hern 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 _Sympetalae_. The leaves of _Mimosa_ and
_Schrankia_ are extraordinarily sensitive, folding up if irritated.

CHAPTER XIX.

CLASSIFICATION OF DICOTYLEDONS (_Continued_).

DIVISION II.--_Sympetalae_.

The _Sympetalae_ or _Gamopetalae_ are at once distinguished from the
_Choripetalae_ by having the petals more or less united, so that the
corolla is to some extent tubular. In the last order of the
_Choripetalae_ we found a few examples (_Mimosaceae_) where the same
thing is true, and these form a transition from the _Choripetalae_ to
the _Sympetalae_.

There are two great divisions, _Isocarpae_ and _Anisocarpae_. 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 _Isocarpae_ there are usually
twice as many stamens as petals, occasionally the same number.

There are three orders of the _Isocarpae_, viz., _Bicornes_,
_Primulinae_, and _Diospyrinae_. 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 (_Epacrideae_) are
represented in the United States. Of these the _Pyrolaceae_ includes
the pretty little pyrolas and prince's-pine (_Chimaphila_) (Fig. 116,
_J_); the _Monotropeae_ 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
_Rhodoraceae_. The heath family (_Ericaceae_), besides the true heaths
(_Erica_, _Calluna_), includes the pretty trailing-arbutus or
may-flower (_Epigaea_), _Andromeda_, _Oxydendrum_ (Fig. 116, _E_),
wintergreen (_Gaultheria_), etc. The last family is represented by the
cranberry (_Vaccinium_) and huckleberry (_Gaylussacia_).

[Illustration: FIG. 116.--Types of _Isocarpous sympetalae_
(_Bicornes_). _A_, flowers, fruit, and leaves of huckleberry,
_Gaylussacia_ (_Vaccinie