224 FAMILIES OF FLOWERING PLANTS 



Chaptee XXXI. — Order Pohmoniales or Tuhifiorae. 



This order consists mainly of herbs. It embraces twenty families, 

 of which the most important are the Convolvulaceae, Polemoniaceae, 

 Hydrophyllaceae, Boraginaceae, Verbenaceae, Labiatae, Solanaceae, 

 Scrophnlariaceae, Bignoniaceae and Acanthaceae. The corolla is gam- 

 opetalous throughout, with the stamens more or less united with its 

 tube. The ovary is superior and compound. 



Family Convolvulaceae. Morning-glory Family. Contains about 40 

 genera and nearly 1,000 species, of wide distribution. They are herbs 

 or vines, rarely shrubs or trees, with alternate leaves and axillarj^ 

 flowers. The calyx is usually persistent, the 5-angled or 5-lobed corolla 

 convolute (twisted) in the bud. Stamens, 5 ; ovary, 2-3-celled, becoming 

 a 2-4-valved capsule. 



The two most important genera. Convolvulus and Tpomoea are highly 

 esteemed as furnishing many ornamental vines. In fact, there is prob- 

 ably no genus in which the species are more uniformly handsome- 

 flowered throughout than the Tpomoea, to which the common morning- 

 glory belongs. (Fig. 194). The leaves are of every conceivable shape and 

 degree of lobation, while the flowers exhibit a great variety of colors, par- 

 ticularly in the tropics. The beautiful white moonflower, formerly in- 

 cluded in Tpomoea, is now usually placed in a distinct genus [Calonyciion). 

 The Convolvulaceae are of very slight economic importance; the gum-resin 

 known as scammony, is produced by Convolvulus Scanmionia, while the 

 purgative drug jalap is yielded by a species of Tpomoea. 



Family Cuscutaceae. Dodder Family, These are leafless parasitic 

 twining vines, all comprised in the single genus Cuscuta, of which there 

 are about 100 species, of wide distribution. The calyx and corolla are 

 5-lobed or 5-parted, the coralla-lobes frequently bearing scales alternate 

 with them. The stamens are 5 ; ovary 2-celled, becoming a 1-4-seeded 

 capsule. 



The seeds of the dodder germinate in the ground like those of ordi- 

 nary plants, and the young seedling soon attaches itself by means of 

 numerous minute suckers to the adjacent herbage. When it has ob- 

 tained a sufficient hold to enable it to secure the required amount of 

 nutrition its root and loAver portion perish. When fully grown it 

 resembles a mass of white or orange-colored tangled threads spread 

 over the foliage of the herbs on which it is found. While some species, 

 like C. Gronovii, are quite cosmopolitan in their tastes, occurring on a 

 variety of plants, others, like C. TrifoUi, are confined strictly to one 

 kind of plant. 



Family Polemoniaceae. Polemonium Family. This group, con- 

 sisting entirely of herbs, includes about 10 genera and 200 species, by 



