CHAPTER XIX.
CLASSIFICATION OF DICOTYLEDONS (Continued).
Division II.—Sympetalæ.
The Sympetalæ or Gamopetalæ are at once distinguished from the Choripetalæ by having the petals more or less united, so that the corolla is to some extent tubular. In the last order of the Choripetalæ we found a few examples (Mimosaceæ) where the same thing is true, and these form a transition from the Choripetalæ to the Sympetalæ.
There are two great divisions, Isocarpæ and Anisocarpæ. In the first the carpels are of the same number as the petals and sepals; in the second fewer. In both cases the carpels are completely united, forming a single, compound pistil. In the Isocarpæ there are usually twice as many stamens as petals, occasionally the same number.
There are three orders of the Isocarpæ, viz., Bicornes, Primulinæ, and Diospyrinæ. The first is a large order with six families, including many very beautiful plants, and a few of some economic value. Of the six families, all but one (Epacrideæ) are represented in the United States. Of these the Pyrolaceæ includes the pretty little pyrolas and prince’s-pine (Chimaphila) ([Fig. 116], J); the Monotropeæ has as its commonest examples, the curious Indian-pipe (Monotropa uniflora), and pine-sap (M. hypopitys) ([Fig. 116], L). These grow on decaying vegetable matter, and are quite devoid of chlorophyll, the former species being pure white throughout (hence a popular name, “ghost flower”); the latter is yellowish. The magnificent rhododendrons and azaleas ([Fig. 116], F), and the mountain laurel (Kalmia) ([Fig. 116], I), belong to the Rhodoraceæ. The heath family (Ericaceæ), besides the true heaths (Erica, Calluna), includes the pretty trailing-arbutus or may-flower (Epigæa), Andromeda, Oxydendrum ([Fig. 116], E), wintergreen (Gaultheria), etc. The last family is represented by the cranberry (Vaccinium) and huckleberry (Gaylussacia).
Fig. 116.—Types of Isocarpous sympetalæ (Bicornes). A, flowers, fruit, and leaves of huckleberry, Gaylussacia (Vaccinieæ), × 1. B, vertical section of the flower, × 3. C, a stamen: i, from in front; ii, from the side, × 4. D, cross-section of the young fruit, × 2. E, flower of sorrel-tree, Oxydendrum (Ericaceæ), × 2. F, flower of azalea (Rhododendron), × ½. G, cross-section of the ovary, × 3. H, diagram of the flower. I, flower of mountain laurel (Kalmia), × 1. J, prince’s-pine, Chimaphila (Pyrolaceæ), × ½. K, a single flower, × 1. L, plant of pine-sap, Monotropa, (Monotropeæ), × ½. M, section of a flower, × 1.
The second order, the primroses (Primulinæ), is principally represented in the cooler parts of the world by the true primrose family (Primulaceæ), of which several familiar plants may be mentioned. The genus Primula includes the European primrose and cowslip, as well as two or three small American species, and the commonly cultivated Chinese primrose. Other genera are Dodecatheon, of which the beautiful shooting-star (D. Meadia) ([Fig. 117], A) is the best known. Something like this is Cyclamen, sometimes cultivated as a house plant. The moneywort (Lysimachia nummularia) ([Fig. 117], D), as well as other species, also belongs here.
