_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.