52 THE TREE BOOK 



which cleverly avoids the hot rays of the sun 

 by pointing its leaves north and south, and train- 

 ing them edgewise to the sky. Longfellow tells 

 us about this in Evangeline: 



" 'Patience,' the priest would say, 'have faith and thy 



prayer will be answered. 

 Look at this delicate plant, that lifts its head from 



the meadow ; 

 See how its leaves all point to the north, as true as 



the magnet. 

 It is the compass-flower, that the finger of God hath 



suspended 

 Here on its fragile stalk, to direct the traveler's 



journey 

 Over the sea-like, pathless, limitless waste of the 



desert. 

 Such in the soul of man is faith.' " 



Many trees protect their leaves with a fine 

 coating of downy hairs. In some cases this 

 coat acts as a sun-screen ; in others it serves as 

 a blanket. The desert willow and the sage 

 brush of the dry plains are clothed all over with 

 short, thick hairs. In the far north, a little 

 coating of soft, furry hairs protects the leaves 

 and twig tips of the hoary willows. 



Nearly all of the leaves we examine have pale 

 under surfaces; indeed some of them, like the 

 poplar, are silvery-gray, shading almost to 



