THE NIGHTSHADE FAMILY. 239 



XXXVII. THE NIGHTSHADE FAMILY. 

 SOIiANACE^;. 



MATERIAL REQUIRED. 



The cultivated potato in flower. The tomato may be substituted. 



Specimens of matrimony-vine, Lycium vulgare, Dunal, in flower, and 

 similar specimens of ground-cherry, Physalis pubescens, L., bitter- 

 sweet, Solanum Dulcamara, L., or other easily procurable repre- 

 sentatives of the family. 



POTATO. Solanum tuberosum, 

 Distribution and General Characters. 



The common potato is indigenous to a portion of the 

 coast region of western South America. It has been 

 widely cultivated in the northern hemisphere for more 

 than three hundred years, apparently with little specific 

 change, there having been no inducement to artificial 

 selection of any other part than the tuber, which, however, 

 presents many, often striking, varieties.^ 



In examining the cultivated plant, study its habit, not- 

 ing the peculiarities of stem and leaves, and the character- 

 istic odor. 



Inflorescence. 



Examine a number of specimens. Do they agree in the 

 character of the inflorescence? Describe this and draw a 

 diagram showing the position of the flowers and their 

 order of development. 



1 Cf. De CandoUe, Origin of Cultivated Plants, p. 45 et seq. 



