Fig. 103.—Types of Aphanocyclæ (Rhœdinæ). A, plant of blood-root, Sanguinaria (Papaveraceæ), × ⅓. B, a single flower, × 1. C, fruit, × ½. D, section of the seed. em. embryo, × 2. E, diagram of the flower. F, flower of Dutchman’s breeches, Dicentra (Fumariaceæ), × 1. G, group of three stamens of the same, × 2. H, one of the inner petals, × 2. I, fruit of celandine poppy, Stylophorum (Papaveraceæ), × ½. J, flower of mustard, Brassica (Cruciferæ), × 1. K, the same, with the petals removed, × 2. L, fruit of the same, × 1.
The second family, the fumitories (Fumariaceæ) are delicate, smooth plants, with curious flowers and compound leaves. The garden bleeding-heart (Dicentra spectabilis) and the pretty, wild Dicentras ([Fig. 103], F) are familiar to nearly every one.
Other examples are the mountain fringe (Adlumia), a climbing species, and several species of Corydalis, differing mainly from Dicentra in having the corolla one-sided.
The mustard family (Cruciferæ) comprises by far the greater part of the order. The shepherd’s-purse, already studied, belongs here, and may be taken as a type of the family. There is great uniformity in all as regards the flowers, so that the classification is based mainly on differences in the fruit and seeds. Many of the most valuable garden vegetables, as well as a few more or less valuable wild plants, are members of the family, which, however, includes some troublesome weeds. Cabbages, turnips, radishes, with all their varieties, belong here, as well as numerous species of wild cresses. A few like the wall-flower (Cheiranthus) and stock (Matthiola) are cultivated for ornament.
The last family is the caper family (Capparideæ), represented by only a few not common plants. The type of the order is Capparis, whose pickled flower-buds constitute capers.
The fourth order (Cistifloræ) of the Aphanocyclæ is a very large one, but the majority of the sixteen families included in it are not represented within our limits. The flowers have the sepals and petals in fives, the stamens either the same or more numerous.
Fig. 104.—Types of Aphanocyclæ (Cistifloræ). A, flower of wild blue violet, Viola (Violaceæ), × 1. B, the lower petal prolonged behind into a sac or spur, × 1. C, the stamens, × 2. D, pistil, × 2. E, a leaf, × ½. F, section of the ovary, × 2. G, the fruit, × 1. H, the same after it has opened, × 1. I, diagram of the flower. J, flower of mignonette, Reseda (Resedaceæ), × 2. K, a petal, × 3. L, cross-section of the ovary, × 3. M, fruit, × 1. N, plant of sundew, Drosera (Droseraceæ), × ½. O, a leaf that has captured a mosquito, × 2. P, flower of another species (D. filiformis), × 2. Q, cross-section of the ovary, × 4.
Among the commoner members of the order are the mignonettes (Resedaceæ) and the violets (Violaceæ), of which the various wild and cultivated species are familiar plants ([Fig. 104], A, M). The sundews (Droseraceæ) are most extraordinary plants, growing in boggy land over pretty much the whole world. They are represented in the United States by several species of sundew (Drosera), and the still more curious Venus’s-flytrap (Dionæa) of North Carolina. The leaves of the latter are sensitive, and composed of two parts which snap together like a steel trap. If an insect lights upon the leaf, and touches certain hairs upon its upper surface, the two parts snap together, holding the insect tightly. A digestive fluid is secreted by glands upon the inner surface of the leaf, and in a short time the captured insect is actually digested and absorbed by the leaves. The same process takes place in the sundew ([Fig. 104], N) where, however, the mechanism is somewhat different. Here the tentacles, with which the leaf is studded, secrete a sticky fluid which holds any small insect that may light upon it. The tentacles now slowly bend inward and finally the edges of the leaf as well, until the captured insect is firmly held, when a digestive process, similar to that in Dionœa, takes place. This curious habit is probably to be explained from the position where the plant grows, the roots being in water where there does not seem to be a sufficient supply of nitrogenous matter for the wants of the plant, which supplements the supply from the bodies of the captured insects.