CLASSES OF PLANTS 



443 



3. Morning-glory family. Sweet potatoes and yams are the most use- 

 ful plants in this group and are likely to be used in increasing quantities. 



4. Mint family. All the plants in this family contain more or less 

 aromatic oil, and some of them are accordingly used as a source of 

 flavoring material. The most familiar are sage, thyme, peppermint, and 

 spearmint. A number are cultivated in gardens for their showy flowers. 



5. Potato family. At 

 present the tuber of 

 the white potato is al- 

 most universally used as 

 a source of starch in the 

 diet. The fruit of the 

 tomato plant, which we 

 ordinarily speak of as 

 a vegetable because it is 

 not sweet, is also a very 

 valuable part of the 

 diet, and even when 

 canned may serve as a 

 source of vitamin C 

 where fresh fruit and 

 vegetables are not eas- 

 ily obtained. The red 

 pepper and the egg- 

 plant also belong to 

 this family. Besides 

 food, we get from this 



Fig. 183. The potato {Solaniim tuberosum) 



This plant is a native of America, but has become 

 widely cultivated as a staple source of starchy 

 food. The tuber is an underground stem, the " eyes " 

 being buds. In modern times greatly improved 

 varieties have been developed; Luther Burbank 

 was one of the leaders in this work 



family tobacco and the 



valuable drug belladonna. One of the most dangerous of com- 

 mon weeds is the very attractive thorn-apple, or Jimson weed 

 ('^Jamestown" weed), which is poisonous in all its parts, con- 

 taining the alkaloid stramonium. 



6. Madder family. The coffee bean at the grocery and quinine at the 

 drug store are the most important products of this family. The dye 

 madder was formerly of great importance in producing reds, but is being 

 gradually replaced by coal-tar dyes. 



