THE WILLOWS AND POPLARS 89 



or abele {Populus alba), a large tree of the central and southern 

 parts of that continent. The black poplar is also a large tree of 

 central and southern Europe and Asia. An aspen (Populus trem- 

 iila) occurs in central and northern Europe, ranging eastward to 

 Japan, and there are a number of additional European species, 

 including the downy poplar {Populus canescens); Populus monilifera, ' 

 which furnished the poplar wood of the Romans ; and the so-called 

 Lombardy poplar (Populus fastigiata) so often planted in this 

 country as a screen or ornamental tree. The last is probably of 

 oriental origin despite its name, coming originally from the region 

 of the Vale of Kashmir, since it seems to have been unknown in 

 Italy in Pliny's time. It was unknown in England in Evelyn's 

 day and was introduced into that country about the middle of 

 the 1 8th century. Populus euphratica of North Africa, the Altai and 

 Himalayan region is believed to have been the weeping willow of 

 the Scriptures and its wood along with that of the date palm 

 furnished the rafters for the buildings of Nineveh. The bud gum 

 of the European black poplar and of our American balsam poplar 

 has often been employed by herbahsts for various medicinal pur- 

 poses although it has httle virtue. 



There are in all about twenty-five existing species of poplar, of 

 which half are found in North America. Among these the ones 

 known as aspens have an especially wide range, particularly the 

 quaking aspen, Populus tremuloides, which covers 112° of longi- 

 tude and 41° of latitude, while the European aspen (Populus trem- 

 ula) covers 140° of longitude and 35° of latitude — the two together 

 nearly encirchng the globe. They form dense growths in the north 

 woods and furnish most of the drift wood of the Arctic Ocean. 

 Although cut in vast quantities for pulpwood the aspens will 

 probably always form an important element in the more northern 

 forests as they and their ancestors have done during the past three 

 or four miUion years. They repeat the usual poplar characters of 

 smooth bark, soft weak wood, very rapid growth and sparse broad 

 leafed foliage. They are more gregarious and somewhat smaller 

 at maturity than the other poplars and their long slender leaf 

 stalks cause the hghtest summer breeze to set the leaves to quaking 



