258 



the lactiferous system acts as a specialised or reserve storage of 

 water. In a previous report we have called attention to the varying 

 dimensions of the girth of a Para tree during the course of a day. 

 We pointed out that a tree measuring 3 feet in girth, at 3 feet from 

 the ground, in the early morning, might contract as much as half an 

 inch by mid-day on bright sunny days, and conversely, on sunless wet 

 day be swollen to tension point and measure over 3 feet in girth. 

 The tree is a true hygrophyte and is capable of absorbing and 

 evaporating an enormous quantity of water, but — as shewn by the 

 fall in girth on sunny days— evaporation is so much more rapid than 

 absorption— and considering the soft outer layers and large pores of 

 the wood- the tree would doubtless be wilted except that it does ap- 

 pear there is a minimum limit below which the latex never falls, and 

 trees tapped late in the day yield very little or not at all because the 

 pressure of water necessary to complete exudation — after the tubes 

 or sacs have been wounded or punctured — is insufficient. 



What really occurs may be expressed as wound response but in 

 effect, and as judged by results, it is the compensating action of the 

 tree in replacing escaped water and it would appear in excess of 

 normal during a tapping period or season. This appears so from 

 several phenomena, the most important being : 



(a) the change that always takes place in the colour of pre- 

 pared rubber from a yellow tint to white. 



(b) increase of latex. 



(c) shrinkage of prepared rubber to volume of latex. 



{d) return from the excess of latex to normal in volume, 

 colour, and weight after a period of rest. 

 The change referred to in the first three instances takes place 

 between the fifth to the tenth tappings and appears to be entirely 

 influenced by the number of tappings and not by the time elapsed, 

 thus : 140 trees tapped in May on alternate days and in the following 

 December and January daily, exhibited increase of latex on both 

 occasions after the sixth tapping, although 12 days had elapsed in the 

 first against 6 days in the latter instance. The increase of latex or 

 wound response " is variable, however, and is usually exhibited in 

 the second and subsequent periods of tappings after fewer tappings 

 than on the first occasion. 



i^jj Change in colour. There is always a change in colour 

 of coagulated rubber, when the trees have been tapped 

 periodically, and this change, from a tint of yellow to 

 white, takes place at the time of increase of latex. It 

 should be noted that at seasons of heavy rainfall coa- 

 gulated rubber is then white as a consequence of e.xce^- 

 sive moisture. 



(h) Increase of latex. Most noticeable after the sixth tap- 

 ping and with the increase comes the change of colour 

 referred to. 



ic) Shrinkage. The quantity of coagulated rubber is not in 

 exact ratio of the increased volume of latex. For some 



