1888-89.] Atinual Increase in Girth of Trees. 409 



9. Of a similar nature are the questions whether, how 

 soon, and to what degree, recovery of girth-increase may be 

 looked for in trees which, after suffering from overcrowding, 

 have been cleared and opened up. I have no evidence on 

 this point, but the yew No. 47 would be a fit subject for 

 experiment, as during the decennial period, when it has been 

 much overcrowded and overshadowed, it has only increased 

 at the rate of barely one-tenth of an inch, whereas for the 

 previous sixty-four years the rate was above half an inch. 



10. Do the "annual rings" correspond strictly with the 

 age of trees in, temperate climates ? The rings in tropical 

 dicotyledons, it is well known, are not annvial, as they are 

 apt to be irregular and confused, and to immensely exceed in 

 number the years of age of the trees. From recent experi- 

 ments in the United States, it appears that even in temperate 

 latitudes the rings may be considerably greater or fewer in 

 number than the age of the trees ; and quite recently my 

 friend Mr Charles Hall of San Jorge has been led strongly to 

 suspect that in central Uruguay the rings and years do not 

 strictly correspond even in young trees. In this country, 

 however, it is generally believed that the age of a tree can 

 be told unerringly by the number of rings. This is a matter 

 not so easily proved as might be expected. It is seldom 

 that one has the opportunity of testing a tree whose age is 

 accurately known, and errors may be caused by a false appear- 

 ance of rings, by the difficulty of counting them when very 

 close to each other, even when the surface is highly polished, 

 or in the case of detached sections by ignorance as to the 

 height above ground where the section was made. Still the 

 rings and years have been so invariably found to correspond 

 closely in well-ascertained cases, that there can be little doubt 

 of their strict correspondence in healthy trees of moderate age. 

 My measurements, however, throw some doubt on the applica- 

 bility of the rule to old or prematurely old trees, as they 

 prove that such trees may not only cease to increase, but 

 may for a series of years actually diminish in girth. For 

 example, the Scots fir, No. 37, for nine successive years either 

 did not increase or actually diminished in girth, and measured 

 nearly an inch less at the end than at the beginning of the 

 nine years, and the Scots fir No. 4 diminished for four suc- 

 cessive years to the amount of half an inch in all. Now, 



