Plant Sanitation. 



124 



[August, 1910. 



well to note that Parkin's suggestion 

 that the present method ol re-opening 

 the cut is a deduction from his results 

 is scarcely warranted by facts. The 

 method of re-opening the cut was in use 

 iu the Straits prior to Parkin's visit to 

 the East, and it was introduced into 

 Kalutara from there. 



For several years it has been stated 

 that there is a difference in the yield in 

 Hevea from cuts which slope in opposite 

 directions,— that a cut which slopes 

 down to the right yields more rubber 

 than a cut which slopes down to the left. 

 But no figures have been adduced in 

 support of this statement, nor has any 

 experimental result bearing upon the 

 question been published. A test experi- 

 ment would not be difficult. In order 

 to avoid variations due to the tree, the 

 tapping should be done on opposite 

 sides of the same tree. The cuts should 

 be of the same length, and at the same 

 angle to the vertical, and tapping should 

 be done on both sides on the same day, 

 the latex and scrap of the two sides 

 being, of course, kept separate. Both 

 sides should be treated exactly the same, 

 except that on one side the cuts will 

 slope down to the right and on the other 

 they will slope down to the left. More 

 than one tree may be taken if desired, 

 but, if so, all should be tapped on both 

 sides. But it is not necessary to multi- 

 ply the number in order to obtain an 

 exact result. Where the difference is 

 likely to be small, a cai-eful experiment 

 on one tree will yield a more reliable 

 result than an uncontrollable experi- 

 ment with one hundred. The tapping 

 should be carefully examined to see 

 whether the cooly taps deeper on 

 one set of cuts than on the other; 

 one explanation of the alleged difference 

 is simply that the cooly finds it easier 

 to tap in one direction than the other, 

 and goes deeper into the bark when 

 tapping in the direction he finds the 

 more difficult. This explanation would 

 attribute the alleged effect to the cooly, 

 not to the tree. 



If the supposed difference can be 

 proved to be really existent, the follow- 

 ing observations may lead to an ex- 

 planation. On stripping off the bark 

 from a dead Hevea, the wood will be 

 found to be faintly ridged, more or less 

 vertically, in lines which indicate the 

 directions of the vessels in the stem. Of 

 twenty-five stems which happened to be 

 in the laboratory, it was found that the 

 fibres sloped slightly up to the right in 

 eighteen, while iu the other seven they 

 weie practically vertical. The latter 

 seven were nearly all stems nine inches 

 or less in girth, while the eighteen in- 



cluded stems over nine inches and up 

 to twenty-seven inches. It would seem 

 therefore that the slope occurs in older 

 trees, but no£ in very young trees. If 

 such a slope can be shown to exist in the 

 cortex, that is, if the latex tubes are not 

 vertical but inclined at a slight angle to 

 the right, the fact would be sufficient to 

 explain the alleged difference in yield, 

 provided that we assume, as Wright 

 and Parkin do, that the latex tubes do 

 not open into one another freely. On 

 all these points relating to the cortex, 

 however, we are still in the dark, for, 

 strange though it may appear, 110 one 

 has yet investigated mature Hevea bark 

 with the object of determining the 

 arrangement, structure, and relative 

 number of the laticiferous vessels. 

 Needless to say, the sections of seedlings 

 which were offered in 1907 do not in any 

 way contradict this statement. 



If the laticiferous vessels do slope up 

 to the right in the manner indicated, 

 and if the contention that they do not 

 anastomose freely is correct, then a cut 

 sloping down to the right will sever 

 more latex vessels than one of the same 

 length which slopes down to the left. 

 For example, if the laticiferous vessels 

 are inclined at an angle of 5° to the 

 vertical, and the cuts are made at an 

 angle of 45° to the vertical, then the cut 

 which slopes down to the right will 

 sever nearly 20 per cent, more vessels 

 than that which slopes down to the left. 

 This calculation of course assumes that 

 the vessels are distribuoed regularly 

 round the tree. 



THE FUNGI IN RELATION TO 

 AGRICULTURE. 



(From the Agricultural News, Vol. IX., 

 No. 1211, May, 1910.) 



Much misapprehension has 'existed for 

 many years, in the world of agriculture, 

 with regard to the true significance of 

 the term Fungus. In the early days, 

 when the results of abstract biological 

 science were first employed in connec- 

 tion with practical agriculture from an 

 economic standpoint, there was often 

 uncertainty, on the part of those in 

 receipt of advice, as to the place of fungi 

 among living beings. 



Thus the term came to have a some- 

 what loose significance, as is naturally 

 the case when a word is employed 

 commonly in one more or less specialised 

 relation. It is easy to understand, for 

 example, the difficulty of realising that 

 the fungus causing root disease of sugar- 

 cane is actually a relative of the grey 

 fungus so commonly found on the parts 

 of dead trees. 



