LECT. VI.] THE STEM. ITS DIRECTION. 241 



LECTURE VI. 



THE STEM ITS DIRECTION DIVISIONS AND BRANCH- 

 ING COVERING COLOUR FIGURE. CLASSIFICA- 

 TION OF STEMS. 



HAVING finished the consideration of the root, 

 I have now to direct your attention to the two 

 next divisions, in our enumeration of the parts of 

 the plant, the stem and the branches. These or- 

 gans are generally above the surface of the ground, 

 and consequently in sight : I therefore propose, in 

 order to methodize our investigation, to view them 

 in the first place, simply as they are presented 

 to the eye, in the entire plant ; then more closely 

 as regards those external properties on which Bo- 

 tanists have founded their classifications of them ; 

 and lastly, to demonstrate the anatomy of their 

 internal structure : thus preparing you to under- 

 stand more readily their physiology. You should, 

 however, be previously informed, that the stem and 

 branches are organs not essential to the vegetable 

 structure, although they are so to the plants in 

 which they are found ; for, independent of some 

 Lichens, and many species belonging to those 

 tribes of vegetables which Botanists have deno- 

 minated imperfect, they are never present in many 

 VOL. i. R 



