SHADE, LAWN, AND PARK TREES. 339 



Rocky Mountains have more value in landscape work than 

 is usually suspected, especially in the more rugged portions 

 of the grounds. Of its proper position Downing has said: 

 " It is most agreeable to the eye in composition when it 

 forms the undergrowth or thicket, peeping out in all its 

 freshness of gay blossoms or bright fruit from beneath and 

 between groups and masses of trees." 



Pyrus ringo of east Europe also has thick dark-green 

 leaves that are not killed by the first frosts. They often 

 remain green and seemingly unfrozen until December in 

 Iowa. It is a handsome round-topped tree bearing large 

 pure white flowers and full crops of ornamental crab-apples. 

 This is hardy in all parts of the Union. 



324. Poplars and Willows. These rapid-growing trees 

 have value in certain places in parks and on large places. 

 The true white poplar of east Europe makes a large tree 

 with silvery foliage. It does not sprout as much as the 

 gray poplar or abele of west Europe. In the centre of a 

 large group, or at an angle or corner, it gives variety of ex- 

 pression in contrast, as Downing says, with darker- foliaged 

 species. If the sprouts are pulled up as they appear the 

 tendency to sprout does not last long. But if cut off they 

 grow stronger than before. 



The variety Bolleana also sprouts but little. This is 

 upright in habit and is only admissible where trees with 

 silvery foliage and upright habit are wanted to fix atten- 

 tion to a particular point in the landscape. 



Populus certinensis of east Europe has a fine pyramidal 

 habit, with large heart-shaped dark-green leaves with wavy 

 or folded edges. It can be used everywhere to give variety 

 to groups of quick -growing trees. 



The willows also have certain uses. In large cemeteries 

 And near water such weeping varieties as Babylonica, Kil- 



