Fig. 120.—Anisocarpous sympetalæ (Labiatifloræ). A, dead nettle, Lamium, (Labiatæ), × ½. B, a single flower, × 1. C, the stamens and pistil, × 1. D, cross-section of the ovary, × 2. E, diagram of the flower; the position of the absent stamen is indicated by the small circle. F, fruit of the common sage, Salvia (Labiatæ), × 1. Part of the persistent calyx has been removed to show the four seed-like fruits, or nutlets. G, section of a nutlet, × 3. The embryo fills the seed completely. H, part of an inflorescence of figwort, Scrophularia (Scrophularineæ), × 1. I, cross-section of the young fruit, × 2. J, flower of speedwell, Veronica (Scrophularineæ), × 2. K, fruit of Veronica, × 2. L, cross-section of K. M, flower of moth-mullein, Verbascum (Scrophularineæ), × ½. N, flower of toad-flax, Linaria (Scrophularineæ), × 1. O, leaf of bladder-weed, Utricularia (Lentibulariaceæ), × 1. x, one of the “traps.” P, a single trap, × 5.
The Scrophularineæ differ mainly from the Labiatæ in having round stems, and the ovary not splitting into separate one-seeded fruits. The leaves are also sometimes alternate. There are generally four stamens, two long and two short, as in the labiates, but in the mullein (Verbascum) ([Fig. 120], M), where the flower is only slightly zygomorphic, there is a fifth rudimentary stamen, while in others (e.g. Veronica) ([Fig. 120], J) there are but two stamens. Many have large, showy flowers, as in the cultivated foxglove (Digitalis), and the native species of Gerardia, mullein, Mimulus, etc., while a few like the figwort, Scrophularia ([Fig. 120], H), and speedwells (Veronica) have duller-colored or smaller flowers.
Fig. 121.—Anisocarpous sympetalæ (Labiatifloræ). A, flowering branch of trumpet-creeper, Tecoma (Bignoniaceæ), × ¼. B, a single flower, divided lengthwise, × ½. C, cross-section of the ovary, × 2. D, diagram of the flower. E, flower of vervain, Verbena (Verbenæ), × 2: i, from the side; ii, from in front; iii, the corolla laid open. F, nearly ripe fruit of the same, × 2. G, part of a spike of flowers of the common plantain, Plantago (Plantagineæ), × 1; The upper flowers have the pistils mature, but the stamens are not yet ripe. H, a flower from the upper (younger) part of the spike. I, an older expanded flower, with ripe stamens, × 3.
The curious bladder-weed (Utricularia) is the type of the family Lentibulariaceæ, aquatic or semi-aquatic plants which possess special contrivances for capturing insects or small water animals. These in the bladder-weed are little sacs ([Fig. 120], P) which act as traps from which the animals cannot escape after being captured. There does not appear to be here any actual digestion, but simply an absorption of the products of decomposition, as in the pitcher-plant. In the nearly related land form, Pinguicula, however, there is much the same arrangement as in the sundew.
The family Gesneraceæ is mainly a tropical one, represented in the greenhouses by the magnificent Gloxinia and Achimenes, but of native plants there are only a few parasitic forms destitute of chlorophyll and with small, inconspicuous flowers. The commonest of these is Epiphegus, a much-branched, brownish plant, common in autumn about the roots of beech-trees upon which it is parasitic, and whence it derives its common name, “beech-drops.”
The bignonia family (Bignoniaceæ) is mainly tropical, but in our southern states is represented by the showy trumpet-creeper (Tecoma) ([Fig. 121], A), the catalpa, and Martynia.
The other plants likely to be met with by the student belong either to the Verbenaceæ, represented by the showy verbenas of the gardens, and our much less showy wild vervains, also belonging to the genus Verbena ([Fig. 121], E); or to the plantain family (Plantagineæ), of which the various species of plantain (Plantago) are familiar to every one ([Fig. 121], G, I). The latter seem to be forms in which the flowers have become inconspicuous, and are wind fertilized, while probably all of its showy-flowered relatives are dependent on insects for fertilization.
The third order (Contortæ) of the Anisocarpæ includes five families, all represented by familiar forms. The first, the olive family (Oleaceæ), besides the olive, contains the lilac and jasmine among cultivated plants, and the various species of ash (Fraxinus), and the pretty fringe-tree (Chionanthus) ([Fig. 122], A), often cultivated for its abundant white flowers. The other families are the Gentianaceæ including the true gentians (Gentiana) ([Fig. 122], F), the buck-bean (Menyanthes), the centauries (Erythræa and Sabbatia), and several other less familiar genera; Loganiaceæ, with the pink-root (Spigelia) ([Fig. 122], D), as the best-known example; Apocynaceæ including the dog-bane (Apocynum) ([Fig. 122], H), and in the gardens the oleander and periwinkle (Vinca).