8 PARA RUBBER. 



Generally speaking the milk tubes contain an emulsion of many 

 substances, such as caoutchouc, resin, gum, sugar, proteids, al- 

 kaloids, and fats, and it is therefore very difficult to identify each 

 component in sections under the microscope. Schulerus observed 

 that in the embryo the latex is rich in suspended matters, and that 

 as the plant grows the latex becomes more watery. He suggested 

 that the emulsion of substances might be of use during the early 

 stages. He also noticed that after germination the laticiferous 

 system becomes prominent owing to an increase in the substances in 

 suspension. 



Sachs found that if the leaves of some caoutchouc plants were 

 subjected to continuous darkness the quality of the latex was 

 affected, the milk becoming less opaque ; a marked change was 

 also noticed if the plants were deprived of carbonic acid gas. 



Haberlandt and others found that in some plants the starch 

 grains disappeared from the milk tubes if kept in darkness for two 

 or three weeks, thus suggesting that under certain circumstances 

 the occasional starch grains may be converted into sugar to be used 

 by the plant. 



The presence of nuclei in certain laticiferous tubes, determined, I 

 believe, by Treub, the close association of milk tubes with conducting 

 elements in the leaf and the occurrence of minute quantities of carbo- 

 hydrates, proteids, fats, and peptinizing ferments certainly support 

 the idea that under certain conditions the latex contents may be 

 useful to the plant. These substances are present in very variable 

 proportions and the percentage of valuable ingredients in the latex 

 often diminishes as the result of tapping operations. The physio- 

 logical effect of extracting large quantities of latex from trees of 

 known age is being studied at Hemaratgoda, where tapping is done 

 more by incision of the laticiferous tubes rather than by excision 

 of dry cortical tissues, but up to the present no remarkable pheno- 

 mena have been observed. But as previously pointed out the occur- 

 rence of such material in very small quantities prevents one from 

 attributing undue importance to the " reserve food " conception. 





