BOTANY FOR YOUNG PEOPLE. 147 



L. I should think that was hardly needed as 

 a distinguishing mark. We can tell endogenous 

 trees by not giving off branches and the bundle 

 of leaves at the tops. 



E. There is another external mark, the veins 

 ~in the leaves, or woody lines run parallel to 

 each other, and are generally long and pointed ; 

 while in the exogenous plants they form an in- 

 tersecting net work. 



The first year there is a layer of woody mat- 

 ter around the pith between it and the bark ; 

 during cold weather vegetation ceases. The 

 second year there is another layer added outside 

 the first layer and inside the bark; this last 

 squeezes the first so tightly that it cannot ex- 

 pand at all sideways, and as it continues grow- 

 ing must shoot upward. The third year an- 

 other layer encloses the second, and serves it as 

 it has served the first, so that the second is 

 forced upwards in same manner. In three 

 years then, there are three layers, the first of 

 which is highest, the second next in height and 

 the third lowest, thus explaining it conical form. 



L. If we could see the different layers of 

 wood I think we might easily tell the age of the 

 tree. 



