Fig. 443.—Inflorescence of Tilia, with its winged bracteole (h); a, a axis of the shoot; the vegetative bud is seen between the inflorescence and the axis of the shoot; b petiole of foliage-leaf.
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.
Fig. 444.—Diagram of the inflorescence of Tilia and the vegetative bud; the position of the leaves is indicated, and also the position of the inflorescences, which develop from their axils in the following year.
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.
Fig. 445.—Longitudinal section through the flower of Malva silvestris.
