THE POPLAR FAMILY. 



373 



remarkable for having their long and slender petioles flattened at a 

 right angle with the blade or lamina, the consequence of which is that 

 the wind in playing among the leaves is always met by a broad surface, 

 and hence the pi'etty and incessant quivering which has made a pro- 

 verb of the aspen, in which species the movement is incessant. The 

 catkins, both male and female, are in almost all cases " dioecious," or 

 upon separate individuals ; they are usually large and handsome, and in 

 spring contribute greatly to the ornament of the groves and hedge- 

 rows. In many instances they do not appear till after the leaves are 

 open. 



Fig. 101. 

 Willow — Female catkins. 



Fig. 192. 

 Willow — Male catkins. 



Both the poplars and the willows are valuable, either as timber- 

 trees, or for miscellaneous economic purposes. The use of osiers for 

 basket-making, and of sallow- wood for the manufacture of charcoal, is 

 well known. They are natives of much the same districts as the 

 members of the oak and birch families, namely, of the temperate parts 

 of the northern hemisphere, and extend even further towards the pole. 

 The most northern woody plants known are the two little willows 

 called Salix arctica and Salix poldris. The Salix herbacea, which is 

 another arctic species, creeps southwards as far as our own country. 

 (Figured in E. B. xsvii. 1907.) A very considerable number of 



