68 Trees, Stars, and Birds 



leaflet. Count the dots (" horseshoe nails ") in the scar 

 of the horse-chestnut or some other tree with compound 

 leaves, and see if the number is the same as the number 

 of leaflets. 



In those trees which shed their foliage in autumn, a 

 layer of thin-walled cells forms at the base of the petiole 

 where it is attached to the branch. When it is time 

 for the leaves to fall, the walls of thesg cells break down 

 and the leaf is cut off from the tree. Sometimes an un- 

 usually early killing frost prevents the breaking up of 

 the cells of this separatory layer and the leaves cling to 

 the tree much longer than they usually do. The twigs 

 of some trees and many kinds of fruit when ripe are 

 allowed to fall by the formation of a separatory layer 

 like that which cuts off the leaves. In winter try 

 whether a willow twig will break easily from the tree. 

 Would this be an advantage to the tree if it were over- 

 loaded with snow and ice? 



Buds. At the base of the petiole is a bud ready to 

 grow the next spring. Open and examine the buds of 

 a fruit or shade tree. A leaf bud is an unexpanded 

 branch, and in the buds of some trees little leaves on 

 the sides of the branch are already formed. The branch 

 is of course very short and the leaves very small, but 

 all that the bud needs to do to become a leafy shoot 

 is to expand and grow. Can you find the young leaves 

 in the bud? Does the same bud ever produce both 

 leaves and blossoms? Does a twig bear leaves more 

 than one year? 



The buds at the ends of shoots are called terminal 

 buds. Those on the sides of shoots are called lateral 



