TREES 41 



Tree map. On the blank page opposite make a tree map of the block 

 bounded by the following streets: 



Put a dot on it for location of each tree, numbering the same sort of tree 

 with the same number. Make a list of the numbers below the map indi- 

 cating the tree to which each refers. 



Growth. Examine the twigs from the horse chestnut or the maple or 

 ash and see if you can determine the length of twig that was added last 

 year; the year before last. Draw a twig to show the marks that indicate 

 the limits of each season's growth. Make a cross-section of the terminal 

 twig and examine the end. Notice at the center the pith, around this the 

 wood cylinder, then a layer of soft tissue, just outside of which is the bark. 

 Cut a two-year-old twig. How many wood rings are there in it ? Examine 

 a cross-section of a tree trunk. Count the rings of growth. Find out from 

 your reading how nearly the number of annual rings coincides in temperate 

 regions with the age of the tree. Examine the stump of some large tree 

 to determine its approximate age. What was happening in this neighbor- 

 hood when it was a seedling ? 



The ring of soft tissue between the bark and the wood is the area where 

 the new wood and bark form. We have seen in such annuals as the weeds 

 that fibrovascular bundles are arranged in a ring. These crowd together 

 and form a new wood layer next to the old wood and a new bark layer next 

 to the bark. Between these the soft tissue known as the cambium layer 

 grows rapidly in thickness in the spring and in it the new fibrovascular 

 bundles are formed. This cambium layer is easily broken down, and it is 

 this fact that renders it possible to make the willow whistle. Find out 

 how to make the whistle and try it. In the cross-section of the tree trunk 

 notice the thin lines that run from the center toward the margin; the medul- 

 lary rays. What makes these ? 



Shade trees. What trees of our region are most commonly used for 

 shade trees? Which of the shade trees is the most ornamental? What 

 trees will grow best in sandy soil ? What sort of soil does the elm require ? 

 Is there any objection to the sycamore as a shade tree ? How extensive 

 is the root system of a tree ? What is the best time for transplanting trees ? 

 Why ? How much soil needs to be taken up with the tree ? Why are the 

 branches trimmed off pretty severely when a tree is transplanted ? 



