and Magazine of the Ceylon Agricultural Society.— August, 1918. 191 



nation has been made under these somewhat 

 ideal conditions, further experiments are neces- 

 sary (and will be suggested a-> the outcome of the 

 series) upon the average trees met with on au 

 estate. In carrying out exp jnments of this kind 

 two qualities are essential ; first, keen obser- 

 vation, and second, absolute accuracy. These 

 two points must be guaranteed if the results from 

 all the experiments are to be used as a guide. 

 Points to be Bokne in Mind. 

 With the object of increasing the value of the 

 document seut out officially, we have several 

 suggestions to mike. Jn the first place we think 

 it advisable to determine the value of tapping 

 periodicity not only at three, four, five and seven 

 diy inteivals, but at intervals of one and two 

 days. At the present time most estates are tap- 

 ping each tree • ;ai ly, or every alternate day, and 

 the point of moat interest is whether tbe other 

 frequencies mentioned are better than those now 

 commonly adopted. W i have therefore in some 

 of the forms sent out to managers added one 

 d.»y and two day intervals. This should con- 

 siderably enhance the value of the results ob- 

 tained. 



The second point is in relation to the num- 

 ber of trees in each group. It is obvious to 

 everyone who has had practical experience in 

 tapping, that the quantity of latex obtained from 

 apparently similar trees varies considerably. 

 The only way in which this variability can be 

 minimised is to take in a very la r ge number of 

 trees, aud to continue the experiments over a 

 very long period of time. There are, however, 

 m most of the estates where the experiments 

 jan be conducted, limitations in this respect. 

 As a practical suggestion we would reque t 

 each manager to reserve 100 tret s in each of tne 

 groups enumerated. 



The third point, which appears to bo of per- 

 haps the greatest importance, is that the tre-s 

 to be experimented upon should be equal in all 

 respects as far as possible. They sh mid be of 

 even appearauce, age, an 1 siZh ; they should be 

 the same distance apart, on soil of similar charac- 

 ter and aspect, and grown under the same 

 system of cultivation. The reason for this sug 

 gestion regarding equality will be at once clear 

 to every pJa iter. The yields obtained from the 

 same aged tre '8 on the top of a hill would be 

 widely diffjre it frym th >se obtaiue i at the base 

 of the hill. Similarly the croos trora tiees of 

 the same age, but plauted at different distances, 

 with or with mt intercrops, would show big 

 variations. If one does not s 'cureidentical con- 

 ditions as far as the pla ts aud their environ- 

 ments are concerned, the results will be of no 

 value ; too much importance cannot be laid on 

 th s p «int. 



The lourth point we wish to bring for- 

 ward is that in relation to the condi- 

 tion of the trees ou which the experi- 

 ments are to be made. We would prefer that 

 the trf es to be tapped should either never have 

 been tapped previously, or have been tapped 

 to approximately the sa.oe extent. Our reason 

 in suggesting this is that if trees are selected 

 which have been tapped in different ways, the 

 results trom them, even if tapped at the same 

 frequency, would not be identical. Trees which 



have been tapped have usually had the bark 



removed in a more or less systematic manner, 

 but if the quantities of bark removed and the 

 methods of tapping employed in the past are 

 not identical, then the experiment would not 

 be of much value. It is extremely difficult to 

 determine the effdCt of past tapping on luture 

 yields at sight, an i therefore we would prefer 

 that the trees selected should not have been 

 previously tapped. This would give, in our 

 opinion, more equal conditions than any other 

 .system of selection. 



Our fifth point is in relation to the tapping 

 lines an.n the bark shavings. It is not sufficient 

 to ask for the number of inches of bark, be- 

 tween the parallel tapping lines, excised from 

 above downward*; is it in our opinion necessary 

 that the tai ping lines on all the trees should be 

 of exactly tne same length, and sloping at the 

 same angle. If the lines are not of the same 

 length, than the yield will va r y apart from the 

 system of tapping ; if th".y do not i-lope at the 

 same angle the same result would fellow 



With reference to the baik shavings removed 

 during each tapping operation, we suggest that 

 it be of the *ame or minimum size and depth, 

 and that the tapping experiments on all trees be 

 commenced at the same date. 



As a last suggestion we would point out the 

 necessity of keeping all records of rubber, in- 

 cluding first quality, lump, scrap, and earth, quite 

 sep .rate. 



We trust that the suggestions we have made 

 will enable those who undertake the experi- 

 ments to eliminate many of the errors which 

 they will otherwise have to contend with. It 

 must be borne in mind that tbe variability in 

 yielding-capacity of Hevea bark is enormous, 

 and that many other suggestions could be put 

 forward which would reduce the liability to 

 error. It must not be expected that the results 

 in the different countries will be idetitical, or 

 that those from even different e&tates in thesame 

 island will be the same. We anticipate widely- 

 different results from the wet, black soils of 

 Klang. the light volcanic soils of Sumatra and 

 Java, aud the rocky hillside of Ceylon ; but we 

 also realise that the results will s^rve as a step- 

 ping-stone to further experiments which will, 

 if properly conducted, he of re*l value to the 

 planting community.— Indii Rubber Journal, 

 July 20. 



RUBBER TAPPING AND BARK 

 RENEWAL PERIODS. 



Oru readers will remember that some time 

 ago we had an opportunity of drawing atten- 

 tion to certain Ceylon experiments with Hevea 

 trees. The statement we questioned was one 

 to the effect that the interval between suc- 

 cessive tappings, provided that it does not 

 exceed a week or so, makes no difference to 

 the yield of rubber per tapping. We have 

 given our view of results obtained by tapping 

 every day or every alternate day, and the 

 reasons which have led us to advocate a mini- 

 mum period of four years for baik renewal. 



[From thuTropicril Aqriculturist for May, 1912, 

 Br. Lock's views are then quoted.] 



