THE CULTIVATED POPLARS. 211 



ing for the catkins which are produced so freely in early spring. 

 The European aspen (Populus Tremula) is particularly desirable in 

 this respect (Fig. 13); and this species also has a most interesting 

 habit and foliage. 



It should be said, in passing, that most of the poplars are 

 hardy trees and thrive in a great variety of trying situations. 

 This, together with the ease of propagation and their cheapness, 

 combined with free and rapid growth, makes them the best of 

 trees for nurse plantations, that is, for temporary shelter for 

 other trees and bushes. In this respect the common aspen poplar 

 is one of the most valuable of all trees in the reforestation of 

 American lands. It springs up quickly in clearings, and during 

 its comparatively short life holds the soil and protects other vege- 

 tation and finally contributes its own substance to the mainten- 

 ance of the stronger forests. In this manner it has exerted a 

 most powerful effect upon the configuration of our forest areas 

 and upon the fertility of the land from remote time. The same 

 qualities make it valuable, in many instances, in extensive 

 ornamental plantings. 



The recent introduction of Russian poplars has added consid- 

 erable confusion to nursery lists, and it was this fact which first 

 led me to take up this inquiry. The chief merit of the Russian trees 

 is for planting in the northwestern prairie states, but all of them 

 are worth attention for exposed localities in this state, as well as 

 for ornamental planting. I am convinced that the so-called 

 Populus Certinensis (properly P. laurifolia) is one of the very best 

 trees to plant where quick results are wanted and where some 

 feeling of strength and durability is also desired. The best dis- 

 cussion of these Russian poplars which I know is contained in 

 Bulletin No. 9 of the Minnesota Experiment Station by Professor 

 S. B. Green, published in 1889. The following is a more recent 

 sketch of these trees by the same author, prepared for this occa- 

 sion : 



"Russian Poplars in the Northwest. In the arboretum of the 

 Minnesota Experiment Station are 1 2 kinds of Russian poplars 

 that were received from the Iowa Agricultural College. Most of 

 them have been grown in our collection for seven years, and some 

 of them have been tried for a much longer period in other parts 



