Part 70

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.

Lythrum (Loose-strife). The flower is diplostemonous and 6-merous, with a long, tubular receptacle with epicalyx-teeth (Fig. 519 c). The 12 stamens are arranged in two tiers on the inner side of the receptacle. The gynœceum is bicarpellary. ~The flowers are borne in small dichasia in the leaf-axils, and their number is increased by accessory inflorescences beneath the main inflorescence.--The native species, L. salicaria, is trimorphic (long-styled, mid-and short-styled forms, Fig. 520). Cross-pollination is chiefly effected by humble-bees and bees, which seek the nectar formed at the bottom of the receptacle. Other species are only dimorphic, or even monomorphic.~--Closely allied are, Nesæa, Diplusodon, Lagerstrœmia, and Cuphea, whose flower resembles that of Lythrum, but is zygomorphic. In Cuphea the receptacle is oblique and at the back prolonged into a spur, in which the nectar, secreted by a gland situated behind the ovary, is collected; the calyx and corolla gradually become reduced in size toward the anterior side of the flower; the reverse, however, is the case with the 11 stamens (the posterior one is absent); the posterior loculus in the bilocular ovary is sometimes barren; the fruit, when ripe, dehisces along the posterior side, the ovary as well as the wall of the receptacle being ruptured by the placenta, which expands and projects freely. ~The flowers stand singly in the centre of the stem, between the pairs of leaves. This may be explained as follows: of the two foliage-leaves in each pair, one supports a foliage-shoot, the other a flower; the foliage-shoot remains in the axil, but the flower is displaced through the length of an entire internode to the next pair of leaves, and then assumes a position between these two leaves. All foliage-shoots stand in two rows, the flowers in two other rows.~

Peplis (Water-purslane), a small, annual plant, with thin, bell-shaped receptacle without projecting nerves. The small flowers have no petal-stamens, and often also no corolla; fruit indehiscent.--Ammannia is closely allied to it.

365 species; 30 genera; mostly in the Tropics, and more especially S. Am.--Some yield dyes, e.g. Lawsonia inermis (cultivated in Africa and Asia) and Lagerstrœmeria indica; some contain tannin; others are ornamental plants, especially in gardens in warm countries.

Order 2. =Blattiaceæ.= 12 species. Tropical Asia and Africa. Trees. Formerly included with Punica, but best placed as an independent order.

Order 3. =Melastomaceæ.= A very natural and very large order (150 genera; 2,500 species), its home being chiefly in tropical S. America, especially the Brazils (termed by Schouw “The kingdom of Palms and Melastomaceæ”). There are both herbaceous and arborescent species, which are easily recognized by the opposite or verticillate, simple leaves which have (with the exception of a few heather-like species) 3–5–7–9 curved veins proceeding from the base of the leaf, and connected very regularly by closely parallel, transverse veins. The flower is perigynous or epigynous; its type is that of the Onagraceæ (4–5-merous; 1 whorl of sepals, petals and carpels, 2 of stamens); the calyx is valvate, the corolla is twisted (to the left) in æstivation; the stamens are very characteristic; in the bud they are geniculate; the anther opens in the often long, beak-like, prolonged point, with 1, less frequently with 2 pores, and has generally ear-like appendages at its base. The fruit is a berry or capsule. These large and beautiful flowering-plants play a very important part in South American landscapes; otherwise they are of slight importance (a few are cultivated in conservatories, e.g. Centradenia, Medinilla, Lasiandra, Tibouchina, Miconia, etc.).

Order 4. =Œnotheraceæ= (or =Onagraceæ=). The flowers are arranged in racemes or spikes, ☿, epigynous, regular, polypetalous, =4=-merous in all 5 whorls (1 whorl of sepals, petals and carpels, 2 of stamens); 2–3–5–6-merous flowers are less frequent; the calyx is valvate, the corolla twisted in æstivation (the left edge being covered). Gynœceum simple with multilocular ovary; the style is undivided, filiform, and bears a capitate or 4-partite stigma; endosperm wanting; embryo straight.--The majority are herbs, especially water- and marsh-plants; several are shrubs. No essential oils. The leaves are alternate or opposite, always single, and without (or with very small) stipules. ~The odourless flowers sometimes have a coloured calyx. In some instances (e.g. Œnothera, Fuchsia) the receptacle is prolonged more or less beyond the inferior ovary, and finally falls off. The stamens are obdiplostemonous (carpels epipetalous); the petal-stamens are sometimes suppressed. The anthers in some genera are divided into storeys. The well-pronounced, triangular pollen-grains are connected together by viscous threads. Small stipules are sometimes found, e.g. Fuchsia, Lopezia.~

=A.= =Fruit a capsule.= Œnothera (Evening Primrose) is 4-merous, has 8 stamens, a tubular receptacle, and an oblong capsule with loculicidal dehiscence leaving a centrally placed column, bearing the seeds.--Epilobium (Willow-herb) deviates from Œnothera especially in the seeds being hairy (at the chalazal end of the seed).--Chamænerium is a Willow-herb with zygomorphic flowers.--~The following may be included here: Clarkia, Eucharidium (an Œnothera with 4 stamens and 3-lobed petals), Godetia and Boisduvalia, Jussiæa (dehiscence septicidal), Isnardia (petal-stamens absent, sometimes the petals also).--Lopezia has a peculiar, zygomorphic flower (Fig. 521); one of the four sepals is bent forwards and the other 3 backwards; the posterior petals are narrower than the 2 anterior ones which are turned obliquely backwards and bent like a knee, with a greenish nectary at the bend; 2 stamens, one only fertile (the posterior), while the anterior is barren, petaloid, and spoon-shaped; both are sensitive, which is essential for pollination. In Fig. 521, a represents an early stage, in which the stamen and style lie concealed in the staminode; b is the ♂ stage, the stamen projects from the centre of the flower; c, the ♀ stage, the style occupies the place of the stamen.~

=B.= =Fruit a berry.= Fuchsia generally has a coloured calyx and tubular receptacle; the corolla may be wanting.

=C.= =Fruit a nut.= Circæa (Enchanter’s Nightshade) has a 2-merous flower (S2, P2, A2 + 0 [petal-stamens are wanting], G2). The flowers are borne in racemes without bracts.--Gaura.

=D.= =Fruit a drupe.= Trapa (Horn-nut); a peculiar aquatic plant; the submerged stem has long internodes and lanceolate leaves, falling off at an early period, but at each node are found 4 long roots with thin, lateral roots (sometimes erroneously regarded as leaves) borne pinnately; the stem reaching the surface of the water, bears a rosette of rhombic foliage-leaves, with large, inflated stalks containing air, and forming the floating apparatus of the plants. In the axils of the leaves (as in Gunnera) 8 small, stipular structures are present. The flowers are solitary in the axils of the foliage-leaves (S4, P4, A4 + 0, G2), semi-epigynous. There is an 8-lobed, crenate disc on the free portion of the ovary; one ovule in each loculus. The fruit is a drupe with 4 (or 2) prominent horns (the persistent sepals), which after the pulp has decayed away bear a series of hooks turned downwards on each side, i.e. sclerenchymatous bundles which formerly lay concealed in the pulp of the sepals. ~The germination is peculiar: one of the cotyledons is large, and its thick extremity remains in the fruit, the other however is small and is pushed out at the apex of the fruit together with the radicle and plumule; the development of the root soon ceases, and the plumule usually grows into a stem entirely without branches, similar to the one described above, only that 1–2 precisely similar shoots arise in the axil of each cotyledon, so that each embryo produces 3–5 shoots.--Trapa, by its mode of life, its 1-seeded fruit, etc., forms a transition to Haloragidaceæ.~

The large-flowered forms are adapted for insect-pollination and are often protandrous, the small-flowered ones are homogamous and may pollinate themselves. Œnothera is adapted for hawk-moths and bees.--330 species; especially in temperate climates, chiefly in the Northern Hemisphere. Epilobium, Circæa are natives of this country; Trapa is extinct in this country, it has been found in a semi-fossilized condition near Cromer and in bogs in Denmark, and existed in Sweden until a few years ago; Œnothera has been introduced from N. Am.--A number of N. Am. species are grown as ornamental plants in our gardens. The seeds of Trapa natans are edible, and used as food in China.

Order 5. =Haloragidaceæ.= This is a reduced form of the Œnotheraceæ, and principally differs from these in the presence of endosperm and free styles. Only 1 ovule in each loculus.--84 species distributed over the entire globe; the majority are aquatic plants. The most advanced type is Myriophyllum (Water-Milfoil), with a regular, epigynous flower (S4, P4, A4 + 4, G4), most frequently diclinous (monœcious); the fruit is a 2–4-partite schizocarp. Aquatic plants, most frequently with pectinate, pinnate leaves.--Haloragis.--~Gunnera (a dozen species from the Southern Hemisphere) forms the next step in the reduction. Large, scattered, rough-haired, and softly-spined leaves, with small flowers in crowded inflorescences. The flower, when most complete, has S2, P2, A2 (petal-stamens) and G2, forming an inferior, unilocular ovary with 1 ovule. It is remarkable for the great number of stipules placed in transverse rows in the leaf-axils, for the peculiar glandular organs, and for the colonies of Nostoc, which are found embedded in the cortex as a kind of parasite.~--The simplest form is Hippuris (Mare’s-tail) with an extremely small, crenate or entire calyx, without corolla, and with only one stamen and one carpel, forming an inferior, unilocular ovary with only one ovule. Fruit a drupe with thin pulp. ~It is an aquatic plant with creeping, sympodial rhizome, and erect unbranched shoots, bearing numerous small, verticillate leaves. The small flowers are situated singly in the leaf-axils.~

Order 6. =Rhizophoraceæ.= Tropical trees or shrubs (50 species, the best known being Rhizophora mangle, Mangrove) which grow gregariously, especially along the banks of rivers and by sea-coasts, where the water is quiet and brackish, and where they form the so-called Mangrove-swamps. Aerial roots are formed on the stems and branches (Fig. 522 A). The seeds germinate in the fruit, which by arrest contains only one seed (Fig. 522 B), before it is detached from the tree. The radicle projects considerably from the seed, and hangs down freely in the air; when the embryo is finally detached from the mother-plant, the separation is effected by the hood-like cotyledon, which entirely envelops the plumule, becoming detached from the rest of the embryo, which falls down, while the hood-like cotyledon remains enclosed in the fruit. The embryo, after it has fallen, strikes root, and continues growing in the undisturbed mud under the trees, or perhaps it may first be drifted about by the water, being well adapted for this by its peculiar, tough nature, and large, intercellular spaces.--It may also further be remarked that the anther is divided into a number of small loculi. The leaves are stipulate. The endosperm projects from the micropyle, growing out from the base of the seed, and thus serves as an organ of suction to convey nutriment to the embryo from the mother-plant.

Order 7. =Combretaceæ.= Trees and shrubs, partly lianes. An inferior, unilocular ovary with few pendulous ovules. Conocarpus and Laguncularia form, in conjunction with the species of Rhizophoraceæ, the tropical Mangrove-swamps. Terminalia.--280 species; Tropics.

Order 8. =Myrtaceæ (Myrtles).= The plants belonging to this order are shrubs or trees, the majority being easily recognised by the vegetative characters. The leaves, for instance, are most frequently opposite, without stipules, undivided and entire, parchment-like or leathery, evergreen, aromatic, finely dotted by pellucid glands containing essential oils; the venation is penninerved with a nerve just inside and running parallel to the edge of the leaf. The flowers are regular, epigynous (Figs. 523, 524, 525) and ☿, most frequently =4-= or 5-merous in the calyx and corolla, with many stamens (by splitting, so that they are often in several distinct bundles) and an ovary with one style, formed of 2–5–many carpels; the receptacle is most frequently united for its entire length with the ovary. The fruit varies, but is most frequently a berry. The embryo is thick, often curved, with united cotyledons; no endosperm.

=1.= MYRTEÆ, MYRTLE GROUP. Chiefly American, though some are found also in Africa and Asia. The fruit is a berry with generally 2–5 loculi in the ovary, and many ovules in each.--Myrtus; Eugenia (the petals fall off together as a hood in the Clove, E. caryophyllata, Figs. 523, 524); Myrcia; Jambosa; Amomis; Psidium, etc.

=2.= PUNICEÆ, POMEGRANATE GROUP. Only 2 species (Punica granatum; from Persia, Afghanistan), differing in several respects from the typical form of the Myrtaceæ. The leaves are generally opposite, without glands and marginal veins. The receptacle, calyx and corolla are red; the latter 5–8–(generally 6-) merous. Calyx valvate and corolla folded as in Lythraceæ, stamens also and epicalyx as in this order. The most characteristic feature is the inferior, spherical berry, with dry pericarp, formed from two whorls of carpels in two tiers (Fig. 525); the interior whorl, which is also the lower, has 3 carpels, and the placentæ are situated in the inner angles of the 3 loculi; the external whorl is 5-merous, and the placentæ have originally the same position in the inner angles of the loculi, but their position is changed to the outer side of the loculi owing to the growth of the wall of the ovary, which takes place early, causing the carpels to become, as it were, turned inside out, so that the part which was turned downwards is turned upwards, and the part which was turned inwards becomes turned outwards (as in Mesembrianthemum). The edible part of the fruit is the fleshy testa, as in Ribes. The cotyledons are rolled together spirally.

FIG. 523.--Flowers (nat. size).

FIG. 524.--A bud (“clove”), long. sec. (mag.).]

=3.= LECYTHIDEÆ. The majority are South American. The leaves are scattered, without pellucid glands, and frequently dentate. The flowers are zygomorphic. The woody fruits are either indehiscent, or open by a lid. To this belong: Bertholletia (B. excelsa), the seeds well known as “Brazil-nuts,” Lecythis (Sapucaia-nuts from L. ollaria), Barringtonia.

=4.= LEPTOSPERMEÆ. Almost entirely from Australia and the East Asian and Pacific Islands. The fruit is a capsule. The leaves are scattered, and in some placed edgewise by the twisting of the leaf-stalks.--Eucalyptus, the Australian Gum-tree; the calyx falls off like a lid (Figs. 526, 527). Some of the species attain gigantic heights, E. amygdalina 140–150 m. with a diameter of 8 m. The leaves in E. globulus are opposite and dorsiventral on the young plant; on the older scattered, placed edgewise by the twisting of the leaf-stalk, and isolateral; Metrosideros, Calothamnus (stamens distinctly polyadelphous), Melaleuca, Leptospermum, Callistemon (the flowers are borne in spikes whose axis continues to grow after flowering, thus several zones of fruits may be seen on the same branch).

FIG. 526.--Long. sect. of flower.

FIG. 527.--Flower opening.]

=5.= CHAMÆLAUCIEÆ. Australian shrubs with heath-like appearance; they differ from the other Myrtaceæ in having a unilocular ovary with few, basal ovules, and a 1-seeded nut. The sepals are often pappus-like, and divided into many bristles.--Chamælaucium, Darwinia, etc.