12 Transactions. 



very just and reasonable, and is evidently based on personal examination. 

 His proposed average of ten annual rings to the inch is almost precisely the 

 same as that obtained by myself (9-7). And his estimate of 300 years as 

 the probable age of a tree with a diameter of 5 ft. at the base, if worked 

 out on the average which my figures have yielded, would only be reduced 

 to 291 years. 



But, unfortunately, Kirk proceeds to make assumptions respecting the 

 growth of larger trees, for which no sufficient evidence exists, and which are 

 altogether opposed to the information I have been able to obtain. He 

 goes on to say, " The wood of the kauri remains sound long after it has 

 passed its maximum rate of growth ; but the newly formed wood cylinders 

 are very thin, while the immense pressure exerted by the outer cylinders 

 consolidates the inner portion of the trunk so that the number of rings to 

 an inch is greatly increased. I have counted over thirty rings to an inch 

 in some gigantic trunks, so that, assuming each ring to represent only a 

 year's growth, the age of a tree 7 ft. in diameter must be 1,260 years. The 

 gigantic specimen at Mercury Bay, which is 80 ft. to the lowest branch and 

 24 ft. in diameter, must be considerably over 4,000 years ; and the fine 

 specimen at Maunganui Bluff, which is 66 ft. in circumference, would not be 

 less than 3,600 years." 



Now, the whole of these estimates rest on two assumptions : (1.) That 

 as the tree approaches maturity the newly formed wood cylinders become 

 very thin. This statement is in direct variance with my own measurements 

 of no small number of trees up to 11 ft. in diameter. (2.) That the pressure 

 exerted by the outer cylinders consolidates the inner portion of the trunk 

 so that the number of rings to an inch of radius is greatly increased. But 

 my measurements do not show that the inner rings are " consolidated " 

 in trees of large size ; and, in addition, I believe I am correct in stating 

 that authorities in vegetable physiology do not countenance the idea of 

 marked compression of woody tissue in the interior of a trunk due to the 

 successive formation of exterior annual rings. 



I have already said that the statement made by Kirk to the effect that 

 a tree 5 ft. in diameter would have an average of ten annual rings for each 

 inch of radius, and be 300 years old, must be accepted as a close approxima- 

 tion to the truth. But I fail to see how he can reconcile with it the state- 

 ment made in the very next paragraph that a tree only 2 ft. wider, or 7 ft. 

 in diameter, would have an age of 1,260 years, with an average of thirty 

 rings for each inch of radius. This is equivalent to saying that during the 

 formation of the additional foot of radius the rate of growth had been 

 diminished to a third of what it previously was. Kirk's contention also 

 implies that the 300 rings which in the 5 ft. tree occupied the radius of 

 2 ft. 6 in. had been squeezed in the 7 ft. tree into a space of 10 in. ! It is 

 unbelievable that the woody layers of a 5 ft. tree could suffer any such 

 compression. But if not, then the 960 annual rings required to make up 

 the full number of 1,260 must be crowded into the extra foot of radius, at 

 the rate of 80 per inch ! Not only is such an exceptionally slow rate of 

 growth unknown in the Coniferae, but even no approximation to it has 

 ever been recorded. It is quite clear that Kirk's two estimates are incon- 

 sistent one with the other. If the first is accepted, then the second must 

 be swept away. 



Since Mr. Kirk wrote the " Forest Flora " in 1889 no one has attempted 

 to treat the question in the only accurate manner — that of counting the 

 annual rings of growth in a sufficiently large number of sections of different 



