THE ROMANCE OF OUR TREES 



and branches toward light is identical with the 

 primary ones but toward gravity it is about inter- 

 mediate for usually they grow more or less horizon- 

 tally away from the central axis. In the case of the 

 roots to ensure a broad field from which to draw 

 water and food salts ; in the case of the shoots to give a 

 wide field for the leaves to intercept light and air 

 the more completely to perform their allotted work 

 in the tree's economy. In the Lombardy Poplar all 

 the secondary and tertiary branches grow erect after 

 the manner of the primary shoot; in the Weeping 

 Willow the tertiary branches simulate the behaviour 

 of primary roots in that they grow downward toward 

 the earth's centre. Of the remarkable and opposite 

 behaviour of the branches of these two trees the 

 most casual observer is cognizant, but the why of 

 this phenomenon is a poser to those most deeply 

 versed in tree-lore. The secret has not yet been 

 wrested from the living substance scientists designate 

 as protoplasm. But if it is beyond the wit of man to 

 explain the cause. Garden-lovers, from early times, 

 have not been backward in appreciating the value of 

 such strikingly distinct forms of tree-growth for 

 garden embellishment. 



Among such Conifers of the Northern Hemisphere 

 as Juniper, Thuja, Chamaecyparis, and Cypress 

 many species are columnar in outline. In some, 



242 



