CLASSIFICATION OF ANGIOSPERMS. 



669 



plants produce slender rhizomes with tuber-like roots, these being 

 used in medicine. 



Convolvulus Scammonia is a perennial twining herb, with a 

 large tap root, containing a resinous latex, and is the source of 

 the official scammony root. The leaves are sagittate ; the flowers 

 are large, yellowish- white and funnel- form, as in the morning- 



FIG. 366. Great bind weed (Convolvulus sepium) showing trailing or twining habit, 

 the hastate leaves and funnel-shaped corolla. The plant is very resistant to noxious fumes 

 and is usually found in smelter regions. 



glory, and occur in the axils of the leaves, either solitary or in 

 clusters. The fruit is a 4-seeded, 4-locular, dehiscent capsule. 



A number of the plants of the Convolvulaceae are cultivated, 

 probably the most important of which is the SWEET POTATO vine 

 (Ipomoca Batatas}, a plant extensively cultivated in tropical and 

 sub-tropical countries on account of the edible tuberous roots. 

 The roots contain from 3 to 10 per cent, of sugar and 9 to 15 per 

 cent, of starch, which occurs in larger proportion in plants grown 



