172 



ing, but this must be done gently and can only be done after the 

 addition of water. It is advisable also to stir the mass while boil- 

 ing slowly to prevent the formation of a porous mass in which por- 

 tions of uncoagulated latex may be included. After coagulation 

 the rubber must be carefully washed. 



NOTES ON THE "CASTILLOA" RUBBER 

 TREE-II.*^ 



By "A. Forester," Bluefields, Nicaragua, February 1906. 



What latex is to the tree is still a debatable question. I think 

 that it is simply a protection against insects and evaporation 

 whenever the tree is wounded. Anything striking against the out- 

 "side bark, if it hits hard enough, will bruise the inner bark so that 

 the latex flows. An examination of this place a day or two later 

 will show a thin coat of rubber entirely covering the bruise. Tro- 

 pical trees do not have the thick outer corky bark of northern 

 trees. Anything striking them is liable to bruise the inner bark. 

 This sheet of rubber forming would protect the bruise from too 

 much evaporation and from insect attacks. Leaf cutter ants do 

 not attack the leaves of Ccistilloa and cattle do not seem to be fond 

 of them, but I believe that this is not due to the latex but due to 

 the thick coat of epidermal hairs, a thing which few tropical trees 

 seem to possess. It is noticeable that ants do attack Hcvca which 

 has not a hairy leaf. 



The study of the structure of the latex shows that it has two dis- 

 tinct parts — watery solutions and a solid substance in minute glo- 

 bules. The watery solutioi>s contain no rubber. They do contain 

 the substance which forms the residue of the black water, though 

 this substance is apparently changed by oxidation before becom- 

 ingblack water. They may also contain sugars and proteids, as 

 these substances are evidently there, but it is more than likely that 

 these substances are not in the original latex but come from some 

 other bark tissue than the "milk tubes." 



The solid globules are principally rubber but they are said to 

 be surrounded by protoplasm and contain a nucleus. In that case 

 they would be cellular in their nature. As the tube in which they 

 are enclosed is already a cell, it would be a case of a cell within 

 a cell, which is rather rare in botany. At the same time they are 

 very small for cells. I have not been able to examine the structure 

 of the single globule, as my microscope is not powerful enough, but 

 I think that they are not cellular but are originally chromotophores 

 in which rubber has been stored. In that case they would be 

 forrsed in a similar manner to starch grains in a potato and other 

 roots. I believe that this is the case and that the substance in so- 

 lution, later forming the black water, bears the same relation to 

 rubber that sugar does to starch ; that is, they are similar forms of 



♦From the India Rubber World. Continued from Bulletin for May. 



