THE STUDY OF TREES IN WINTER 



There are two distinct plans of branching in 

 trees. When the main trunk extends upward to 

 the tip, as it does in the 

 larch and other coni- 

 cal trees, it is said to 

 be excurrent, and when 

 the main stem divides 

 into many more or &J 

 less equal divisions, -^ 

 as we find it in 

 the American 

 elm and other 

 spreading trees, 

 it is said to be 

 deliquescent, 

 the latter form 

 is the most com- 

 mon one among 

 our deciduous 

 trees. 



The inner structure of these dicotyledonous 

 trunks is seen when we examine the cross 

 section cut of a felled tree. In the centre 

 is the heartwood, the durable wood of com- 

 mercial value, the cells of which are hard and 

 dry ; next it the soft sapwood, the living part 

 of the tree containing cells filled with sap; then 

 the cambium layer, the zone of growing cells, 



5 



%*h\. 



TREE WITH AN EXCURRENT TRUNK 



