688 A TEXT-BOOK OF BOTANY. 



America, where they are extensively cultivated, as also in Africa 

 and India. 



Nicotiana Tabacum (Virginia Tobacco plant) is a tall annual 

 herb indigenous to tropical America and widely cultivated. The 

 stem is simple, giving rise to large, pubescent, ovate, entire, decur- 

 rent leaves, the veins of which are prominent and more or less 

 hairy. The flowers are long, tubular, pink or reddish, and occur in 

 terminal spreading cymes. The various forms of tobacco are 

 made from the leaves, which are hung in barns, whereby they 

 undergo a slow drying or process of curing. Other species of 

 Nicotiana are also cultivated, as N. persica, which yields Persian 

 tobacco ; and N. rustica, the source of Turkey tobacco. Tobacco 

 leaves contain from 0.6 to 9 per cent, of the alkaloid nicotine ; an 

 aromatic principle nicotianin or tobacco camphor, to. which the 

 characteristic flavor is due and which is formed during the curing 

 of the leaves. The dried leaves yield from 14 to 15 per cent, of 

 ash, consisting in large part of potassium nitrate. 



Solanuvn tuberosum (Potato plant) is indigenous to the Andes 

 region of South America and is extensively cultivated on account 

 of the edible tubers. The tubers (potatoes) contain about 75 per 

 cent, of water, 20 per cent, of starch, and nearly 2 per cent, of 

 proteins in the form of large protein crystalloids. The fruits and 

 young shoots contain the gluco-alkaloid solanine and the alkaloid 

 solanidine. The tubers contain a small amount of solanine, which 

 is increased when they are attacked by certain fungi or exposed 

 to light. (Consult pp. 142, 148, 194, and 198.) 



Besides the potato plant, several other plants belonging to the 

 Solanaceae yield vegetables, as the Tomato plant (Solanuin Lyco- 

 persicum) and the Egg plant (Solanum Melongena). Various 

 cultivated species of Capsicum annuum furnish the common red 

 peppers of the market. 



g. SCROPHULARIACE^ OR FIGWORT FAMILY. 

 The plants are herbs, shrubs or trees with opposite or alternate 

 leaves and perfect, mostly complete and irregular flowers. The 

 corolla and stamens show some resemblance to those of the Labi- 

 atse in that the corolla is frequently more or less 2-lipped and the 

 stamens are didynamous. The fruit is a dehiscent capsule and 



