THE CON VOLT UIiT7S FAMILY. 229 



LXV.— THE CONVOLVULUS FAMILY. Convolvuldcece. 



Elegant herbaceous plants, generally either trailing or twining, in 

 which latter case their slender string-like stems often reach many 

 yards in length. Leaves simple, alternate, petiolate, usually undivided, 

 often beautifully heart-shaped. Flowers large, axillary, usually soli- 

 tary, regular, formed of five petals united into an exquisite bell, 

 shaped like the mouth of a trumpet, as in Fig. 142, and spirally 

 twisted before expansion ; in colour white, pink, azure, crimson, or 

 purple, sometimes particoloured, or richly striped at the line of 

 jimction of the component petals. Stamens five, on long filaments, 

 inserted in the base of the corolla ; pistil solitary, very long ; stigma 

 two-lobed ; calyx of five sepals, which are often unequal ; fruit a four- 

 seeded capsule. Few flowers are more fugitive ; many kinds open at 

 daybreak or earlier, attain perfection by sunrise, and wither before 

 noon, imless the skv be overcast. 



Fig. J 42. 

 Flower of Convolvulus. 



Fig. 143. 



Leaf of Convolvulus major. 



This beautiful family is abundant in all parts of the tropics, but 

 rare in the colder regions, and at the extreme north entirely unknown. 

 The number of species is between six and seven hundred. The roots 

 abound for the most part with an acrid milky juice, containing a 

 peculiar resin, the action of which is strongly purgative, jalap and 

 scammony being the chief examples. In a few kinds the purgative 

 resin is hardly present, and then the large roots are often remarkable 

 for their sweet and starchy contents, as in the common sweet-potatoe, 

 or "batatas," so important an article of food in tropical countries. 



