3 (rarely 4–5); the corolla is _gamopetalous_ in the majority, polypetalous in some; generally plicate-valvate in the bud. _The anthers in the ♂-flowers are extrorse, and monothecious, i.e. only one half of each of the anthers of the 5 stamens is developed_, the _pollen-sac_ having frequently a peculiar [tilde]-shaped curve (Fig. 518 _A_, _B_); the stamens are _either all united_ into a column (_e.g._ in _Cucurbita_), or they are _united in pairs_, so that only one remains free (Figs. 517 _A_; 518 _A_); in the latter case there appears to be one small stamen with a [tilde]-shaped, curved pollen-sac and two larger ones, each with two curved pollen-sacs placed as in Fig. 517 _A_. The original form appears to be _Fevillea_ with free petals and 5 free stamens. Sometimes the rudiment of a gynœceum is present. The carpels are united into an _ovary_ with 3 (4–5) placentæ formed by their united edges. These are thick, fleshy, and _bifid_, bearing a number of ovules on each side (Figs. 517 _B_; 518 _C_, _D_); in general the placentæ are so large that they not only meet in the centre, but also fill up the ovary as far as the wall of the pericarp. The whole interior of the fruit thus becomes a juicy mass in which three lines may be seen, meeting in the centre (the boundaries of the individual placentæ), and near the circumference 6 groups of seeds (Fig. 518 _D_). When the carpels are equal in number to the petals they alternate with them. The _style_ is short and thick, and generally divided into 3 (4–5) branches, with a horse-shoe shaped stigma on each branch (Fig. 518 _C_). The _fruit_ is most frequently a many-seeded _berry_; in some it attains a considerable size and has a firm external layer (_Cucurbita_, _Lagenaria_, etc.). _The embryo is straight_, has _no endosperm_, but contains a large quantity of _oil_. The exceptions to the above characters will be found under the genera.

Exclusively herbs, generally with stiff hairs and yellow flowers. Many species are annuals, others are perennial, having tuberous roots or hypocotyls. The leaves are scattered, long-stalked, in most cases more or less heart-shaped, palminerved, palmilobed, and exstipulate; in their axils are found both flowers (singly, or in an inflorescence) and a vegetative bud, and outside the axil, _on the anodic[37] side of the leaf, a simple or branched tendril_, by which the plant _climbs_ (exceptions: _e.g._ _Ecballium_).

The position of the flowers, branches and tendrils situated in and near the leaf-axils is as follows. In the leaf-axils, a flower is borne (as a branch of the first order), ♂ or ♀, according to the conditions of the various genera. This branch is not situated in the centre of the axil, but is removed slightly towards the anodic side of the leaf. Of its two bracteoles as a rule only the one lying on the anodic side is developed, namely as a tendril, which is displaced to a position outside the axil. The branch of the first order bears on its catodic side an inflorescence (in the axil of the suppressed bracteole), on the anodic side a vegetative bud which grows out into a branch like the main axis. The subtending leaf of this branch is thus the tendril; but when it has several arms the condition is complicated by the appearance of an accessory bud which unites with its subtending leaf, the tendril, its leaves also becoming tendrils (situated on an undeveloped internode); the many-branched tendril is thus a branch, and the tendril-arms are its leaves, except the main arm which is its subtending leaf. Other explanations of these difficult relations have been given.--The _germination_ is somewhat peculiar, owing to the fact that a heel-like prolongation is formed at the base of the hypocotyl to assist in separating the two halves of the testa from each other, and to facilitate the unfolding of the cotyledons.

_Cucurbita_ (Pumpkin, Marrow) has branched tendrils; the flowers are monœcious, and are borne singly; the corolla is bell-shaped, and divided almost as far as the middle. The stamens are all united into a tube; the compressed seeds have a thick, blunt edge.--_Cucumis_ has (generally) unbranched tendrils; the ♀-flowers are borne singly, whilst the ♂-flowers are borne in groups: the corolla is divided nearly as far as the base, and the stamens are united 2-2-1. The connective is elongated above the anthers. The seeds have a sharp edge.--_Citrullus_ (Fig. 518) has a corolla similar to _Cucumis_, but ☿-and ♂-flowers are borne singly; the stigma is only 3-lobed, the fruit most frequently spherical.--_Ecballium_ (Squirting Cucumber, only 1 species, E. _elaterium_) has no tendrils, and is therefore not a climber. The oblong fruit is pendulous from the apex of its stalk, and when ripe is distended with an acrid, watery fluid; on being touched the fruit is detached, and the seeds, together with the watery fluid, are violently ejected through the aperture formed at the base of the fruit. The ♂-flowers are borne in racemes near the solitary ♀-flowers (Fig. 517).--_Bryonia_ (White Bryony) has chiefly unbranched tendrils and small, greenish-yellow, usually diœcious flowers with rotate corolla, in many-flowered inflorescences; the small, spherical berry has no specially firm outer layer, and generally only few seeds. The tap-root and a few of the other roots are tuberous. _B. alba_ (berry black; monœcious) and _dioica_ (berry red; diœcious). ~Among other genera may be mentioned: _Lagenaria_ (Gourd); the fruit has a woody external layer which, after the removal of the pulpy integument, may be used as a gourd. _Luffa_ has a polypetalous corolla; the fruit is dry, and consists internally of a network of vascular bundles; it opens by an aperture at the summit. _Benincasa_; the fruit has a close, bluish coating of wax. _Trichosanthes_ (Snake Cucumber) has a thin, round, long and curved fruit. _Momordica_; the fleshy fruit opens and ejects the seeds. _Cyclanthera_ takes its name from the staminal column which is found in the centre of the ♂-flower, bearing a bilocular, ring-like anther which opens by a horizontal cleft. The fruit is unilocular by suppression, has 1 placenta, and when touched opens and ejects the seeds. _Sicyos_ and _Sechium_ have only unilocular ovaries with one pendulous ovule. _Sechium_ has, moreover, 5 free stamens, of which only one is halved, the other 4 having both halves of the anther. _Fevillea_ and _Thladiantha_ also have 5 free stamens. _Dimorphochlamys_ has dimorphic flowers.~

POLLINATION is effected by insects, chiefly bees or wasps, the nectar being secreted by the inner, yellow portion of the receptacle; in the ♂-flower access is gained to the nectar through the slits between the stamens, which arch over the nectary.--85 genera; about 637 species; especially in the Tropics. Only two are found in the whole of N. Europe, _Bryonia alba_ and _dioica_; in S. Europe, _Ecballium_ also. Most of the cultivated species have been obtained from Asia, such as the Cucumber, Melon, Colocynth, several _Luffa_-species (the “Gourds” mentioned in Scripture are _Cucumis chate_); from Africa, the Water-melon, _Cucurbita maxima_, and others; from S. Am., no doubt, the Pumpkin (_C. pepo_ and _melopepo_). USES. Many species are used in medicine or for domestic purposes. _Bitter_, _poisonous properties_ are found; the fruits of the two _officinal_ ones are purgative: _Citrullus colocynthis_ (Mediterranean, E. India, Ceylon) and _Ecballium elaterium_, as well as various tropical species, the roots of Bryonia, etc.--The following are cultivated AS ARTICLES OF FOOD: Pumpkin (_Cucurbita pepo_, etc.), Cucumber (_Cucumis sativus_), Melon (_Cucumis melo_), the Water-melon (_Citrullus vulgaris_), _Sechium edule_ (Chocho), certain species of _Luffa_ (the young fruit). The Bottle Gourd is cultivated in tropical countries for the sake of its hard pericarp, which is useful for bowls, bottles, etc. The fruits of _Luffa_ have a number of reticulately felted, tolerably firm vascular bundles, which render them serviceable in various ways (as a kind of “sponge”). The Cucurbits are of no use in the manufactures. Only a few are cultivated as ornamental plants, chiefly as curiosities.

Family 23. =Myrtifloræ.=

The leaves are most frequently _opposite_, _simple_, _entire_ (rarely dentate), and _exstipulate_. The flowers are _regular_ and _epigynous_ (perigynous in _Lythraceæ_ and a few others), ☿, polypetalous; the number of members in a whorl is generally 4 or 5 (S, P, A, or most frequently A 2, G), but sometimes it becomes (_e.g._ Myrtles and _Lythraceæ_) very large in the andrœcium by splitting, and in the gynœceum also is often different. (When suppression takes place it is principally in the corolla and petal-stamens.) In nearly all instances the calyx is _valvate_. Gyncœceum multicarpellary, multilocular, with only one _style_ (except _Haloragidaceæ_). In the majority the ovules are situated on an axile placenta in the multilocular ovary. _Endosperm is wanting_ in the majority.--~Less important exceptions: _Rhizophoraceæ_ and _Gunnera_ have stipules. _Haloragidaceæ_ have several styles and endosperm. _Rhizophora_ also has endosperm.~

Order 1. =Lythraceæ.= _Hermaphrodite_, _perigynous_ flowers which are _most frequently =6=-merous_, viz. S 6 (often with a _commissural_ “_epicalyx_,” Fig. 519 _c_), one segment posterior, P 6, A 6 + 6 or 6 + 0 and G =2–6=, forming a 2–6-locular ovary with many ovules in the loculi, style single, and capitate stigma. The _gynœceum is free_ at the base of the tubular, or bell-shaped, _thin_, strongly veined receptacle, which bears the other leaf-whorls on its edge and inner side. Fruit a capsule. No endosperm.--To this order belong both herbs, shrubs and trees. The branches are frequently square, the leaves always _undivided_, _entire_, and without stipules, or with several very small stipules, and often opposite. The calyx is valvate. The flower is regular (except _Cuphea_) and frequently large and beautiful. The stamens are generally incurved in the bud, and the petals irregularly folded.