THE STEM, OR ASCENDING AXIS. 31 



stem continues to arise in the original direction, as it most commonly 

 does, it is said to be erect. If it grow along the ground without rooting 

 it is said to be procumbent, prostrate, trailing. If it recline upon the 

 oround after having at the base arisen somewhat above it, it is decum- 

 bent. If it arise obliquely from a prostrate base, it is said to be ascend- 

 ing, and if it continue buried beneath the soil, it is subterranean. 



39. Decumbent stem Anagallis arvensia. 



149. SUBTERRANEAN STEMS may be readily distinguished from the 

 roots by the natural and habitual presence of buds in the former, regu- 

 larly arranged, while no buds (unless rarely adventitious) exist in the 

 latter. 



150. STEMS ARE EITHER SIMPLE OR BRANCHED. The simple stem is 

 produced by the unfolding of the primary bud (the plumule) in the di- 

 rection of its point alone. As this bud is developed below into the 

 lengthening stem, it is continually reproduced at its summit, and so is 

 always borne at the termination of the stem. Hence the axis is always 

 terminated by a bud. 



151. THE BRANCHED STEM, which is by far the most common, is pro- 

 duced by the development of both terminal and axillary buds. The 

 axis produces a bud in the axil of its every leaf, that is at a point just 

 above the origin of the leaf-stalk. These buds remain inactive in the 

 case of the simple stem, as the mullein, but more generally are devel- 

 oped into leafy subdivisions of the axis, and the stem thus becomes 

 branched. 



152. A BRANCH is, therefore, a division of the axis produced by the 

 development of an axillary bud. This bud, also, ever renewed, is borno 

 at the termination of the branch, so that axillary buds each in turn be- 

 come terminal. 



153. THE ARRANGEMENT OF THE BRANCHES upon the stem depends 

 therefore upon the arrangement of the leaves, which will be more par- 

 ticularly noticed hereafter. This arrangement is beautifully regular, 

 according to established laws. In this place we briefly notice three 

 general modes : 



The alternate, where but one branch arises from the node on differ- 

 ent sides of the stem, as in the elm. 



