i 9 



transverse connections between the medullary laticiferous vessels 

 and those of the bast are non-existent in trees of such dimensions. 

 This anatomical discovery of the obliteration of the medullary 

 laticiferous vessels, accords with the observation, that if green 

 unlignified branches are cut through, there will be a small flow 

 of milk from the pith, but not in well-lignified stems. It is note- 

 worthy from an anatomical point of view, that in older trees the 

 layer of bast has been greatly thickened through the activity 

 of the cambium, and consequently the laticiferous system contained 

 in the bast has also greatly increased in size. 



Therefore, as the laticiferous vessels are situated chiefly in 

 the bast of the tree, and as the yield of latex is the greater the 

 younger the parts of the bast are in which they occur, it is surely 

 right to demand in practise, that tapping should penetrate to the 

 inner parts of the bast in order to ensure a sufficient flow of latex. 

 However, it must neither reach nor cut through the cambium, as 

 then the creative activity of the cambium would be too much 

 affected. In order to satisfy all these demands, a large variety 

 of tapping knives have, as we know, been invented. The labourer, 

 who uses one of these instruments, can without difficulty make his 

 incisions sufficiently deep, and yet not so deep as to injure the 

 cambium. Though it is true, that from even a small incision a 

 certain quantity of milk will exude, on account of the pressure 

 on the latex in the vessels, the quantity would be much too small 

 to be turned to account. Consequently we are induced to make 

 deep cuts into the stem, and not only one, but several cuts 

 simultaneously and at some distance apart, above and also along- 

 side of one another. These cuts are made on the stem in an 

 oblique direction, not vertically, as by such incisions only a few 

 of those laticiferous vessels would be severed, that run in a 

 longitudinal direction ; nor horizontally, as in that case the latex, 

 as it exudes, would not flow well, nor be easy to collect. It is 

 further necessary to make repeated fresh incisions after intervals 

 of one or two days, and these in close proximity to the old ones, 

 in order to draw from the tree the desired quantity of latex. It 

 is a very strange fact, the nature of which is not yet clearly 

 understood, 5 and which seems to have been first discovered by 



' To me it seems very probable that this so-called wound response 

 is based on the same principle as the so-called blerdin- pressure, which 

 is noticeable as the result of wounds on a stem. But it is not the 



