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.