[Illustration: FIG. 123.--_Anisocarpous sympetalæ_ (_Campanulinæ_). _A_, vertical section of the bud of American bell-flower, _Campanula_ (_Campanulaceæ_), × 2. _B_, an expanded flower, × 1. The stamens have discharged their pollen, and the stigma has opened. _C_, cross-section of the ovary, × 3. _D_, flower of the Carpathian bell-flower (_Campanula Carpatica_), × 1. _E_, flower of cardinal-flower, _Lobelia_ (_Lobeliaceæ_), × 1. _F_, the same, with the corolla and sepals removed. _an._ the united anthers. _gy._ the tip of the pistil. _G_, the tip of the pistil, × 2, showing the circle of hairs surrounding the stigma. _H_, cross-section of the ovary, × 3. _I_, tip of a branch of cucumber, _Cucurbita_ (_Cucurbitaceæ_), with an expanded female flower (♀). _J_, andrœcium of a male flower, showing the peculiar convoluted anthers (_an._), × 2. _K_, cross-section of the ovary, × 2.] The fourth order (_Campanulinæ_) also embraces five families, but of these only three are represented among our wild plants. The bell-flowers (_Campanula_) (Fig. 123, _A_, _D_) are examples of the family _Campanulaceæ_, and numerous species are common, both wild and cultivated. [Illustration: FIG. 124.--_Anisocarpous sympetalæ_ (_Aggregatæ_). _A_, flowering branch of _Houstonia purpurea_, × 1 (_Rubiaceæ_). _B_, vertical section of a flower, × 2. _C_, fruit of bluets (_Houstonia cœrulea_), × 1. _D_, cross-section of the same. _E_, bedstraw, _Galium_ (_Rubiaceæ_), × ½. _F_, a single flower, × 2. _G_, flower of arrow-wood, _Viburnum_ (_Caprifoliaceæ_), × 2. _H_, the same, divided vertically. _I_, flowering branch of trumpet honeysuckle, _Lonicera_ (_Caprifoliaceæ_), × ½. _J_, a single flower, the upper part laid open, × 1. _K_, diagram of the flower. _L_, part of the inflorescence of valerian, _Valeriana_, (_Valerianeæ_), × 1. _M_, young; _N_, older flower, × 2. _O_, cross-section of the young fruit; one division of the three contains a perfect seed, the others are crowded to one side by its growth. _P_, inflorescence of teasel, _Dipsacus_ (_Dipsaceæ_), × ¼. _fl._ flowers. _Q_, a single flower, × 1. _R_, the same, with the corolla laid open.] The various species of _Lobelia_, of which the splendid cardinal-flower (_L. Cardinalis_) (Fig. 123, _E_) is one of the most beautiful, represent the very characteristic family _Lobeliaceæ_. Their milky juice contains more or less marked poisonous properties. The last family of the order is the gourd family (_Cucurbitaceæ_), represented by a few wild species, but best known by the many cultivated varieties of melons, cucumbers, squashes, etc. They are climbing or running plants, and provided with tendrils. The flowers are usually unisexual, sometimes diœcious, but oftener monœcious (Fig. 123, _I_).