Geraniaceæ—Geranium family. Includes also the common garden as well as the wild geranium. Fruit splitting into five parts. Leaves always divided or even dissected; 12 genera and 470 species, all herbs.
Anacardiaceæ—Includes the tree of heaven, sumac, poison ivy, and in the tropics, the mahogany, all trees, shrubs, or vines; 60 genera and 500 species, mostly in the tropics.
Malvaceæ—Mallow family, including, besides the marshmallow, the rose of Sharon, and cotton. They all have the stamens united into a column or tube which surrounds the style. About 40 genera and 900 species of herbs, shrubs, or trees of wide distribution.
Cactaceæ—Cactus family. Nearly all desert plants, with no leaves or practically none, and greenish stems that function as leaves and also store water. Of the greatest variety of form and always bearing numerous petals and fleshy fruits, of which the prickly pear is familiar enough. Of 40 genera and over 1,000 species, all, but a handful, come from North and South America.
Umbelliferæ (often called Ammiaceæ)—The climax of the polypetalous families, and nearly always bearing flowers in umbels. There are usually many flowers, sometimes several hundred in each cluster. Familiar examples are parsley, celery, parsnip, Queen Anne’s lace, and many others. The seeds often contain an aromatic oil, as in caraway, and some are violently poisonous, as the water hemlock. About 250 genera and over 2,000 species, all herbs, widely distributed, but most common in temperate regions.
We have seen from the foregoing the probable development of dicotyledonous plants from those simplest ones, where, as in the pines, there is merely a naked ovule between scales, through the catkin-bearing trees, without petals or sepals, and all wind-pollinated, to families where just an inconspicuous and, subsequently, a colored calyx is found, and after this the dawn of those plants that have complete and perfect flowers. Among the latter all those so far noted have separate petals, but after the Ammiaceæ, or carrot family, there appears a new character, setting off practically all other dicotyledonous plants from those already treated. This new character—and hints of it are found before it reaches the perfection found in the subsequently described families—is that of the petals being united to form some sort of a connected or, more often, a tubular corolla. The petals are represented merely by the lobes of the corolla, mostly four or five, and in many families of this group, known as the gamopetalæ, literally, united petals, this tubular corolla is irregular and often beautifully formed. In salvia, for instance, there is a hoodlike upper part overhanging the lower tubular part. Other familiar examples of these irregular corollas are the garden snapdragon, Oswego tea, skullcap, pentstemon, and many others.
(c) Gamopetalæ—The earlier families among those generally having united petals seem not yet quite sure of their new character, for a few of them hark back to the condition of having, in some genera, quite separate petals. One of the first families in this series, the Ericaceæ ([Figure 98]), or heath family, has several genera in which this is true, notably in the Labrador tea and the sand myrtle among native plants, and some foreign relatives. The Ericaceæ are almost exclusively shrubs or trees, but some of our native sorts, such as trailing arbutus and wintergreen, are practically herblike, although they are, strictly speaking, woody plants. The family is remarkable for containing beautiful flowered garden plants, such as the hundreds of species of South African heaths, the heather, the azaleas and rhododendrons, and our beautiful native Rhodora, about which Emerson wrote one of his most beautiful poems. The flowers in the heath family are often perfectly regular and bell-shaped, but sometimes irregular, as in azaleas and several other genera. Nearly all the family rely on microscopic organisms to get their food, and some close relatives, like the Indian pipe, are saprophytes. There are over 70 genera and 1,200 species widely distributed. Central Asia is the home of most rhododendrons and azaleas, scores of species being found in the upper reaches of the Himalayas.
The Ericaceæ are typical of many families in the first group of the gamopetalæ, in that all of them, with a few exceptions like the cranberry, have a superior ovary. That is, the petals and sepals arise from the base or below the ovary, and consequently the mature fruit in such plants is never crowned with the remains of the withered calyx, as blueberries always are and all other gamopetalæ that have an inferior ovary. The character of having an inferior or superior ovary separates the gamopetalæ into two large groups of families, the heath family and many others, with superior ovary, and a few but numerically very important families that always have an inferior ovary.