THE STEM. 



71 



CHAPTER XV. 



THE STEM, OR ASCENDING AXIS. 



211. The general idea of the Axis is this : the central substan- 

 tial portion of the plant, bearing the appendages, viz., roots 

 below, and the leaf-organs above. The Ascending Axis is that 

 which originates with the plumule, tends upward in its growth, 

 and expands itself to the influence of the air and the light. 



218. Procumbent stem Chiogenes higpldula. 



212. Although the first direction of the stem's growth is ver- 

 tical in all plants, there are many in which this direction does 

 not continue, but changes into the oblique or horizontal, either 

 lust above the surface of the ground, or iust beneath it. If the 

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

 monly 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 ground after having at the base arisen 

 somewhat above it, it is decumbent. If it arise obliquely from a 



249, Decumbent stem Anagallis arvensis. 



prostrate base, it is said to be ascending and if it continue 

 buried beneath the soil, it is subterranean. Such stems, although 

 buried like roots, may readily be known by their buds as already 

 explained ( 210). 



