Fig. 122.—Anisocarpous sympetalæ (Contortæ). A, flower of fringe-tree, Chionanthus (Oleaceæ), × 1. B, base of the flower, with part of the calyx and corolla removed, × 2. C, fruit of white ash, Fraxinus (Oleaceæ), × 1. D, flower of pink-root, Spigelia (Loganiaceæ), × ½. E, cross-section of the ovary, × 3. F, flower of fringed gentian, Gentiana (Gentianaceæ), × ½. G, diagram of the flower. H, flowering branch of dog-bane, Apocynum (Apocynaceæ), × ½. I, vertical section of a flower, × 2. J, bud. K, flower of milk-weed, Asclepias (Asclepiadaceæ), × 1. L, vertical section through the upper part of the flower, × 2. gy. pistil. p, pollen masses. an. stamen. M, a pair of pollen masses, × 6. N, a nearly ripe seed, × 1.
The last family is the milk-weeds (Asclepiadaceæ), which have extremely complicated flowers. Our numerous milk-weeds ([Fig. 122], K) are familiar representatives, and exhibit perfectly the peculiarities of the family. Like the dog-banes, the plants contain a milky juice which is often poisonous. Besides the true milk-weeds (Asclepias), there are several other genera within the United States, but mostly southern in their distribution. Many of them are twining plants and occasionally cultivated for their showy flowers. Of the cultivated forms, the wax-plant (Hoya), and Physianthus are the commonest.
Fig. 123.—Anisocarpous sympetalæ (Campanulinæ). A, vertical section of the bud of American bell-flower, Campanula (Campanulaceæ), × 2. B, an expanded flower, × 1. The stamens have discharged their pollen, and the stigma has opened. C, cross-section of the ovary, × 3. D, flower of the Carpathian bell-flower (Campanula Carpatica), × 1. E, flower of cardinal-flower, Lobelia (Lobeliaceæ), × 1. F, the same, with the corolla and sepals removed. an. the united anthers. gy. the tip of the pistil. G, the tip of the pistil, × 2, showing the circle of hairs surrounding the stigma. H, cross-section of the ovary, × 3. I, tip of a branch of cucumber, Cucurbita (Cucurbitaceæ), with an expanded female flower (♀). J, andrœcium of a male flower, showing the peculiar convoluted anthers (an.), × 2. K, cross-section of the ovary, × 2.
The fourth order (Campanulinæ) also embraces five families, but of these only three are represented among our wild plants. The bell-flowers (Campanula) ([Fig. 123], A, D) are examples of the family Campanulaceæ, and numerous species are common, both wild and cultivated.
