288 



CONSERVATIVE ORGANS. 



[LECT. vn. 



tions or diaphragms (fig. a, 

 1) ; or the stem is knotted, 

 and apparently made up 

 of separate hollow por- 

 tions, shut at each ex- 

 tremity, and united at the 

 knots. The different spe- 

 cies of Horse-tail, Equi- 

 setum ; Manured Reed 

 Arundo donax; Common Water Drop wort, 

 CEnathe Jistulosa ; the Castor oil plant, Ri- 

 cinus officinalis ; and almost all the Grasses, 

 and the Cerealia, afford examples of this 

 variety (fig. a, 2). 



Such is the diversity of substance of sterns 

 and branches ; we have now to examine the ana- 

 tomical construction of these organs. To the stu- 

 dent, this inquiry is not only important, as dis- 

 playing the structure of the stem itself, and 

 thereby enabling him to comprehend more per- 

 fectly its- functions and mode of growth ; but, as 

 all the parts concerned in the vegetable functions, 

 as far as the preservation of the individual is con- 

 cerned, are seen in the stem ; by a correct know- 

 ledge of its organization he becomes acquainted 

 with that also of the root, the leaves, and even, 

 in some respects, of the flowers and the fruit. In 

 this investigation it is essential to adopt some ar- 

 rangement; and although none, which has yet 

 been attempted, is free from just causes of cri- 



