In the main the most popular systems of tapping are: (_a_) One cut on a quarter of the tree, tapped daily. (_b_) One cut on a third of the tree, tapped daily. (_c_) One cut on half the circumference, tapped on alternate days. (_d_) A [V] cut on half the circumference, tapped on alternate days. Variants and extremes are: (1) One cut on a quarter, tapped on alternate days. (2) One cut on a half, tapped daily. Superficially viewed the latter is four times as strenuous as the former, and the relative position seems to be inexplicable. It may be explained that as a rule the former system is practised on old trees with poorly renewed bark, in order to allow for adequate bark renewal; and the latter is employed in opening young trees just brought into tapping, when the rate of bark renewal is at a maximum. [Illustration: TWO CUTS ON A QUARTER CIRCUMFERENCE, ON AN OLD TREE.] A few estates in this country still continue to tap trees by means of two superimposed cuts on a quarter of the tree. This was a very popular system some four or five years ago, but it has come to be recognised by practical experience that any system employing superimposed cuts leads to a high consumption of bark without proportionate increase in yield. For instance, if one compares the system of two cuts on a quarter tapped daily with a similar system employing only one cut, one finds that the major quantity of latex is yielded by the lower cut, and that the single-cut system which excises approximately half the amount of bark gives about 80 per cent. of the yield obtained by the tapping of two superimposed cuts. Of experiments to test the relative values of different systems of tapping there have been many. Most of them suffered from the initial handicap that they dealt with systems which were then popular. In order to obtain any valid result they had to be undertaken over a long period. Meantime there was a progressive movement in actual estate practice towards a greater conservatism in bark removal, and hence the experiments as originally planned lost value. Moreover, in Malaya it was difficult for experimenters to obtain practical support in the form of areas of trees suitable for experiment. As a result experiments were often confined to small blocks of trees, and a small number of blocks, from which any conclusions derived were subject to considerable errors of experiment. Often comparisons were made between only two blocks, and no allowance was made for varying factors, such as initial differences in yielding capacities of the trees, soil conditions, or the personal equation of the tappers. As a general rule, therefore, the results were vitiated to a very appreciable extent.