Gums, Resins, 



100 



August, 1910. 



In the first twenty weeks, C is tapped 

 regularly twice per week, but three of 

 the other groups are tapped less than 

 once per week, and W is only tapped 

 once in two and a half weeks. In the 

 second tapping period, is again tapped 

 regularly, but the other groups are 

 tapped three or more times per week. 

 The third period suffers in the way. 

 Evidently all the groups excepi C were 

 " rushed " in order to bring the total 

 number of tappings up to the standard, 

 and as this was done especially in the 

 second period which includes the dry sea- 

 sou, the yield suffers in comparison with 

 O. Further, the more frequent tapping, 

 since the total number of tappings are 

 about equal, reduces the yield of the 

 other groups compared with C. Every- 

 thing here is in favour of group C, and 

 yet the figures do not prove it the best. 

 The yield of C is, however, quite abnor- 

 mal, as will be shown below. 



For those who wish to adopt Wright's 

 calculations as to the yield per unit of 

 bark excised, the following analysis of 

 his figures will be useful. In group C. 

 9,750 cuts remove 7,348| sq. inches of bark, 

 or 0'75 sq. inches per cut ; in group M, 640 

 cuts remove 796i sq. inches, or 1"25 sq. 

 inches per cut ; in group N, 610 cuts re- 

 move 1,472^ sq. inches, or 2 3 sq. inches 

 per cut ; in group O, 640 cuts remove 

 l,424f sq. inches, or 2-25 sq. inches per 

 cut; in group L, 1,380 cuts remove 1,666 

 sq. inches, or 1'2 sq. inches per cut ; and 

 in group W, 1,600 cuts remove 2,726 sq. 

 inches, or 1-7 sq. inches per cut. There is 

 evidently something wrong about these 

 figures. From the fact that the trees 

 diminish in girth upwards, it would 

 be expected that the amount excised per 

 cut would diminish as the higher parts 

 of the tree were tapped. But apart 

 from this, if we take the average length 

 of the cut as ten inches, then the strips 

 removed per cut in groups JS T and O must 

 have been nearly a quarter of an inch 

 wide. The calculations given are based 

 on the assumption that every tapping 

 was done by paring, but as we are told 

 that the bark was removed by paring 

 only when the yield of latex obtained by 

 pricking was considered too small, the 

 parings must have been about double 

 this width- 



The results of such an experiment as 

 this would be of considerable theoretical 

 importance, though they might not be 

 of direct use practically. But it would 

 have been preferable to have adopted a 

 system of tapping equal lengths of stem 

 at varying heights instead of altering 

 both the length tapped and its position 

 on the stem. Even then it is doubtful 

 Whether any accurate deductions could 



be obtained unless the latex from each 

 cut were collected separately. 



As the experiment stands, it appears 

 to prove that the greatest yield is ob- 

 tained by tappiug at about one-quarter 

 the height of the tree from the base. 

 Various theories could be based on this 

 result, but unfortunately it is vitiated 

 (a) by the irregular tapping, and (6) by 

 the abnormal yield of group C. 



Experiment 2. 



To Determine the Relative Value op 

 Different Methods of Tapping. 

 Three groups of trees were selected, 

 viz., A, B, and C. Each group contained 

 25 trees, and all were tapped from the 

 base to 5 ft. 6". A was tapped by the 

 full spiral, B by the half spiral, and 0. 

 by the full heriing bone, The total 

 numbers of tappings and the total 

 yield in lbs. up to the end of each of 

 the three periods into which the experi- 

 ment can be divided are : — 



A. f B. C. 



First period, Sept.-Feb. 

 37 41 39 



50£ lbs. 35Jf lbs. 47 5-16 lbs. 



First and Second period, Sept.-April. 

 57 60 57 



71 9-32 lb. 46| 72 1-16 lb. 



Total results Sept.-Sept. 



91 93 92 



82 13-16 lb. 62| lb. 75 lb. 



It will be noted that although these 

 trees are supposed to have been tapped 

 regularly twice per week from beginning 

 to the end of the experiment, the tap- 

 pings were actually irregular. In the 

 first period A loses four tappings com- 

 pared with B, and two compared with 

 C. In the second period, A gains one 

 on B, and two on C ; therefore A must 

 have been tapped more than twice per 

 week, or B and C must have been neg- 

 lected. In the third tapping period, C 

 gains one on A, and two on B. Needless 

 to say, in a comparative experiment of 

 this kind, all the trees should have been 

 tapped at the same time, even if a 

 smaller number had to be taken. If the 

 trees are tapped on different days, cli- 

 matic differences influence the results. 



From the results at the end of the first 

 period Wright states (Ed. 2, p. 96) that 

 the maximum amount of rubber per tree 

 is obtained by the full spiral. But on 

 page 99, he gives the yields for the first 

 and second period, which show that his 

 statement was incorrect at the time it 

 was published, since the full herring 

 bone has then yielded the greatest 

 quantity for the same number of tap- 

 pings. However, the final figures wh'ch 



