3*3 



of the tissues above and below the seetion any more than one 

 prevents from pressing the body by doubling its width so that 

 under these circumstances the latex should flow as strongly as 

 possible. 



A longitudinal section on the other hand gives a different result, 

 for the lips of the wound will tend to separate and the tension will 

 become weaker 



As has been shown several causes combine to make the trans- 

 verse cuts the most efficacious for allowing the escape of the latex. 

 But are we to say that such cuts are entirely to be recommended? 

 This is not our idea, for the collector has not only the actual present 

 collection to look to, but the possibility of future collections. Now 

 1 do not say that from this point of view the transverse sections 

 might not be disastrous and the more so the longer they are. 



In fact the wound made in the bark heals more or less rapidly 

 by the formation of fresh tissues and from this cause the laticiferous 

 vessels at first continuous, are now separated in segments, which 

 are the shorter the nearer the cuts are to each other. It follows 

 that the later cuts only meeting with fragments of laticiferous 

 vessels will only let out very little latex. 



In my opinion for reasons stated above it will be most suitable 

 if one makes transverse or oblique cuts in a vine or tree to make 

 a certain number at the same height, say three metres from the 

 ground and to recommence some time after a little lower and so 

 on till the latest cuts are close to the ground. Leaving then the 

 tree to recover for a sufficiently long period, at least a year, new 

 tissues will form inside the bark and into these new tissues the 

 original laticiferous vessels will penetrate. After this period, occu- 

 pied by the tree in producing new tissues containing laticiferous 

 tubes one can make the cuts again in the same way. In no case 

 must complete circular incisions be made as these would arrest the 

 circulation of the sap and seriously risk the life of the tree. Too 

 wide cuts also must be avoided, for the healing of a wound is more 

 difficult and long the further the edges are from each other. 



It would not be difficult to arrange a programme of a certain 

 number of experiments and observations to be made by persons 

 dwelling in the tropics and having rubber plants at their disposal. 

 The results of such investigations would be of much importance 

 for the future of the plantations actually organized in various parts 

 of the world. On this subject we shall deal again if possible later, 



Henri Li<:comtr. 



Note.- — It is not correct to say as Bonysson does (Revue Gene- 

 rale des Sciences 1899, p. 831) that "the latex is a sort of ascend- 

 ing sap." I do not think that one can show as yet any proof that 

 the latex circulates in the vessels. The fact that latex flows 

 unequally from the two lips of a cut is due to the difference of 

 tension of the tissues on both sides and the flow may be much 

 greater from the upper lip of the cut than from the lower one. I 

 have proved this in the case of Landolphia Horida, Benth. in the 

 Conservatories of the Museum. 



