114 ARTIFICIAL ADAPTATIONS OF 



high rural tastes of the jDeoj^le continue to produce their greatest 

 variety and perfection. With us they are never likely to be used 

 to so great an extent for fences owing to the cost of maintaining 

 them ; but as ornamental and useful screens, and for other deco- 

 rative purposes, there need be no limit to their variety. For these 

 purposes some of the evergreens are best. 



The arbor-vitiES are peculiarly adapted for hedges and screens ; 

 especially for those of medium height, which are not intended to 

 turn animals. The species and varieties of arbor-vitai are numer- 

 ous, but it is doubtful if there is one among them all more valuable 

 for this purpose than the indigenous American species which is 

 found wild on the banks of the Hudson, and other eastern rivers ; 

 though it is claimed for the Siberian arbor-vita, and with truth, that 

 its foliage has a richer shade of green. 



There is a material difference in the value of different 



Fig. zi. 



forms for hedges ; and the kind of tree used, the purpose 

 ^ for which the hedge is intended, and the exposure it is to 

 have, must influence the choice of one form rather than 

 another. 



Fig. 2 2 represents a hedge-plant of the arbor-vita; as 

 grown, say the third year after planting. It must now 

 be decided what form the hedge is to have. Fig. 23 is a section 

 of the most common, and, for the arbor-vitae and hemlock, in open 

 exposures, a good form. But it is evi- 

 ^^' dent that a hedge of this form gets F'c- ^4- 



less sun at the bottom than near the ^^*55^ 



top, and the natural result is to pro- ': \ 



duce the weakest growth at the ,,*.v ;-u.--:| 

 bottom, and finally that the lowest IL^^S. 

 branches die out. The shaded parts 

 of hemlocks, if contiguous to moisture, do not seem to suffer for 

 want of the direct rays of the sun, but a majority of hedge- 

 plants need a full and even light upon them. It is not merely the 

 direct rays of the sun which are essential, but that constant light 

 from the sky which, with or without the sun, always rests upon 

 the top of a hedge. If the top be broad as in Fig. 24, it 

 receives nearly all the direct light from above, and shades the 



