THE BIRCH. 371 



become evident at the tip of the short newly-formed branch. They 

 are similar in shape to the staminate catkins, but are always smaller 

 (about half inch long). The scales in their case are three-lobed, and 

 beneath each scale are three female flowers, which consist of an ovary 

 with stigmas. After fertilization these catkins grow rapidly, becoming 

 an inch long and a quarter of an inch or more broad. By the end of 

 the summer the fruits are ripe and the catkins begin to break up, the 

 scales and fruits falling away from the axis, which is left bare. Each 

 fruit is small and flattened in form, and is furnished with a pair of 

 membranous wings to facilitate its dispersal by the wind. 



THE BIRCH (Betula Alba) . 



The Birch is able to endure considerable heat and a greater 

 extremity of cold than any other tree, for it is found farthest north, 

 at a latitude of yo° . We are told that it is the only species of 

 tree in Greenland, and a common inhabitant of Russia and Siberia. In 

 the more northern climates, however, it becomes dwarfed to a mere bush. 



It is a fast -growing tree, and reaches its full height of from 

 forty to fifty feet in as many years. The roots take firm hold upon 

 the soil, and have great powers of penetration. 



Occasionally one may see a young tree growing from the top of 

 a crag ; its roots encircle the stone and draw their nourishment from 

 the earth beneath it ; or again the rock itself is sometimes split by 

 the growth of the roots which have thrust themselves into its 

 crevices. The branches can withstand high wind, for they offer little 

 resistance (owing to their thin foliage and small leaf-surface), but 

 yield and sway with the force of its attack. 



The Birch grows best in light loam, but thrives even on a poor soil. 



Its Usks. The Bark is more enduring than the timber, and it is 

 used for tanning Russia leather. In Lapland houses are roofed with it. 



