Part 43

POLLINATION. _Prunus spinosa_ (Sloe, Blackthorn) is protogynous, but the stamens are developed before the stigma withers. Honey is secreted by the receptacle. _Cerasus padus_ (Bird-Cherry) agrees in some measure with _P. spinosa_. In the flowers of the Plum and Cherry the stamens and stigma are developed simultaneously and self pollination seems general; the stigma, however, overtops the inner stamens and thus promotes cross-pollination.--DISTRIBUTION. 114 species in the N. Temp, zone; few in the warmer regions; the majority from W. Asia. _C. vulgaris_, from the regions of the Caspian; _Prunus spinosa_, _insititia_ (Bullace), _domestica_ (Plum, from the Caucasus, Persia).--USES, principally as fruit-trees: Cherry, Plum, Apricot, etc.; “Almonds” are the seeds of _Amygdalus communis_ (W. Mediterranean), “bitter,” “sweet,” and “shell” almonds are from different varieties, the latter being remarkable for the thin, brittle stone. In the majority of species and in almost all parts of the plant (especially the bark, seed and leaves) is found the glycoside, _amygdalin_, which forms prussic acid. Many form _gum_, and the seeds have _fatty oils_ (“Almond oil”). OFFICINAL: the seeds and oil of _Amygdalus communis_, and the fruit of the Cherry; in other countries also the leaves of _C. laurocerasus_.--The stems of _Cerasus mahaleb_ are used for pipes. Ornamental Shrubs: _Amygdalus nana_, _Cerasus laurocerasus_.

Order 3. _Chrysobalanaceæ._ Tropical Amygdalaceæ with zygomorphic flower and gynobasic style. 200 species; especially Am. and Asia. _Chrysobalanus icaco_ (Cocoa-plum) is cultivated on account of its fruit (Am.)

Order 4. =Pomaceæ.= Trees and shrubs, most frequently with simple leaves and caducous stipules. The flowers (Fig. 505) have 5 sepals, 5 petals and generally 20 stamens (10 + 5 + 5, or 10 + 10 + 5). There are from 1–5 _carpels_, which unite entirely or to some extent with each other, and with the hollow, fleshy receptacle (the _flower_ becoming _epigynous_), (Figs. 505, 506, 507). The carpels are nearly always free on the ventral sutures, rarely free at the sides also. The whole outer portion of the fruit becomes fleshy, but the portions of the pericarp surrounding the loculi (endocarp) are most frequently formed of sclerenchymatous cells, and are more or less firm (the “core”). The nature of the fruit varies, according to the thickness and hardness of the endocarp, being either a “berry” or a “drupe” (see _A_ and _B_). When the endocarp is thin and parchment-like, the fruit has the characteristics of a berry, each of the 5 loculi generally present containing several seeds; but when this is hard the fruit resembles a drupe, only one seed is developed in each loculus, and the number of the loculi is reduced to one or two. There are nearly always 2 ovules in the loculi of the ovary, but in _Cydonia_ there are a large number in 2 rows. In the genera which have stones, only one seed is developed in each stone. The genera are distinguished mainly in accordance with the kind of fruit and the number of ovules and seeds.

=A.= SORBEÆ. THE ENDOCARP IS PARCHMENT-LIKE OR PAPERY (drupe, with thin stone or berry).

1. _Pyrus_ and _Cydonia_; carpels completely embedded in the cup-like receptacle, styles always free.--_Pyrus_: the fruit is glabrous, and has only a small calyx, withering or deciduous, and a 5-locular ovary with at most 2 ascending ovules in each loculus (Fig. 504 _D_). The large flowers are situated in few-flowered umbels or corymbs. ~_P. communis_ (Pear; free styles, Fig. 507; it has the well-known pear-shaped fruit; the core is reduced to several groups of sclerenchymatous cells embedded in the pulp, the leaf-stalk is as long as the blade).~--_Cydonia_ (Quince) has a hairy fruit with _many seeds in 2 rows_ in each loculus of the endocarp (Figs. 504 _C_, _F_; 506); the testa of these seeds is mucilaginous. _C. vulgaris_, large, terminal flowers on lateral branches, and large leaf-like, persistent sepals.

2. _Malus_ and _Amelanchier_ (_Aronia_); carpels free on the ventral edge; styles united. _Malus communis_ (Apple) the fruit is “umbilicate” at the base; no sclerenchymatous cells in the pulp; styles united at the base (Fig. 504 _D_); leaf-stalk shorter than the blade. _Sorbus_ (Mountain-ash) differs only in having a 2–3-locular fruit with extremely thin endocarp. Cymose inflorescences in umbellate cymes. ~_S. aucuparia_ has pinnate leaves, _S. aria_ (White-beam) and other species have simple leaves.--_Amelanchier_ (the Service-tree) has a false divisional wall springing from the dorsal suture, and more or less projecting into each of the loculi of the ovary; _Raphiolepis_ (Fig. 504 _E_) has racemes and a juicy berry; _Eriobotrya japonica_ (Loquat).~

=B.= CRATÆGEÆ. THE ENDOCARP IS HARD AND BONY (“drupes,” generally with several, sometimes, however, with only 1–2 stones, rarely one multilocular stone; only 1 seed in each of the loculi).--_Cratægus_ (Hawthorn, May). There are 1–5 stones in the spherical or ovoid fruit. The disc, found on the apex of the fruit, inside the small, withered calyx, is small (much less than the transverse section of the fruit). Shrubs with thorns (branches) and moderately large flowers borne in corymbs.--_Mespilus_ (Medlar) differs from the last-named only in having a _large disc_ at the apex of the fruit, inside the large, _leaf-like sepals_, _i.e._ almost equal to the greatest diameter of the fruit. The flowers are solitary and terminal.--_Cotoneaster_ is chiefly distinguished from the others by its syncarps, the 2–5 carpels (and stones) being free from one another, and only united to the receptacle by a larger or smaller portion of their dorsal surface (Figs. 504 _A_, _B_). Small shrubs with leathery leaves, generally covered with white, felted hairs on the lower surface, and with small flowers; the fruit is red or black.

Pear, Apple, Mountain Ash and Hawthorn have protogynous flowers which secrete honey, and are conspicuous to ensure insect pollination.--180 species; in the northern temperate regions.--Pear and Apple are especially cultivated as fruit trees in a number of varieties; the Paradise Apple (_Pyrus baccata_); especially in southern countries also the Quince (from N. Persia and the Caucasian districts), Medlar and _Amelanchier vulgaris_. _Malus pumila_ (Caucasus, Altai) and _M. dasyphylla_ (Orient, S. Eur.) are regarded as primitive forms of the Apple-tree; _M. sylvestris_, which grows wild in European forests, appears to have been less used. The early Lake-dwellers in Switzerland had the apple-tree both wild and cultivated.--The original form of the Pear is supposed to be _Pyrus achras_ (Central Asia).--Many of the species of _Cratægus_, some with double flowers, and _Pyrus (Chænomeles) japonica_, with brilliant red flowers, are cultivated as ornamental shrubs. OFFICINAL: Quince pips, on account of the mucilaginous testa.--The fruits contain free organic acids and sugar; prussic acid may be obtained from the seeds. The wood of the Pear-tree is used in manufactures.

Family 21. =Leguminosæ.=

The most characteristic feature is, that the _gynœceum is 1-locular_ and formed of _1 carpel, the ventral suture of which is turned posteriorly_. The fruit, in most instances, is a _pod_ (legume), which opens generally along both sutures, the two valves twisting more or less in opposite directions. ~In other instances it opens along one suture only, or as a pyxidium (Red Clover), or it is indehiscent, in which case it is more or less berry-like (_e.g._ the Tamarind, Carob-bean), or it is a drupe (_e.g._ the Tonquin-bean), or a 1–few-seeded nut (_e.g._ _Melilotus_), or a lomentum, which divides transversely into as many joints as there are seeds (_Ornithopus_, see Fig. 513).~

The inflorescences belong to the _centripetal_ type (_i.e._ indefinite); cymes do not occur. The flowers are _zygomorphic_, with vertical plane of symmetry, seldom regular; _5-merous_ with but a few exceptions, ☿, and slightly _perigynous_. The following diagram is the most general (Fig. 511): 5 sepals, with the _unpaired sepal median and anterior_, 5 petals, 5 + 5 stamens, all in alternating whorls, 1 carpel. The calyx is most frequently gamosepalous, the gynœceum is narrowed down at the base to a short stalk and, in the majority, is more or less bent. The seed is most frequently kidney-shaped, with a smooth, hard and shining testa, the hilum being very distinct. _Endosperm is wanting_, or is reduced to a thin layer, which is of service when the seed swells during germination. The vegetative parts have these features in common, namely, the _leaves are scattered, stipulate_, and almost always _compound_. Peculiar _sleep-movements_ and _sensitiveness_ are found in some, chiefly in the Mimosas. Many, probably all, Leguminosæ have _small tubercles on their roots_ which are produced by a kind of bacterium, and assist in the assimilation of free nitrogen. Spontaneous movements are exhibited by _Desmodium gyrans_ (Telegraph-plant).

This family is closely allied to the Rosifloræ, with which it agrees in the scattered leaves, the presence of stipules, the generally 5-merous and most frequently perigynous flowers with eucyclic stamens, and the absence of endosperm. _Amygdalaceæ_ and _Chrysobalanaceæ_, with solitary carpels, approach on one side to the Leguminosæ, among which genera with drupes are also found; _Mimosaceæ_, with their many stamens, form a connecting link on the other side. In this respect the Mimosa-genus _Affonsea_, and certain Cæsalpineæ and Swartzieæ, are of special interest in having more than one carpel (syncarp), a condition which is sometimes met with abnormally in other Leguminosæ, as well as in Amygdalaceæ. About 7,000 species of the Leguminosæ are known.

Order 1. =Cæsalpiniaceæ.= These are _leguminous plants with straight embryo and a flower which is not papilionaceous and has not the same æstivation_ (Figs. 508–510); but in reality there is not a single characteristic which absolutely distinguishes them from the Papilionaceæ.--The majority are arborescent; the leaves as a rule are pinnate or bipinnate. The flower is 5-merous, most frequently perigynous and slightly zygomorphic; the calyx is free or gamosepalous, the corolla polypetalous with _ascending imbricate æstivation_ (_i.e._ the two lowest petals envelop the lateral ones, and these again the posterior; Fig. 508); 10 _free stamens_; fruit various.

_Cassia_ (Figs. 508–510) is the largest genus (about 200 species); it has an almost hypogynous, zygomorphic flower with 5 free sepals and petals; of the 10 stamens the 3 posterior are generally barren, the others are of very unequal length and open at the apex by _pores_ (Fig. 509). In some (the _Senna_ group) the fruit is a flat, short, thin, dehiscing pod; in others (_Cathartocarpus_) it is round, long, woody or fleshy, indehiscent, and divided internally by more or less fleshy transverse walls into as many cells as there are seeds.--The following also have DEHISCENT FRUITS: _Bauhinia_ (often lianes, tropical climbers with tendrils [stem-structures] and anomalous stems), _Copaifera_, _Hæmatoxylon_ (whose pod does not dehisce along the suture, but laterally), _Cercis_ (simple leaves; the corolla resembles that of the Papilionaceæ, but the posterior petal is the smallest, and is enveloped by the 2 lateral ones, which are enveloped in their turn by the 2 anterior).--FRUIT INDEHISCENT: _Tamarindus indica_; the pod is almost round, often a little abstricted between the seeds; the wall is formed by a thin, brittle external layer, enclosing an acid pulp; well-developed septa are present, between the seeds; the most internal layer is parchment-like. Calyx 4-merous by the coalescence of 2 sepals. Only 3 fertile stamens.--_Ceratonia siliqua_ (Carob-bean, Locusts); the pod is long, compressed, with thick sutures, and has a wall, the central part of which is more or less leathery, fleshy and sweet; there are transverse septa between the seeds, as in the Tamarind. Embryo greenish in endosperm. The flower is without a corolla, 5 stamens.--_Pterogyne_ (winged fruit), etc.--KRAMERIEÆ with _Krameria_ is an anomalous group.

DISTRIBUTION. 80 genera, with 740 species; almost exclusively in the Tropics. The Carob-tree and _Cercis_ grow in the Mediterranean basin. The largest and most widely distributed genus is _Cassia_, which is found as trees, shrubs, and weeds in all tropical countries. The order has many important uses to mankind. MEDICINAL: the leaves and pods of _Cassia acutifolia_ and _angustifolia_ (officinal, Senna-leaves), the fruit-pulp of the _Cassia_-sub-genus, _Cathartocarpus_. Rhatany root from _Krameria triandra_ (Peru, officinal). _Balsam_ is extracted from a number of _Copaifera_-species (Balsam of Copaiba) from S. Am. (officinal), and from _Hymenæa_ (Copal balsam), _Trachylobium_ and others. _Edible fruits_ are obtained especially from the Carob-tree (from the East) and the Tamarind (officinal). The heart-wood of several species of _Cæsalpinia_, such as _C. brasiliensis_ (the Pernambuco-tree), _echinata_ (Red-tree), and _sappan_, yield _dyes_; _Hæmatoxylon_ (_H. campechianum_, Logwood), _Copaifera bracteata_ (Amarant-tree).--_Timber_ is obtained from many (_Melanoxylon_ and others). In Europe they are of little importance as ornamental plants, these being confined principally to the species of _Gleditschia_ (_G. triacantha_, from N. Am.) and _Cercis_ (the Judas-tree, _C. siliquastrum_, S. Eur.), which are cultivated in gardens; but in tropical gardens beautiful flowering species, _e.g._ of _Cassia_, _Poinciana_, _Brownea_, are found, and the most beautiful of all ornamental plants, the Indian _Amherstia nobilis_.

Order 2. =Papilionaceæ.= The flower (Figs. 511, 512) is _strongly zygomorphic_ and somewhat perigynous (Fig. 512 _B_; most frequently more on one side than the other). The calyx is _gamosepalous_ and persistent. The polypetalous corolla has _descending_ imbricate æstivation, the posterior, large leaf, the _standard_ (Figs. 511 _f_; 512 _B’_, _e_), _covering in the bud_ the two lateral ones, the _wings_ (Figs. 511 _v_; 512 _B’_, _a_), which again cover the two anterior; these are united in the form of a boat, the _keel_ (_k_ and _c_); the wings and the two petals of the keel are very unsymmetrical. That the keel is formed of two petals is seen by its position (in front of one sepal) and by the two often more or less free claws. The 10 (5 + 5) _stamens_ (monadelphous) _are either all united into one bundle, or into two bundles_ (diadelphous), the posterior one being free (Fig. 512 _C_). The ovules are _curved_ and _also the embryo_ (Fig. 512 _G_), especially the hypocotyl, so that the radicle assumes a position close to the edge of the thick, fleshy cotyledons. Endosperm wanting; the cotyledons are very rich in proteid reserve material. The forms of the fruit and exceptions are described under the genera.

_Geocarpic_ fruits, _i.e._ those which penetrate the soil during their development and ripen underground, are found in _e.g._ _Arachis hypogæa_ (see page 472), _Trifolium subterraneum_, _Vicia amphicarpæa_. _Germination_ takes place in various ways. In the majority the cotyledons are raised above the ground as green, leaf-like bodies; in the Vicieæ they remain thick and white, and are always enclosed in the testa, and are therefore never able to take part in the work of assimilation; in species of _Phaseolus_, on the other hand, they are raised well above the ground and become green, but remain however thick and fleshy.

=1, 2.= The two groups PODALYRIEÆ (the majority of the genera are Australian) and SOPHOREÆ (_Sophora_, _Edwardsia_, etc.), represent the oldest type, as they have 10 _free stamens_ and so form the transition to the Cæsalpiniaceæ. Nearly all are trees and shrubs.

=3.= ASTRAGALEÆ. Herbs or shrubs, less frequently trees, with _imparipinnate_ leaves (without tendrils). The flowers are generally borne in racemes or spikes. Stamens monadelphous or diadelphous.--_Astragalus_ (Milk-Vetch) has the legume incompletely divided longitudinally into 2 loculi by a septum formed by the incurved dorsal suture. Diadelphous.--_Glycyrrhiza_ (Liquorice); _Colutea_ (Bladder-Senna) from S. Europe; _Robinia_ (the false Acacia) with thorny stipules; _Indigofera_ (the Indigo plant); _Amorpha_ (which has only one petal, namely the standard, and the fruit a nut), _Caragana_, _Wistaria_ (a climbing shrub), _Galega_. _Carmichælia australis_, when old, produces flat branches with scale-like leaves.

=4.= VICIEÆ. _Climbing herbs_ with _paripinnate_ leaves, the midrib ending in a point or frequently in a _tendril_, which generally is branched, representing lateral veins without mesophyll; stamens diadelphous; the cotyledons remain underground on germination.--_Vicia_ (Vetch) has a filamentous style, hairy towards the tip, and a pod with many seeds; climbing by means of tendrils; the leaves have many leaflets.--_Faba_ (_F. vulgaris_, Horse-bean) is erect, without tendrils; its pod is thick with spongy septa between the seeds.--_Ervum_ (Lentil) has a pod with only 1–2 seeds, and sweeping hairs (stylar-brush) on the inner side of the style.--_Pisum_ (Pea; Fig. 512) has very large stipules, the bent style has a hollow groove on the anterior side. _P. sativum_ (Common Pea), _P. arvense_ (Grey Pea).--_Lathyrus_ (Sweet Pea) generally has an angular, winged stem and most frequently only a few pairs of leaflets. The style is flattened, with sweeping hairs on the back. ~In _L. aphaca_ the stipules alone are developed into foliage-leaves, while the remainder of the leaf is modified into a tendril.~--_Cicer_ has a nearly straight embryo and imparipinnate leaves with dentate or incised leaflets. _C. arietinus_ (Chick-pea).--~_Abrus_ (_precatorius_, etc.); the seeds (“Crab’s eyes,” “Paternoster peas,” “Jequirity”) are scarlet with a black spot round the hilum.~

=5.= PHASEOLEÆ. Herbs, twining or erect, but not climbing by tendrils; the leaves are imparipinnate, generally _ternate_, and bear small, linear bodies resembling stipules at the base of the stalks of the leaflets. The inflorescences are most frequently compound, groups of few flowers being situated on short, nodose, lateral axes borne on a longer stem. On germination the cotyledons are raised a considerable distance above the ground, and become greenish, but do not become leaf-like; in _P. multiflorus_ they remain underground. Stamens as in the Vetches.--_Phaseolus_ (Kidney-bean): the keel with the stamen and style is spirally _twisted_ (to the right). Herbs, twining to the left.--~The “Calabar-bean” (_Physostigma venenosum_), _Erythrina_, _Clitoria_, _Glycine_, _Soja_, _Mucuna_, _Apios_, _Canavalia_, _Vigna_, _Dolichos_, _Cajanus_, _Rhynchosia_, etc.~

=6.= TRIFOLIEÆ (CLOVERS). Herbs with _ternate_ leaves, the leaflets are often dentate with the veins prolonged into the teeth; stamens diadelphous; fruit 1-locular, 1–few-seeded, pyxidium-like, irregularly dehiscent, or more frequently a _nut_. The flowers are generally borne in capitula, racemes, or spikes.--_Trifolium_ (Clover). The corolla is gamopetalous. The calyx persists, together with the corolla, round the ripe fruit. The inflorescence is a spike, capitulum or capitate umbel; the leaves are ternate, and have adnate stipules.--_Medicago_ (Medick). The corolla falls off after flowering; fruit curved like a sickle or spirally twisted; it is a nut, and opens with difficulty. Leaves ternate.--_Melilotus_ (Melilot) has a small, spherical or lanceolate, thick and wrinkled fruit, which as a rule is indehiscent. The inflorescence is a raceme, often long, or a spike, sometimes a capitulum. Leaves ternate.--_Ononis_ (Rest-harrow) differs in having monadelphous stamens and in being more shrub-like and bushy, and in having a normal, 2-valved pod, by which characteristic it approaches the Genisteæ. The flowers are generally rose-coloured, solitary, or in few-flowered racemes in the leaf-axils. Thorns (branches) are often present; the leaves are compound with only one small leaflet (the terminal one), or ternate with adnate stipules.

=7.= LOTEÆ. Herbs with ternate or imparipinnate leaves, with entire leaflets. In the latter case, when the lowest pair of leaflets is placed quite close to the sheath, the stalk is wanting, and apparently a trifoliate leaf with large stipules is developed. Flowers in an umbel or capitulum. Stamens monadelphous or diadelphous, the filaments (either all of them, or only the 5 sepal-stamens) are widened at the top.--_Lotus_ (Bird’s-foot-trefoil) has a long, round pod.--_Tetragonolobus._--_Anthyllis_ (Lady’s-finger); the fruit is a nut, which is distributed by the wind by means of the membranous, bladder-like calyx, which completely encloses and falls off with it.

=8.= GENISTEÆ. The majority are shrubs or trees with apparently simple leaves, _i.e._ compound leaves with only one leaflet (the terminal leaflet), or ternate leaves; the stipules in most instances are very small or are entirely wanting; stamens monadelphous.--_Genista_ (Dyer’s-weed) has apparently simple leaves; the branches often terminate in a thorn. ~The strongly-winged stems in _G. sagittalis_ are its most important organs of assimilation. _Bossiæa rufa_ has flat branches, its leaves being reduced to small, pointed stipules.~--_Sarothamnus_ (Broom) has switch-like, angular branches and often both the apparently simple and ternate leaves on the same shoot; style spirally rolled.--_Cytisus_ (Laburnum). _Ulex_ (Furze; ~in _U. europæus_, the seedlings bear a few foliage leaves, but the leaves succeeding these are modified into thorns~); _Spartium_; _Crotalaria_, etc.--_Lupinus_ (Lupin) is allied to this group; it has a thick, often somewhat fleshy pod, and digitate leaves with adnate stipules.--_Retama._

=9.= HEDYSAREÆ are especially recognised by having the ovary divided by transverse septa into as many cells as there are seeds, the fruit thus becomes a _lomentum_, dehiscing transversely into nut-like joints (Fig. 513).--_Ornithopus_ (Bird’s-foot); _Coronilla_; _Hippocrepis_; _Onobrychis_ (Sainfoin) has a fruit with only 1 joint (_i.e._ a 1-seeded nut); _Desmodium_; _Alhagi_; _Hedysarum_, etc.--_Arachis hypogæa_ (Earth-nut) has a pod which is abstricted between the seeds, and is indehiscent, but is not multilocular nor a true lomentum; it is reticulately wrinkled externally, and ripens underground; the basal part of the ovary is prolonged after flowering, attaining a length of several inches, and buries the young fruit in the soil. The embryo is straight.--~_Desmodium gyrans_ is well-known for its motile leaflets.~