CHAPTER XIV 

 TREES OF UPRIGHT HABIT 



THE Lombardy Poplar and the Weeping Willow 

 dealt with in the preceding chapter represent 

 two extreme types and the most diverse varia- 

 tions from the normal habit of tree-forms. Though 

 the oldest authentically known deciduous-leaved 

 trees of their class they are by no means unique ex- 

 amples and, since trees of their remarkable shapes 

 have a considerable field of usefulness in park and 

 garden decoration, it may be useful to enlarge upon 

 the subject. If it be asked why Nature should in- 

 dulge in the development of such abnormal types no 

 answer is forthcoming. The manner in which the 

 peculiar branching habit takes place can be explained, 

 but what induces it and the reason why are mys- 

 teries. Light and gravity exercise diametrically op- 

 posite effects on the primary root and primary shoot 

 of a tree. The root grows away from light and 

 toward the centre of the earth; the shoot contrari- 

 wise grows toward light and away from the earth. 

 The behaviour of secondary and tertiary roots 

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