SOME IMPORTANT FAMILIES OF ANGIOSPERMS 309 



327. The Convolvulus Family. This, as well as all the 

 other families to be mentioned later, is composed of plants 

 whose petals, and generally the sepals as well, are united 

 into tube- or bell-shaped structures. There are usually 

 five sepals, the same number of petals and of stamens, and 

 a single two-parted pistil. Many members of the family 

 are climbing plants. The genus Ipomosa includes the morn- 

 ing-glories, a number of which are in cultivation, and the 

 sweet potato, whose thickened roots we eat. The bindweeds 

 belong to the genus Convolvulus ; some of them are trouble- 

 some weeds. The parasitic dodders were described in 

 Chapter XIV. 



328. The Mint Family. The 3000 species of this family 

 are chiefly herbs with four-sided stems and opposite leaves. 

 Most of them have irregular, two-lipped flowers, with five 

 sepals and five petals, four stamens, two of which are longer 

 than the other two, and a two-parted pistil. The ripe fruit 

 separates into four (occasionally fewer) parts, each containing 

 a single seed. Many species contain aromatic substances 

 that make them valuable for flavoring purposes, or as 

 sources of perfumes and drugs. Well-known useful plants 

 are the peppermint and spearmint, pennyroyal, horehound, 

 rosemary, lavender, sage, balm, savory, and thyme. Coleus 

 is widely raised for ornamental purposes because of its 

 variegated leaves, and some tropical species of Salvia (the 

 sage) are cultivated for their showy flowers. The catnip, the 

 horsemint, and some of the true mints (species of Mentha) 

 are common weeds. 



329. The Nightshade Family. This includes chiefly 

 round-stemmed herbs, whose flowers are usually regular, 

 with five sepals, five petals, five stamens, and a two-parted 

 pistil. The fruit is a many-seeded capsule or berry. The 

 potato and the eggplant are members of the genus Solanum, 

 to which the nightshades and the horse nettle, a troublesome 

 weed, also belong. Tobacco, the tomato, the red peppers, 



