CHAPTER XVII 



SOLANACEAE 



SOLANUM TUBEROSUM 



THE nightshade family, Solanaceae, contains many important 

 vegetable crops including: potato, Solanum tuberosum L.; 

 eggplant, S. Melongena L.; tobacco, Nicotiana Tabacum L.; 

 tomato, Lycopersicum esculentum Mill., and several varieties of 

 pepper belonging to the genus Capsicum. In addition, some mem- 

 bers of the family are grown as ornamentals, and a number of 

 them produce alkaloids that are used as drugs. 



The potato plant is a native of the highlands of South and Central 

 America, and a wild tuber-pVoducing form, Solanum Jamesii, is 

 still found in the mountains of Arizona, Colorado, Texas, Utah, 

 and Mexico. The wild species resemble the cultivated Solanum 

 tuberosum, except that the latter has a larger vine and a more 

 pronounced development of tubers. Berthault (4) regards Sola- 

 num tuberosum as a distinct species which has not been derived 

 from native ones by selection or mutation, and points out that it 

 differs from the wild tuberous forms in its floral organization, 

 especially with respect to its rotate corolla and the sharp-pointed, 

 mucronate, calyx lobes. 



GENERAL MORPHOLOGY 



The potato is an annual, herbaceous dicotyledon as far as its 

 vegetative and flowering habits are concerned, but it may be 

 regarded as a potential perennial owing to its capacity for vegeta- 

 tive reproduction by means of tubers. These arise on underground 

 stems and from them new shoots are produced. 



The Stem. — The aerial stem is herbaceous and erect in its early 

 development, but later may become spreading and semi-prostrate. 

 It reaches a height of i to 5 feet or more; and, after becoming pro- 

 cumbent, may produce several axillary branches. The stems are 

 green or purplish, and are round to subtriangular or quadrangular 



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