OBSERVATIONS OX CANADIAN CONIFER.E. 

 No. IV. 



VARIATIONS OF ZONES AND GROWTH-RINGS IN PSEUDOTS0GA DOUGLASII. 



3S 



No. 3.5. 



No. 2. 



No. 789. 



No. 428. 



No. 3lt). 



Total width of zone, cm 



!Numl)er of rings 

 Average width of rings, mm. 



i Total width of zone, cm 

 Number of rings 

 Average width of rings, mm. 



I Total width of zone, cm 

 Number of rings 

 Average width of rings, mm. 



/■Total width of zone, cm 



■! Number of rings 



1^ Average width of rings, mm. 



^ Total width of zone, cm 



■ Number of rings 



(.Average widtli of rings, mm. 



Totals, mm 



Averages, mm 



Zone 1. 



212 



.5 

 4-24 



000 







000 



17 07 



39 



4-38 



2-72 



a 40 



16-28 

 Si 



4-9(> 



16 -95 

 4-24 



Zone 2. 



15-77 



73 



2-16 



11 95 



50 



2-38 



2-85 



10 



2-85 



16-38 



66 



2 .Ï9 



4-42 



17 



2-60 



12-51 

 2-50 



Zone 3. 



16-48 

 141 

 1-17 



4-52 



38 



1 19 



4-77 



27 



1-70 



0-70 



4 



1-75 



3 23 



28 



1-15 



6-96 

 1-39 



Zone 4. 



0-00 







000 



00 





 00 



1 36 

 14 



97 



00 







00 



0-85 



10 



0-85 



1-82 

 91 



The variations thus indicated are generally accompanied b_y a more or less marked alter- 

 ation in tlie relative volumes of the open spring and the dense summer wood, and as there 

 may thus be both "coarse-grained" and "fine-grained" wood within the same tree these 

 considerations have a somewhat important economic bearing. 



The first impression conveyed to one, upon examining these zones of growth is that 

 they correspond to and have their origin in periodicity of climatic conditions, but upon 

 farther examination this view is found to be untenable. 



In the first place we find that timbers cut from different localities and under somewhat 

 diverse meteorological conditions unifoi-mly show the same zonal development, and that 

 there is an exact correspondence between the successive zones of different trees. "Were 

 these zones also to correspond to identical chronological periods, there would be good reason 

 for accepting the view of their dependence upon periodicity in meteorological conditions, but 

 it is more than probable that, where several specimens have been cut at ditferent times and 

 in different places, there is no chronological correspondence between either the growth-rings 

 or the zones of growth which they form. 



In the second place, for the proper support of this theory, trees from the same locality, 

 and therefore subject to the same surrounding conditions of growth, should show a corre- 

 spondence in similar zones with respect to volume. This we find is not the case. Thus in 



