TREES 363 



would cause the death of the tree. So it is a good, though 

 to us rather pathetic, thing that the leaves fall. Leaf fall 

 is preceded by the formation of a corky, waterproof layer 

 of cells at the base of the leaf-stalk. In due time the leaf 

 falls off. It is not simply torn off by the wind. The corky 

 layer referred to serves to sever the leaf from the tree. Some 

 trees, hke the maples and boxelder, shed their leaves early; 

 others, like the white oak, retain them sometimes even 

 till spring. Conifers as a class do not shed their leaves all 

 at once. They do, however, lose their needles, which are 

 falling more or less all the time as they mature, or are shaded 

 too much by the younger growth. But since they retain 

 most of their leaves green through the winter we call them 

 evergreens. The tamarack, a conifer, however, sheds its 

 leaves in the fall. In the warmer regions of the earth trees 

 other than conifers retain their leaves in winter, and only 

 shed them gradually like the conifers. The live oak of the 

 southern states is an evergreen, but its northern relatives 

 must shed their foliage in the fall. 



Trees are flowering plants. This is very evident to all in 

 the case of the apple, plum, hawthorn, locust, and other 

 showily flowered trees. Yet the elm, oak, willow, and bass- 

 wood, the cedar, and the pine, all have flowers. Though 

 minute and inconspicuous, they are still very interesting 

 when closely studied, and often very beautiful. Some tree- 

 flowers were described on page 331. 



There is a great diversity in the ways in which trees dis- 

 seminate their fruits or seeds. Some fruit is edible, and 

 animals thus scatter the seed. Some of this fruit is pulpy 

 and juicy, and others are hard nuts with edible kernels. 

 Some fruit is dry and inedible, and is then generally pro- 



