_Rosaceæ_--Rose family. In the broad sense including, besides the rose, the strawberry, blackberry, apple, pear, peach, plum, besides many herbs with wholly dry fruits. There are always five petals, five lobes to the partly united calyx, but numerous stamens. They may be herbs, shrubs, or trees, with simple or compound leaves, but these are nearly always alternately arranged. There are over 100 genera and nearly 2,000 species. Because of the size of the Rosaceæ and differences in fruit, the apple and its relatives are often included in a separate family, the Malaceæ (Figure 96), and the peaches and plums in Amygdalaceæ. The general structure of the flower is sufficiently uniform, however, for them all to have been included in Rosaceæ (Figure 97). [Illustration: FIG. 96.--WASHINGTON THORN A prickly shrub related to the apple, which, with the plums, cherries, pears, strawberry, blackberry and hundreds of other plants are all grouped in the _Rosaceæ_ or rose family.] _Papilionaceæ_--Pea family. A large family having characteristic pealike flowers, a description of which has already been given in Chapter I. They all bear legumes, a pod that splits down one side, not both, as in Brassicaceæ. Besides the pea, the bean, vetch, alfalfa, lentil, locust tree, and dozens of valuable timber trees in the tropics belong here. Flowers all showy and absolutely dependent upon insects for fertilization. Seeds highly nutritious in many genera, and the roots of nearly all have bacteria associated with them. (See chapter on Food Habits of Plants.) Three hundred and twenty-five genera and over 5,000 species of wide distribution, but most frequent in the tropics. [Illustration: FIG. 97.--THIMBLEBERRY (_Rubus odoratus_) A bristly shrub of the Rose family common in rocky places in eastern North America.] There are many other smaller families in different parts of the world which hover, as it were, about these two giant plant families that make definite landmarks in the scheme of plant classification. The character of having partly united sepals and numerous stamens inserted around, or even above the ovary, give to all the flowers of the Rosaceæ and related plants a general family resemblance that is very striking. The pea family, and its relatives, also have flower and fruit characters of remarkable uniformity, considering the tremendous number of species. From this point on to the end of the polypetalæ there are scores of plant families, all agreeing in having a compound ovary, that is, one that is more than one-celled, and in also having quite distinct and separate sepals. Their agreement in these characters, however, ends all other evidences of relationship, and it is beyond the scope of this book to go into the details of each, or even a few of them. A list with some brief notes on those most important must suffice here.