Trees; their General Character and Advantages. 343 



graceful appearance to the common American elm and the 

 Aveeping willow. Others exhibit less waving of the branch- 

 es ; but when the wind passes through them their foliage is 

 put into rapid motion, making an agreeable rustling sound as 

 if the tree Avas full of life. This trembling of the leaves is 

 proverbial in the aspen, and in many other poplars; and it 

 distinguishes the pear tree from the apple tree, and the com- 

 mon white birch from its kindred species. The leaves of 

 most trees, whose foliage is remarkably tremulous, are heart- 

 shaped and smooth on their upper surface, like those of some 

 of the evergreens. 



Besides these natural dissimilarities in the forms and habits 

 of trees, there are others which may be termed accidental. 

 In a forest the trees are so closely set as to lose much of their 

 individual peculiarity, growing up to a great height and pre- 

 vented from spreading out their lower branches by the close 

 vicinity of other trees. Hence writers have made this dis- 

 tinction between a forest and a grove. In the latter the 

 trees are sufficiently far apart to admit of their full develop- 

 ment ; in a forest they are so thickly planted as to run. up 

 like great pillars, their branches making an even canopy of 

 foliage above our heads. A grove, therefore, approaches 

 more nearly to a state of cultivation than a forest, in which 

 we seldom find a perfect tree. 



The public, at the present day, is very generally convinced 

 of the importance of planting trees by the roadsides and 

 around their enclosures. Not only do they aff'ord us shade 

 and shelter, but they tend to equalize the temperature of the 

 atmosphere at all seasons. It is well known to travellers that 

 the forests are cooler in summer and warmer in winter than 

 the open plains, and that the equability of the climate would 

 be improved in proportion as the whole continent should be 

 covered with trees. And how many barren roadsides, where 

 one is scorched with the fervid heat of the summer at one 

 season and chilled with the bleak wintry winds at another, 

 might be bordered with millions of beautiful trees, to yield 

 comfort and protection both to the traveller and the dweller 

 in their vicinity. 



