8 ft. 3 in. in diameter, and which had a cavity in the centre quite 18 in. across, had its external rings of growth perfectly well developed, the last twenty-five occupying a space of very nearly 2½ in., a rate of growth equivalent to 10·0 rings per inch of radius. This proportion is only very slightly under my general average of 9·7, and is well within the range of variation likely to occur. A further word or two may be expected in reference to Kirk's idea that “the immense pressure exerted by the outer cylinders consolidates the inner part of the trunk so that the number of rings to the inch is greatly increased.” But in making this statement he overlooked the immense strength and rigidity possessed by a column of woody tissue like that of a young kauri, say, 250 years of age. The already completed rings of growth, and especially those constituting the heart-wood, or duramen, have had the walls of their tissues thickened and hardened to such an extent as to constitute a framework, or skeleton, capable of withstanding any pressure that can be exercised by a newly formed woody layer. No doubt each new layer during its formation is subjected to varying strains and stresses, which modify its structure, and which, among other things, produce the well-known differences between the spring and autumn wood; but room for its actual formation is provided by the expansion of the inner cortical tissues, and the consequent fissuring or throwing-off (as in the case of the kauri) of the dead outer cortex. I conclude that Kirk was mistaken in supposing that previously formed annual rings could be materially reduced in thickness by the formation of rings of later growth, and submit the following experimental proof. The tabular statement already given shows the annual rings of growth in twenty-nine sections varying from 6 in. to 11 ft. in diameter. I propose to divide these sections into four groups, as follows: First, those with a diameter under 2 ft.; second, those from 2 ft. to 4 ft.; third, from 4 ft. to 6 ft.; fourth, from 6 ft. to 11 ft. The result is seen in the subjoined table. Group 1. Under 2 ft Diameter. Group 2. 2 ft. to 4 ft Diameter. Group 3. 4 ft to 6 ft Diameter. Group 4. 6 ft. to 11 ft. Diameter. Total Annual Rings for each Inch of Radius for Eight Sections. Average for the Whole Group. Total Annual Rings for each Inch of Radius for Seven Sections. Average for the Whole Group. Total Annual Rings for each Inch of Radius for Seven Sections. Average for the Whole Group. Total Annual Rings for each Inch oif Radius for Seven Sections Average for the Whole Group. 69·2 8·6 76·8 10·9 59·9 8·5 76·4 10·9 General average for the whole of the groups: 9·7. The above table shows no evidence of the number of rings to an inch being “greatly increased” in mature trees The averages for the various groups vary by only 2·4; and the average for trees between 6 ft. and 11 ft. in diameter, which would surely be called mature, is precisely the same (10·9) as that for trees between 2 ft. and 4 ft., and is very far removed from Kirk's suggested rate of thirty per inch for a 7 ft. tree. Irregularities in the rate of growth of individual trees, however, are not uncommon, and may occur at any period of the life of the tree. It may be interesting to give a table of the rate of growth of an 11 ft. tree, the largest I have measured, and which, curiously enough, was also the most irregular in growth. For comparison I have included a similar table of