72 Trees, Stars, and Birds 



be noticed in the color or freshness of the bark above 

 and below these marks. By this means tell the year 

 when each part grew, counting back from the tip to the 

 base. Count the rings of wood that show where your 

 knife severed the branch. If they are hard to count, 

 try to. make a smoother cut, which may be more easily 

 done if you cut it obliquely rather than straight across. 

 If you are careful in counting, you will find an agree- 

 ment in the number of years indicated by the wood and 

 the number indicated by the bark. On some branches 

 it is hard to be sure about all the places where growth 

 was suspended. 



In determining the age of a branch you have cut from 

 the tree, do you get the same result whether you start 

 from the tip of the main shoot or from the tip of one of 

 the branchlets? If you cut across a branch above and 

 also below a place where growth began anew in the spring, 

 do you find a different number of rings of wood ? 



Opposite and alternate branches. Since branches 

 grow from buds that are at the bases of leaves, trees that 

 have opposite leaves have opposite branches also. 

 Some buds fail to grow, or a branch may break off, 

 leaving only one branch at some nodes, but you do not 

 need to look long into a maple or ash tree to see many 

 places where there are pairs of opposite branches. In 

 the elm or the birch, which have alternate leaves, you 

 will find no pairs of opposite twigs. You can therefore 

 tell by examining a tree, even in winter, whether its 

 leaves are alternate or opposite. 



Some experiments with leaves and branches. Apply 

 a drop of dilute tincture of iodin to starch paste, potato, 



