200 Choice of Plant Material 



protection which may enable a specimen of a half-hardy 

 species to endure adverse cHmatic conditions. And, finally, 

 there is such a thing as individual hardiness, a given speci- 

 men enduring what the species in general may not be ex- 

 pected to survive. 



Again, local variation of climatic conditions, due to aspect 

 and protection against winds, is quite remarkable. Thus 

 the north or the south slope, the top of a hill or a depression, 

 often produces sufficient difference to enable a species to 

 thrive in the one and not in the other limited locality, 

 although the two may be only a few hundred yards apart. 



We may not, therefore, draw valid conclusions from single 

 observations, and the word "hardy" may only be under- 

 stood in general terms. 



For determination of the likelihood of hardiness, we have 

 referred to a publication of the Canadian Experiment 

 Farms, by Dr. \\'m. Saunders, in which are given the results 

 of long-continued tests of a very extensive list of trees and 

 shrubs in the untoward climate of Ottawa, Manitoba, and 

 the Northwestern Territories.^ 



Besides the two paramount considerations of climatic and 

 soil-adaptation, the following points will enter into the 

 selection of plant material. 



1. Ornamental value; which depends upon outHne, habit 

 of growth, and final form of crown, as well as upon character, 

 shape, arrangement, and color of foliage and bark, the 

 autumnal tints to which it changes, and, although in a minor 

 degree in trees, on flowers, fruit, and bark. 



2. Shading value; which depends not only on the size, 

 form, and density of the foliage, but also on leaf period, i.e., 

 the earlier or later leafing-out and the earlier or later fall 

 of foliage. 



1 Bulletin No. 47, 1904. 



