Some Families of Angiosperms 543 



ber 200 genera and 3000 species. They are mostly herbs, with 

 square stems and simple leaves, and with epidermal glands se- 

 creting volatile oils that give the 

 characteristic odors to many of the 

 species. The floral whorls, except 

 the pistil, each consist of five mem- 

 bers. The pistil is composed of 

 two carpels, each of which is two- 



lobed, so that the fruit consists of Fig. 349. Climbing nightshade iSola- 

 four nutlets. The oils of pepper- ««w<^«^cawam), one of the wild species 

 • , • . . 1 1 1 belonging to the potato family. 



mmt, spearmmt, thyme, lavender, 



rosemary, and horehound are of commercial importance in the 



manufacture of flavoring extracts, perfumes, and medicines. 



The potato family (Solanaceae). This group of 75 genera 

 and 1500 tropical and temperate species is best developed in 

 Central and South America. It includes herbs, shrubs, and 

 small trees with petals united into a disk, or forming a tube with 

 flaring end. The fruit is a berry or a capsule. Many of the 

 species are poisonous. The potatoes, tomatoes, and peppers are 

 familiar garden species. Equally important commercially is 

 the tobacco plant. The " deadly nightshade " is the source of 

 the drugs atropine and belladonna. 



The sunflower family (Compositae). This is the largest fam- 

 ily of flowering plants, comprising about 900 genera and more 

 than 13,000 species. Most of the species are herbs, though 

 in the tropics there are a few shrubs and trees. The flowers are 

 usually small, with tubular or strap-shaped corollas. The 

 flowers, however, are grouped in heads, with an outer circle of 

 green bracts so that the flower cluster is frequently mistaken 

 for a single flower. The fruits are achenes, and in many species 

 the fruits have a ring of bristles which lead to their distribu- 

 tion by the wind. In this, the culminating family of the dicoty- 

 ledons, the production of a multitude of seeds is accomplished 

 by the occurrence of many small flowers in heads. This is in 



