VIII. THE STEM. I 5 5 



15. By our definition, a stem is a spirally bent, 

 essentially living and growing, shoot of vegetation. 

 But the branch of a tree, in which many such 

 stems have their origin, is not, except in a very 

 subtle and partial way, spiral ; nor except in the 

 shoots that spring from it, progressive forwards ; 

 it only receives increase of thickness at its sides. 

 Much more, what used to be called the trunk of a 

 tree, in which many branches are united, has ceased 

 to be, except in mere tendency and temper, spiral ; 

 and has so far ceased from growing as to be 

 often in a state of decay in its interior, while the 

 external layers are still in serviceable strength. 



16. If, however, a trunk were only to be defined 

 as an arrested stem, or a cluster of arrested stems, 

 we might perhaps refuse, in scientific use, the 

 popular word. But such a definition does not 

 touch the main idea. Branches usually begin to 

 assert themselves at a height above the ground 

 approximately fixed for each species of tree, — low 

 in an oak, high in a stone pine ; but, in both, 

 marked as a point of structural change in the 

 direction of growing force, like the spring of a 

 vault from a pillar ; and as the tree grows old, 

 some of its branches getting torn away by winds 

 or falling under the weight of their own fruit, or 

 load of snow, or by natural decay, there remains 



