The Supplement to the Tropical Agriculturist, 



criticism is all very well in its way, and Mr 

 Petch seems very food of it (vide hia burial of 

 prunings articles) ; but what the common or 

 garden planter wants ia the right road pointed 

 out to him, with sign-posts along it telling him 

 what to do as well as what not to do. — Yours 

 faithfully, 



D. B. WILLIAMSON. 



Mr, Petch on Rubbeu-Pads and the Nokth- 

 way System. 

 We direct attention to the Government My- 

 cologist's elaborate and in many respects 

 convincing reply to Mr D B Williamson's 

 criticism of his recent report on specimens 

 of bark, with subcortaceous rubber-pads, sub- 

 mitted from an estate in the above named 

 planter's charge. The dangers of the use of the 

 pricker are once again made plain— at any rate 

 of the earlier styles of pricker ; and it is for the 

 using of this instrument that Mr Petch views 

 with this disfavour the Northway System — the 

 renewed bark showing nonlaticiferous tissue 

 under the pricker cuts, and a tendency to pro- 

 duce burrs having been noticed. Have our (Jva 

 rubber-growing friends experimented with the 

 Northway system?— and what has been their 

 experience ? We should be glad to hear their 

 views and some of their practical results. 



RUBBER PADS AND THE NORTHWAY 

 TAPPING S5TSTEM. 

 Mr. Petch in reply to Mr. D. B. Williamson. 



Peradeniya, Aug. 28th. 



Sie, — My specimens of rubber pads were ac- 

 companied by a label marked " I.G. 31.5. 09." 



It is curious that in Ceylon scientific questions 

 immediately become personal questions, and 

 are discussed as though they were political. 

 The object in discussing a scientific question 

 should be merely to ascertain the truth, and 

 all the evidence for or against must be stated 

 fairly if the participants have any claim to 

 scientific reputation ; but in a political dis- 

 cussion, the chief object is to gain an advantage 

 for one's own side, and the evidence, according 

 to custom, may be "modified" to fit the occa- 

 sion. Mr Williamson is inclined to adopt 

 political methods. He states: — 



" 1st. It is impossible for any one to force a small North- 

 way blunt pricker through nearly half-an-inch of bark and 

 also through a pad of rubber adheriDg to it and into the 

 wood as well, both because the force required is more than 

 any man could exert, and also ''ecause the pricks on the 

 small Northway pricker are not long enough to penetrate 

 right through." 



It he will read my article again, he will see 

 that the bark was only three to four millimetres 

 thick. It might have been five millimetres thick 

 when fresh, that is one-tifth-of-au-inch. The 

 total thickness of bark and pad in specimen A 

 was nine millimetres, i.e. about one-third of an 

 inch ; in specimen B it was 14 millimetres, i.e. 

 just over half an-inch, and I expressly state that 

 owing to the thickness of the pad, the pricker cuts 

 did not penetrate through B. Therefore, Mr 

 Williamson's remarks about nearly half-an- 

 inch of bark and also a pad of rubber are 

 quite irrelevant, and I am at a loss to know 

 why they were introduced, except to score 

 an entirely unjustified point. Moreover, it is 

 not correct to suggest that because the teeth of 



the blunt pricker are only 8 millimetres in 

 length, therefore it can only penetrate to a 

 depth of 8 millimetres. The body of the wheel 

 is pushed into the bark for a depth of about two 

 millimetres, forming a continuous cut connecting 

 the pricker marks. Users of improved prickers 

 will kindly observe that these specimens were 

 developed in May last. 



"2nd. When a pricker is driven into the bark and 

 wood of a tree deeply and a pad ia formed afterwards, 

 it will have marks on the inside as well as the outside 

 due to the hollows in the wood filling up with latex and 

 coagulating in that shape in the former, while in the 

 latter, of course, the pushed-in bark will show on the cl se- 

 fitting pad, and will correspond with the inside marks." 



The pushed in bark is in small fragments, and 

 if pushed in by the pricker before the formation 

 of the pad, it would be pushed into the hollows 

 in the wood : the fragments are not united to 

 the main bark. If the pad were caused by 

 the inflow of latex after pricking, it would 

 bear projecting teeth of rubber correspon- 

 ding to the marks in the wood, and also 

 similar projecting teeth on the outer sur- 

 face corresponding to the holes in the 

 bark. Mr Williamson will admit that latex 

 would issue through the pricker holes? But 

 the actual examples have projecting teeth on 

 the inner side and incisions on the outer I Again, 

 on Mr Williamson's theory, the particles of bark 

 would be on the ends of the inner projecting 

 teeth, whereas they are actually, as I have 

 stated, "within the pad," at the base of the 

 incised pricker marks, nearer the outer than the 

 inner surface of the pad. It is impossible that 

 they should get into such a position, and that 

 the pad should bear actual incisions, except by 

 pricking after the formation of the pad. A 

 further point against Mr Williamson's theory is 

 that there are no projecting teeth on the inner 

 surface of the thicker pad; the pricker for some 

 reason did not reach the wood there, though it 

 did everywhere round it. The reason, of course, 

 is that the pad was already in existence and 

 too thick for the pricker to penetrate. 



"Scraping kills the bark in patches when 

 sunlight comes in contact with it " is what I 

 might have written— if I had not preferred to 

 be less positive on the matter. My statement 

 was that the bark died in patches in conse- 

 quence of the scraping. It would have been 

 better to have written "after" the scraping. 

 There is no doubt that trees have been scraped,' 

 if not done too deeply, without subsequent 

 injury in many cases. We have yet to discover 

 why the patches die in other cases. Sunlight 

 was ottered as a possible cause ; "there seems 

 to be no explanation, other than exposure to 

 sunlight, etc." Mr. Williamson's experience 

 does not negative the possibility. It may pos- 

 sibly occur, not when the whole stem is exposed 

 to sunlight, but when a narrow beam strikes 

 a small area. That could be obtained through 

 the foliage in a heavily-shaded spot, 



I have seen many rubber pads on trees which 

 have not been pricked, or tapped in any way ; 

 but I have not yet found any evidence to aiter 

 my conclusion that the bark must separate from 

 the wood before the pad can be formed. My 

 views on the Northway system should be well- 

 known, whatever their value may be ; I havo 

 never claimed that they were based ow the for- 



