PLANTS THAT TELL TIME 109 



"and, departing, leaves behind it" a record for the 

 instruction and inspiration of future generations. 



The trunk of an alder is as truly an autobiogra- 

 phy as are those written of themselves by the hands 

 of men. And to one knowing and understanding 

 the meanings of its various recording marks, the 

 story is as clear as if recorded on the pages of a 

 book. 



For each year of its life the cross-section of a 

 tree trunk shows a ring. This is the diary for that 

 year. Is there a deep depression in one side of that 

 fourth year's record? Perhaps a fallen log pressed 

 against it there, temporarily hindering the tree's 

 growth on that side. Do you notice that one side 

 of the trunk is bulkier than the other? That is 

 the southern side, where the warm sun by swelling 

 the veins has correspondingly increased the thick- 

 ness of growth. Look at the opposite side and you 

 will see that the bark is thicker than on the south- 

 ern side. The tree has clothed itself more warmly 

 against the cold north winds than against the warm 

 southern sun; and on this side too you will find an 

 overcoat of green moss an additional protection 

 against cold. 



How many times have we stood beneath some 

 ancient tree and, looking up, cried hopelessly, "Oh, 

 if you could only tell us what you have seen in all 



