62 



ORGANOGRAPHY. 



BOOK I. 



the air. While this ascending tendency is by many plants 

 maintained during the whole period of their existence, by 

 others it is departed from at an early age, and a horizontal 

 course is taken instead; while also free communication with 

 liofht and air is essential to most stems, others remain durins 

 all their lives buried inider ground, and shun rather than seek 

 the light. From these and other causes, the stems of plants 

 assume a number of different states, to which botanists attach 

 particular terms. It will be most convenient to divide the 

 subject into the varieties of — 



1. T^he subterraneaJi stem ; and, 



2. The aerial stem. 



The SUBTERRANEAN Stem, often called souche by the French, 

 was confounded by all the older botanists, as it still is by the 

 vulgar, with the root, to which it bears an external resem- 

 blance, but from which it is positively distinguished both 

 by its ascending origin, and by its anatomical structure. 

 {See Root.) 



23 



24 







Bir 



The following are the varieties which have been distin- 

 guished : — 



Tlie Cormus^ fig. 23. {Lecus of Du Petit Thenars, Plateau 

 of De Candolle), is the dilated base of the stem of Monocoty- 

 ledonous plants, intervening between the roots and the first 

 buds; and forming the reproductive portion of the stem of 



