FAMILIES
Cruciferæ. Mustard Family.
Herbs with pungent, watery juice. Leaves.—Alternate; without stipules; entire or divided. Flowers.—Generally in racemes. Sepals.—Four. Petals.—Four; usually with narrowed base or claw; the blades spreading to form a cross. Stamens.—Six; two of them shorter than the other four. Ovary.—Two-celled; rarely one-celled. Style undivided, or none. Stigma entire or two-lobed. Fruit.—A silique—i.e. a capsule, in which the walls separate upward away from a central partition.
The Mustard family is a very large one, comprising over a hundred and seventy genera, and containing between one and two thousand species. It is widely distributed over all parts of the world, but is most abundantly represented in the cooler or temperate regions. It furnishes us with many useful plants; such as the mustard, horseradish, radish, cabbage, turnip, cauliflower, etc.
The genera of this order are very closely allied, and very difficult of discrimination. The fruit, as well as the flower, is necessary in the study of any given species.
Leguminosæ. Pea Family.
The order Leguminosæ is divided into three well-marked sub-orders—the Pea family proper, the Brasiletto family, and the Mimosa family. But as all our genera, save Cercis, fall under the first, we shall describe that only.
Papilionaceæ. Pea Family proper.
Herbs, shrubs, or trees. Leaves.—Usually alternate; compound; with stipules; the latter sometimes transformed into thorns or tendrils. Flowers.—Seldom solitary; usually in spikes, racemes or umbels. Calyx.—Five-toothed; often bilabiate. Corolla.—Irregular; of five petals; papilionaceous—i.e. the two lower petals more or less coherent, forming the keel; the two lateral ones often adherent to the keel, called the wings; the upper petal called the standard or banner. Stamens and pistil inclosed in the keel. Stamens.—Ten; their filaments either coherent into a tube surrounding the pistil; or nine of them united into a sheath, open above, the tenth lying in front of the cleft; or rarely all distinct. Ovary.—Superior; one-celled. Style.—Simple and incurved. Stigma.—Simple. Fruit.—A two-valved pod, of which the garden pea is typical.
The Pea family, including its three sub-orders, is one of the most important plant-families known. It is distributed over almost the entire world, and furnishes some of the most valuable products to man. The Judas-tree, the numerous acacias, and the sweet pea, are well known in our gardens; while among our most valuable vegetables are the bean, the pea, and the lentil. The clover and alfalfa are extremely important forage plants.
The order furnishes several important timber-trees, in different parts of the world, such as the Rosewood, the Laburnum, and the Locust; and yields numerous products of economic importance, such as licorice, senna, gum Senegal, gum Arabic, gum tragacanth, balsam of copaiba, balsam of Tolu, indigo, logwood, red sandalwood, etc.
Compositæ. Composite Family.
Herbs, rarely shrubs. Leaves.—Usually alternate; without stipules. Flowers.—In a close head on a common receptacle, surrounded by an involucre, whose divisions are called scales or bracts. Calyx-tube.—Adnate to the one-celled ovary; its limb (called a pappus) crowning its summit in the form of bristles, awns, scales, teeth, etc.; or cup-shaped; or else entirely absent. Corolla.—Either strap-shaped or tubular; in the latter chiefly five-lobed. Stamens.—Five (rarely four); on the corolla; their anthers united in a tube. Style.—Two-cleft at the apex. Fruit.—An akene. Flowers with strap-shaped corollas are called ray flowers or rays. The tubular flowers compose the disk.
The Composite family is the largest of all plant-families, numbering twelve thousand species and upward, and is widely distributed over the world. In the cooler parts of the world the plants are mostly herbaceous, but toward the tropics they gradually become shrubs, and even trees. In North America they comprise about one sixth of all the flowering plants.
For so large a family there are comparatively few useful plants found in it. Among the products of the order, may be mentioned chicory, lettuce, the artichoke, the vegetable oyster, arnica, chamomile-flowers, wormwood, absinth, elecampane, coltsfoot, taraxacum, oil of tansy, etc. But our gardens owe to this family innumerable beautiful and showy plants such as the China aster, the chrysanthemum, the cosmos, zinnia, dahlia, ageratum, gaillardia, coreopsis, sunflower, etc., etc.
The plants of this family are quickly recognized by the flowers being always borne in a head and surrounded by an involucre, and presenting the appearance of a single flower. The heads are sometimes made up entirely of one kind of flower. The dandelion and the chicory are examples of a head made up entirely of ray-flowers, while the thistle consists of tubular flowers only. The more common arrangement, however, is the mixed one, comprising both tubular disk-flowers and strap-shaped rays, as in the daisy. The seeds are usually furnished with silken down or a delicate parachute to waft them abroad.
The identification of the flowers of this order is a very difficult matter, even for experienced botanists.
Labiatæ. Mint Family.
Herbs with square stems. Leaves.—Opposite; usually aromatic. Flowers.—Axillary, or often in whorls or heads. Corolla.—Bilabiate (rarely regular). Stamens.—Four (or only two). Ovary.—Deeply four-lobed; becoming four seedlike nutlets. Style single; arising from the midst of the lobes.
The plants of this order are easily recognized by the traits in the above description. But some of these traits are shared by the plants of the Figwort family, which have also the bilabiate corolla. The distinguishing character, however, is always to be found in the four-lobed ovary for the Figworts have a two-celled ovary.
This order is a large one; and there are no noxious or poisonous plants to be found in it. On the contrary, it comprises many useful plants, too well known almost to need enumeration—such as the lavender, peppermint, sage, horehound, thyme, spearmint, horsemint, pennyroyal, etc.