CHAPTER XV. 



TREES AND SHRUBS. 



374. Trees and Shrubs. There is no sharp distinction 

 between herbaceous and arboreous plants, though the terms 

 herb, shrub, and tree are convenient for general use. It is 

 perhaps sufficient to define a tree or shrub as a woody plant 

 whose stem persists above the soil year after year as com- 

 pared with a plant which dies down to the level of the soil, 

 though the " root- stock " or rhizome is hard and woody. 



A tree usually possesses a stout, main trunk from which 

 smaller and more slender lateral branches arise. Frequently, 

 however, the main stem is short, and is exceeded in length 

 by the branches. A shrub, on the other hand, is simply a 

 miniature tree, the stem being usually short, and soon breaking 

 up into numerous more or less erect branches. 



Various plants which form large trees when growing in 

 sheltered or low-lying places are reduced to stunted shrubs 

 when they occur on high mountains or wind-swept ridges. 

 On Dartmoor, for instance, there are several patches of 

 gnarled and stunted oak trees, doubtless of great age, grow- 

 ing among granite boulders along river valleys, at a height of 

 about 1,500 ft. On several of the "tors" (granite-caps on 

 hills) there grow Rowan (Mountain Ash) plants reduced to 

 low creeping shrubs a few inches high ; in one case the flat 

 top of a tor, about 1,800 feet above sea-level, was covered 

 with this dwarf Rowan. 



375. Hints on Tree Study. In studying trees, the 

 following points should be specially attended to, full notes 

 and sketches being made in each case : 



(1) The general form and appearance as determined by 

 the mode of branching, the direction of the main branches 

 and finer twigs, and the character of the foliage. 



382 



