184 LEAVES FROM THE BOOK OF NATURE. 



brief noonday time, like gigantic snow-crystals, and cause 

 a chilly shudder. Tn Australia, where all extremes meet, 

 from the bird-fashioned quadruped to the millionaire con- 

 vict, the leaves of trees and bushes have a leathery look 

 and are oddly twisted, turning their edges up and down, 

 instead of standing horizontally, as with us. They afford 

 no shade, and are covered with a white, resinous powder, 

 which gives them a most dismal and pallid appearance. 

 Yet whatever form leaves may assume their wonderful 

 adaptation to their great duty strikes us in all plants alike. 

 The immense extent of surface which they present to light 

 and heat, the thinness and delicacy of their structure, the 

 microscopic beauty of their minute apertures, their power 

 of breathing in and out all answer admirably the great 

 purpose of exposing the crude sap, that rises from the 

 root, to the air and the sun, to be by them digested into 

 highly nutritious food. 



All leaves change their color in autumn, when a pecu- 

 liar chemical change goes on in their substance, and takes 

 the bright, fresh green from them, to leave them in sad- 

 colored livery, or to clothe them, as a parting gift, in 

 the brilliant drapery of an Indian summer. It is then 

 that, especially in American woods, a combination of hues 

 is produced, which no painter can hope to imitate, when 

 the maple burns itself away, and "all the leaves sparkle 

 in dazzling splendor with downy gold colors dipped in 

 heaven." Not less variety may be perceived in the shape 

 of leaves. Needle-shaped in northern evergreens, they are 

 gathered, like tiny brushes, to collect at every point what- 

 ever heat and moisture may surround them. Plants 



