1902 



A TEXTBOOK OF THEORETICAL BOTANY 



In certain genera, e.g., Datura, Scopolia and Atropa, there is no intraxylary 

 phloem in the roots. 



The leaves of the Solanaceae are usually alternate on the vegetative 

 branches but become opposite in the flowering shoots. Both the branching 

 and the leaf arrangement are, however, subject to many irregularities pro- 

 duced by adhesion, that is the adnation of leaves and shoots to the main 

 axis, in varying degrees. Thus, leaves are frequently adnate to the whole 

 of the internode above, so that they appear at the node above their point of 

 origin, while in Solatium nigrum, and other species, the inflorescence 

 peduncle is partly adnate to the axis and appears to be attached to the middle 

 of an internode. 



The family is of considerable economic importance. We have already 

 referred to a number which are used as vegetables. Others yield drugs, as 

 for example Atropa (Fig. 1821), Hyoscyamus, Solatium and Datura. Many 



Fig. 1 82 1. — Atropa helladonmi. Deadly Nightshade. 



are cultivated in gardens as semi-hardy perennials or as annuals. Among 

 the best known are Petunia, Nicotiatia, Salpiglossis, Schizatithus and 

 Datura. 



According to Wettstein the family is classified as follows, the chief 

 characters being the shape of the embryo and the nature of the gynoecium. 



I. Solanoideae 



Embryo curved through more than a semi-circle. All five stamens 

 fertile and equal or only slightly unequal. 



1. Nicatidreae. Ovary three- or four-chambered, the walls of the 



loculi dividing the placentae unequally. Nicatidra, a native of 

 Peru, but cultivated widely as a garden plant. 



2. Solatieae. Ovary two-chambered. This tribe contains the largest 



number of the genera and is sometimes further subdivided. 



