120 FAMILIAR TREES 



It lias been observed that winter thunderstorms 

 are more destructive to trees than those in 

 summer ; that Oaks overgrown with Ivy are seldom 

 struck ; and that perhaps trees with rounded leaves 

 are more liable to injury from this cause than 

 those whose leaves are pointed. The leaves, it is 

 suggested, act as a myriad of discharging points 

 for the atmospheric electricity ; in which case, of 

 course, evergreens would have a decided advantage. 

 When, however, we consider the landscape effect 

 of an exclusively evergreen tree-flora, it must be 

 admitted that the uniform dark tints of its peren- 

 nial verdure are apt to pall upon the senses. 

 Evergreen leaves are almost invariably thicker than 

 those of deciduous plants, and besides having 

 occasionally an epidermis of more than the usual 

 single layer of colourless cells, they have com- 

 monly a " hypoderm," or sub-epidermal tissue, also 

 consisting of more than the usual number of 

 layers of cells, which being, as they are, in a 

 vertical position, and filled with " chlorophyll," or 

 " leaf-green," give the leaf its characteristically 

 dark tint, absorbing far more light than the 

 transparently thin and pale-hued foliage of our 

 northern forests. Beneath the gloom of the Hex 

 "it is always afternoon," and the heart of the 

 traveller turns to the restful green of northern 

 pastures, and even to the bare boughs of winter 

 that tell of Nature's rest. 



