168 



Relation of Annual Rings to Age. 



alternate repose and activity. Plants, like animals, seem to be- 

 incapable of continuous activity, but require periods of physiolo- 

 gical rest and recuperation. Strict alternation of seasons secures 

 and defines these periods, but where the climate is of a comparative- 

 ly uniform character they must be secured by other conditions, 

 as alternation of wet and dry periods, or possibly, also, by certain 

 properties of the plant which are intrinsic ; and this appears to 

 be the explanation of the cases cited by Dr. Warring* of trees 

 growing under uniform conditions and yet developing rings. We 

 may thus state it as a general principle, that whatever tends to 

 periodicity in growth, either from external or internal causes 

 operates as a strong factor in the development of rings. 



FACTS COLLECTED. 



During the past year my friend, Mr. C. Gibb, removed the 

 chief difficulty in the way of determiniDg this question by 

 placing at my disposal several trees, the ages of which were exactly 

 known. Such, an opportunity rarely occurring, it was at once 

 taken advantage of, and the general results showing relation, 

 of rings to a^e were found to be as follows : — 



Subjects. 



Sallx r eg alls 



European Silver Poplar 



Early Strawberry Crab 



Large Striped Crab 



Quaker Beaut}' Crab 



Ite-exam. of .-tump lower down. 



Golden Sweet Crab 



Re-exam, of stump lower down 



Pirus Coronaria 



Gen. Grant Crab No. 1 



Ke-exam. of Stump lower down. 

 Gen. Grant Crab No. 3, close to 



ground 



Gen. Grant Crab. No. 4, close to 



ground 



Age. 



7 

 6 

 11 

 11 

 11 

 II 

 11 

 11 

 12 

 1L 

 11 



11 



12 



Rings 

 clearly- 

 defined 



6 

 10 

 10 

 10 

 10 

 10 

 10 

 12 



7 

 11 



11 



12 



Total i 



136 



124 



Rings 

 obscure. 



Total 

 Rings. 



7 

 6 

 10 

 10 

 10 

 13 

 10 

 12 

 13 

 12 

 11 



11 



12 



13 



137 



Again, au examination of a large ash (F. americana) } for 

 correspondence between annual rings and the annual increase in 

 length, gave the following results : — 



Amer. Jour, of Science, Vol. XIV, 1877, p. 



