366 



BOTANY AND PHARMACOGNOSY. 



Convolvulus Scammonia is a perennial twining herb, with a 

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

 the ofificial scammony (p. 656). The leaves are sagittate; the 

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

 morning-glory, and occur in the axils of the leaves, either solitary 

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



Fig. 174. 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. 



A number of the plants of the Convolvulacese are cultivated, 

 probably the most important of which is the sweet potato vine 

 (Ipoiiia-a 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 

 in sub-tropical countries. The starch is a commercial product 

 and is kiwwn as sweet-potato starch or Brazilian arrow-root. 



