PARA RUBBER. 7 



Warming, after studying the vegetation of tropical America, con- 

 cluded that the latex probably served many functions, one of them 

 being a source of water supply during the dry hot part of the day or 

 year. 



Parkin* considered that the latex did not play an important part 

 in nutrition and inclined to the belief that the laticiferous system 

 served as channels for holding water in reserve to be called upon 

 during times of drought. The exudation and clotting of the 

 milk prevent the entrance of many insects, but this is not of much 

 importance. 



The complete stripping of the cortex from the base up to 5 feet, and 

 witli it the greater part of the laticiferous system, has not, in the case 

 of Hevea brasiliensis , resulted in any very bad effects on the tree. 



The present appearance of trees, from which large quantities of 

 latex have been extracted, is such as to confirm the belief that 

 the latexi s of minor importance to plants freely supplied with water, 

 and that the main source of danger lies in the removal of the corti- 

 cal and bark tissues often effected in collecting the latex. 



It should be recorded that Hevea brasiliensis grows exceedingly 

 well on land which is frequently inundated, and in some parts of 

 Ceylon I have seen trees with their tap roots and a large proportion 

 of the feeding rootlets permanently under water and yet yielding 

 over 10 pounds of rubber, per tree, per year. An abundant supply 

 of water, in well-drained land, is not harmful to Para rubber trees. 



General Considerations. 



In the accompanying Plate, No. 3, Series A, figures 1 and 2 re- 

 present the latex tubes running in a vertical direction through the 

 stem of Hevea brasiliensis. In each case they are surrounded by 

 cells which naturally store up reserve food materials, and in figure 

 2, curious rod-like bodies are seen in the laticiferous vessels. In 

 some instances the milk tubes are pitted, so that a transference of 

 solutions may be effected from one series of cells to the other. 

 Furthermore , the milk tubes often run very close to those elements 

 of the wood, the function of which is to convey watery solutions from 

 the roots upwards. Figure 3, drawn from a section of the fruit wall 

 of Carica Papaya, shows the proximity of the water-conducting 

 elements of the wood to the latex tubes, the latter possessing ir- 

 regular patches of coagulated indiarubber. In figure 4 the general 

 outline of a series of tubes is shown. On account of these 

 relationships one may be inclined to attach some importance to the 

 theory that the milk tubes are partially connected with conducting 

 functions. 



But the fact that the laticiferous tubes may be concerned in con- 

 ducting solutions, that they contain in their earlier stages a certain 

 quantity of protoplasm, and that nuclei and starch grains may be 

 occasionally found, does not exclude the view that they are mainly 

 excretory or act as water reservoirs. 



* Parkin, 1. c. 



