SEED-BEARING PLANTS 



479 



421. Mint Family (Labiatae).— The Mint family is 

 characterized by a square stem, opposite leaves, a tubular 

 calyx, caused by the coalescence of the five sepals, a highly 

 modified corolla having two lips or labia (singular labium, 

 whence the family name), and leaves containing many 



Fig. 363. — Bindweed {Convolvulus arvensis). 



small glands that secrete a volatile oil, which gives the char- 

 acteristic odor and taste to all the plants of the family. 

 The upper lip results from the fusion of two petals, the 

 lower lip by the fusion of three. Everyone is familiar 

 with one or more of these features, as embodied in the 

 various mints, pennyroyal, horehound, catnip, sage, 

 savory, thyme, hyssop, wild marjoram, and other condi- 



