Of the second family (_Cæsalpineæ_), mainly tropical, the honey locust (_Gleditschia_) and red-bud (_Cercis_) (Fig. 115, _G_) are the commonest examples. The flowers differ mainly from the _Papilionaceæ_ in being less perfectly papilionaceous, and the stamens are almost entirely distinct (Fig. 115, _H_). The last family (_Mimosaceæ_) is also mainly tropical. The acacias, sensitive-plant (_Mimosa_), and the sensitive-brier of the southern United States (_Schrankia_) (Fig. 115, _I_) represent this family. The flowers are quite different from the others of the order, being tubular and the petals united, thus resembling the flowers of the _Sympetalæ_. The leaves of _Mimosa_ and _Schrankia_ are extraordinarily sensitive, folding up if irritated. CHAPTER XIX. CLASSIFICATION OF DICOTYLEDONS (_Continued_). DIVISION II.--_Sympetalæ_. The _Sympetalæ_ or _Gamopetalæ_ are at once distinguished from the _Choripetalæ_ by having the petals more or less united, so that the corolla is to some extent tubular. In the last order of the _Choripetalæ_ we found a few examples (_Mimosaceæ_) where the same thing is true, and these form a transition from the _Choripetalæ_ to the _Sympetalæ_. There are two great divisions, _Isocarpæ_ and _Anisocarpæ_. In the first the carpels are of the same number as the petals and sepals; in the second fewer. In both cases the carpels are completely united, forming a single, compound pistil. In the _Isocarpæ_ there are usually twice as many stamens as petals, occasionally the same number. There are three orders of the _Isocarpæ_, viz., _Bicornes_, _Primulinæ_, and _Diospyrinæ_. The first is a large order with six families, including many very beautiful plants, and a few of some economic value. Of the six families, all but one (_Epacrideæ_) are represented in the United States. Of these the _Pyrolaceæ_ includes the pretty little pyrolas and prince's-pine (_Chimaphila_) (Fig. 116, _J_); the _Monotropeæ_ has as its commonest examples, the curious Indian-pipe (_Monotropa uniflora_), and pine-sap (_M. hypopitys_) (Fig. 116, _L_). These grow on decaying vegetable matter, and are quite devoid of chlorophyll, the former species being pure white throughout (hence a popular name, "ghost flower"); the latter is yellowish. The magnificent rhododendrons and azaleas (Fig. 116, _F_), and the mountain laurel (_Kalmia_) (Fig. 116, _I_), belong to the _Rhodoraceæ_. The heath family (_Ericaceæ_), besides the true heaths (_Erica_, _Calluna_), includes the pretty trailing-arbutus or may-flower (_Epigæa_), _Andromeda_, _Oxydendrum_ (Fig. 116, _E_), wintergreen (_Gaultheria_), etc. The last family is represented by the cranberry (_Vaccinium_) and huckleberry (_Gaylussacia_).