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carbohydrates which can be readily changed from one to the other 

 by the action of an enzyme, and when they are to be transported 

 from the soluble substance and, when stored, the solid substance. 

 This state of things seems to be the same in all latex bearing 

 plants, as all that I have examined contain this watery solution 

 and the solid globules, though the watery solution does not always 

 turn black and the solid globule is not always rubber, but some 

 times a sticky substance. 



Dr. Weber asserted that the black water was due to oxidation 

 and he believed that rubber itself was an oxidation product. Latex 

 which is gathered and quickly corked up away from the air, 

 forms no black water. Black water gets blacker for longer stand- 

 ing in the air until about five days after gathering. Fresh black 

 water can immediately be turned to its deepest black by ammonia, 

 but ananonia will not affect black water five days old. I believe 

 that the action of ammonia is the same as the oxidation in the 

 air. Contact with metals will make black water blacker. Sugar 

 slowly takes the black colour away and latex which has not been 

 allowed to oxidize has water which resembles that formed by 

 sugar. I believe that sugar reduces it to its former state. I do not 

 see any reason to think that rubber itself is an oxidation product. 

 It is possible, but if so it can be further oxidized by the use of 

 nitric acid. 



The problem of tapping has a great deal to with how the latex 

 is situated in the tree. According to most writers it is carried in 

 " milk tubes" which are in the bark and are arranged vertically. I 

 have not found any writers who seem to know what these milk 

 tubes are like — whether the latex runs up or down in them, or 

 what connection these milk tubes have with other parts of the 

 plant. When I first got here I tried a number of experiments, 

 trying to increase the flow of latex by multiple tapping, gradual 

 tapping, and so on, but all these failed. The reason for these 

 failures I now attribute to the shape and position of the latex 

 carrying tissue in the plant. This tissue, I believe, is the part 

 known as the bast fibre. Bast fibres are long fibrous threads, 

 tapering to a point on each end, having a thick, tough wall and in 

 most plants dead, and containing nothing in the cell cavity. 



In the Castilloa, the microscope shows that the bast fibres have 

 a larger cell cavity than in most plants. It is reasonable to sup- 

 pose that they are in such cases alive and contain something. I 

 have seen no other tissues in the Castilloa bark which contain the 

 latex and therefore believe that these bast fibres do. The bast 

 fibres are arranged vertically and are probably only a few inches 

 long. Those I have examined in temporary branches were from 

 I to 3 inches, but they are probably longer in older parts of the 

 trees. The fibres are probably connected to each other by pits 

 but I have not been able to locate these connections. These pits 

 would not allow solid substances to pass from one fibre to another, 

 but would allow water and watery solutions. 



The rubber being in solid globules is probably formed right in 

 the fibre itself. The fibres are not arranged in regular joints, as 



