Hums, Resins, 



220 



[Sept, 1906. 



Mr. Wright :— The results up to date are as follows :— Tapping every day 

 has given an average yield of 9 lb. per tree, tapping every alternate day 11 lb. 

 per tree, and from twenty-five trees tapped twice per week 91 lb. 2\ oz., or little less 

 than 4 lb. per tree ; in the latter group, the remaining bark will last H or 

 4 years. Tapping every alternate day has, up to the present, given the best yield of 

 rubber. There is a rather peculiar feature observable in connection wich Para 

 rubber which is not always the case with other rubber trees. I refer to the wound 

 response which takes place on tapping. It has been proved to occur in the Straits 

 by Mr. Arden, and by Dr. Tromp de Haas in Java, and also by Parkin in Ceylon. 

 The time required for this wound response to take place is from 24 to 48 hours. It is 

 rather curious that that discovery should hit off the result we have obtained by 

 tapping on alternate days, or every 48 hours, compared with those of tapping twice 

 a week. 



Mr. Thornhill :— Then tapping every alternate day has given better 

 results ? 



Mr. Wright :— Yes, but I do not wish to give any appearance of finality to 

 these fragmentary results we have obtained so far. They are interesting, 

 and may some day be useful, but we may have to contradict them later. At 

 present all that can be said is that tapping on alternate days seems to be better 

 than tapping every day at Henaratgoda. 



LATEX MORE ABUNDANT IN WET WEATHER. 



Mr. Thornhill asked the reason for there being more latex during wet 

 than dry weather. 



Mr. Wright :— The reason you get more latex in wet weather is probably 

 because there is more water absorbed by the roots. The more water absorbed by 

 the roots, the more turgid the cells and the laticiferous system will become ; usually 

 there is less caoutchouc in the latex collected in wet than in dry weathei\ 



thickness op bark at different elevations. 

 Mr. Clarke :— Have you any data with regard to the thickness of bark 

 at different elevations ? For instance, at 2,000 teet is the bark thinner than at, 

 say, fifty-six feet or the normal low-country elevation? 



Mr. Wright :— I have no figures giving exact measurements, but I have 

 made observations on trees at various elevations to find out the different rate 

 of growth of the whole of the stem. You usually find that the bark at high 

 elevations is thinner than at low elevations in trees of the same age. If 

 you work out the production of bark tissue and the wood, you will 

 find these tissues are formed at a definite rate in a definite mathematical 

 proportion, so many wood cells to so many bark cells. You cannot 

 alter the proportion. If the tree grows at a slow rate it means that not only the 

 wood, but all other parts, including the bark, grow at a proportionately similar 

 rate. At high elevations the bark is usually thinner than at the low elevations in 

 trees of the same age. 



Mr. Clark :— It might be interesting to state that that clearly corroborates 

 what I experienced in South America ; I found the bark at 2,000 feet elevation very 

 thin, and there we seldom met with the trees growing in a healthy way. 



Mr. Wright :— In Brazil ? 



Mr. Clark :— No, tropical Peru. We found the bark there much thinner 

 than at 56 feet, which was the lowest point we went down in the upper reaches 

 of the Amazon. 



