387 



after all it is the most difficult question to answer, and one they have 

 never been called on to investigate, as there is more than sufficient 

 timber for their wants. 



In India where dry deciduous mixed forests predominate, many 

 of the more important timber trees have very clearly defined annual 

 rings, due to the complete change in seasons, and a definite season of 

 rest from growth, or to the sudden and quick growth in the spring 

 when new leaves are put on. 



Thus with Teak the annual rings are so well defined that in any 

 given forest the rate of growth may be accurately gauged by means of 

 an instrument called " Pressler's borer." 



This is simply a hollow steel borer which is screwed into the tree 

 to a depth of 2 to 3 inches. Inside the tube is inserted a small steel 

 wedge-like pin, when the borer has been inserted to a sufficient depth 

 this pin is tapped smartly and then the borer withdrawn by turning to 

 the left, bringing with it a clean cylinder of wood about 2 to 2j inches 

 long. 



The rings are then counted and the length of the cylinder accu- 

 rately measured. 



It is usual to take three borings from each tree. 



In gauging the rate of growth of teak in a forest the trees are 

 divided into four classes as under : — 



Class. I 6' to 7' in girth 

 do. II 4f to 6' 

 do. Ill 3' to 4i' 

 do. IV under 3' ,, 



A hundred or more borings are made in each of these classes so 

 that trees of all sizes are gauged. Thus an absolutely reliable result 

 is obtained. Some borings which were taken in making a working napl 

 of a forest reserve in Burma may be of interest and I give them here. 



Class. IV. Trees under 3' in girth 63 bored, 189 borings average 

 annual (annual ring) .097522." Average radial increase girth incre- 

 ment .612748", therefore 59 years to attain a girth of 3'. 



Class. III. 3' to 4i' in girth 62 trees bored, 186 borings, 

 average annual ring .106043". Average annual girth increment 

 .666287", therefore it takes a teak tree 27 years to pass from 3' girth 

 to ii' in girth. 



Class. II. 4i' to 6', 64 trees bored, 192 borings. Average 

 annual ring .09408", average annual girth increa.se .591128", therefore 

 it takes a tree 30 years to pass from 4i' to 6' in girth. 



Class. I. 6' to 7' in girth, 68 trees bored, 204 borings. Average 

 ring .073362", average annual girth increase .460947", it takes there- 

 fore 26 years to pass from 6' to 7' in girth. 



Adding these results together we get 



to reach a girth of 3' p 59 years 



to pass from 3' — 4£' 27 „ 



44'-6' 30 ii 



6—7 26 



Therefore for a seedling to reach 7' in girth 142 years. 



