Vol. XIV. No. 349. 



THE AGRICULTURAL NEWS 



295 



THE EFFECT OF TAPPING ON THE PARA 



RUBBER TREE. 



Mr. L E. Campbell, B.Sc, A. I.e.. rubber research 



chemisl to bhe Ceylon Department pf Agriculture, is 



the author of Bulletin No. LG oi thai Department, 



which describes an investigati n tapping and the 



storage of planl food in Hcvea brasiliensis. From the 

 results described it may be concluded that the effect of 

 careful tapping is localized. 



Starch is withdrawn from the wood immediately behind 

 the cut, and also partially from narrow zones of bark below 

 and at each side of the tapped area. Iii the above cases these 

 zones did not exceed I. 1 , inches in breadth, and in most cases 

 the breadth was considerably less than this. The starch content 

 of the bark was, however, normal right down to the top of 

 the tapped area in the majority of cases. 



Excepting for this slight and absolutely localized with- 

 drawal of starch in the neighbourhood of the tapping cut, 

 the food supply had not disappeared from below the 



tapped area. 



It must be understood that all the trees selected for 

 these experiments had been carefully tapped, and on 

 examination of the sections during microscopical work 

 evidence of 'kiams' was extremely rare. 



In hardly any case had the tapper cut down to within 

 1 millimetre or ..'--inch from the cambium. It is probable 

 that food transport from the leaves lakes place largely within 

 this inner layer of the hark, and it is this fact which is so 

 often lost sight of in discussions on the subject. Because 

 a given tree with bark 8 millimetres thick at a given place 

 is tapped so that 7 millimetres of the 8 are removed, to say 

 that it is 'seven-eighths girdled' at that place gives a totally 

 wrong impression, tin- I millimetre remaining being the chief 

 part of the system for the conduction of food down from 

 the leaves. 



Where can less or heavy tapping ha- been employed, 

 the tapping out extends down to, or nearly down to, the 

 wood, and there is, of course, a complete severance of the 

 channelsof food transport at that place. It is unfortunate, 

 from the planter's point of view, that the latex vessels occur 

 to tic greatest extent near the cambium, but the iniquity of 

 cutting 'kiams 1 is now usually sufficiently strongly impressed 

 on the coolie. 



The conclusions may be summarized by stating that the 

 effects of tapping on the trees here described were almost 

 purely local, a result which a perusal of most of the litera- 

 ture on the subject would not lead one to expect. 



Now the premises are that intervals between periods 

 of tapping are of great advantage as regards recovery of the 

 bark. This his "however to be reconciled with the not 

 unnatural desire of directors and proprietors to obtain large 



rubber yields. 



The fact that the effects of tapping appear to be largely 

 local, especially in a horizontal direction, justifies the surmise 

 that by changing tapping from one part of the tree to another 



at intervals, the resting period of each area-, tapped is 

 nearly as effective as if the whole tree were rested. 



It would seem that the 'change over' system so regulated 

 as to accord with estate practice would be of benefit as 

 regards bark renewal, and probably of rubber yield. 



Another point of interest is that the effects of tapping 



here observed are much mop- localized than the remarks of 

 Fitting would lead one to believe. It does not follow, of 

 course, that some methods of tapping may not lie SO drastic 

 ill their action as to have a much mote widespread ell'-! OH 

 the trees than those described here, or, again, that bad 



tapping might not lead to such effects fndeed, it is possible 

 that results such as Fittin i i lined might havebeendue to 



this cause. 



It has also been suggested that Fitting's results may 



have been abnormal owing to the possibility that his trees 



were examined about the time of the wintering season, though 

 the effects of the wintering season on the I I movements of 



llevea have not been hitherto investigated. 



The Role of Chlorophyl. -A series of four 

 maize plants were cultivated in solutions which, for the lirst 

 two acting as controls, were of ordinary strength, and for the 



last two ten times as strong, approximately .'!■+ parts of 



soluble elements per 1,000. The amount of water evaporated 

 by each plant was measured, and on the twentieth day this 



loss of water was made g I by addition of the respective 



culture solutions, the strength for plants 3 and 4 having 

 reached approximately 6"2 parts per 1,000. From this date, 

 these two plants began to lag behind the controls, and six 

 .lays later the terminal leaves of plant -t were chlorotic. 

 Comparing one control and one experimental plant, it was 

 found that on the twenty fourth day the control evaporated 

 twice as much water as the other, the expenditure of heat 

 being, therefore, 180and 90 Cal. respectively. This difference 

 could not be attributed to differences either in the chemical 

 work of the plant, to external conditions, or to difference in 

 leaf surface of evaporation. It could only come from calorific 

 energy due to the transformation of luminous radiations by the 

 chlorophyl. A diminution of the activity of a plant must 

 consequently produce a decoloration of its green organs, and 

 this was found to occur in the case of plants 3 and 4, the 

 chlorosis being the means by which the plant protects itself 

 against an exaggerated rise in temperature. 



In the case of the control plant on the day mentioned, 

 when the expenditure of heat due to the evaporation of the 

 water was 180 Cal., the increase in dry weight was 2 grams. 

 For this gain in weight, about 8 Cal. were absorbed The 

 author considers that the difference comes from the 

 chlorophyl, and that it is rash to attribute to this substance 

 any immediate action on the chemical changes taking place 

 during the assimilation of carbon. The role. if the pigments 

 ..f the higher plants is purely physical. (Journal oj the 

 Chemical Society, Vols. 107 and 108, July 1915.) 



Village Clubs and Associations in England.— 



It is not too much to say that during the last century such 

 corporate life as the villages of England have enjoyed has 

 centred round their various clubs, and it is noteworthy that 

 the birth and development of these institutions have been due 

 to the associative instinct of the labourers, the artisans, and the 

 small middlemen. For a large part of the nineteenth century 

 the fanners were too prosperous to feel the need of collective 

 action, and the economic benefits offered by the usual village 

 a ■ iations were not of the kind to attract them, so that they 

 only appeared in connexion with those societies as honorary 

 members or friends. Harder times have once more reminded 

 tin in of the economy of mutual action for protection and 

 advancement, and such organizations as the Nation il Farmers' 

 Union, with its COUnty and village branches, and the various 



farmers' co-operative societies, are tic mtcome of it. lint 

 f..r a century or more it was the humble inhabitants of the 

 villages who carried on the traditions of associated life in 



rural England. (Journal of. the Royal Agricultural Society 

 oj England, Vol. 75, 161 I.) 



