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.
Fig. 519.—Lythrum salicaria. c the “epicalyx.”
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.
