246 



WEEDS AXD USEFUL PLAISTTS. 



Order LI. CONYOLYULA'CE^. (Convolvulus Family.) 



Mostly trailing or tioining Jieris, often witi a milky juice ; leaves alternate (in Cuscuta 

 reduced to minute scales) ; flowers regular, hexandrous ; calyx of 5 imbricated persistent 

 sepals; corolla 5-plaited or 5-lobed, twisted or convolute in the bud ; orar!/ 2-celled (rarely 

 3-celled) with a pair of erect ovules in each cell, the cells sometimes doubled by a false 

 partition between the seeds, so becoming 4-celled ; the emhi-yo large, curved or coiled in a 

 mucilaginous aRjwnien. Pria'i a globular 2- 6-seeded pod. 



A family containing many showy plants, some of which are cultivated for ornament. 

 The medicinal products, Jalap and Scammony, are furnished by plants of this order. 



Fig. 157. Common Hounds-tongue (Cynoglossum officinale). 15S. Portion of the corolla 

 with the scales which close the throat.' 159. The fruit, consisting of prickly nutlets adher- 

 ing to the base of the styel. 



