32 



How are we to explain the fact that Castilla in some places in 

 the mountains of Southern Mexico, where the rainfall is high and 

 the atmosphere laden with moisture, does not produce latex, or at 

 least a very small quantity ? I take it to signify that in those places 

 the transpiration is less than on the plains. This is, of course, 

 only assumption, and the question is still open. 



It has been claimed by certain theorists that the sole or 

 at least the principal function of latex is protection against the 

 natural enemies of the plants. How is it then that those individual 

 trees of the same species, which do not produce latex, are not 

 instantly devoured by insects and other pests ? Let those who 

 know answer this. I think that the conclusion of latex being solely 

 a protection against insects or other animals is as narrow as the 

 theory that spines are developed on certain plants for the same 

 purpose, solely for the protection against animals. No plant 

 physiologist or ecologist who has studied the question in nature 

 would now-a-days maintain this. I do not deny that latex in the 

 rubber trees may incidentally be a means of protection also against 

 insects, but this certainly is not its main function. 



Tapping Operations on La Zacualpa. 



There has been a great difference of opinions as to the age at 

 •which a Castilla tree can be tapped. We have, however, to go 

 more by size than by age. In one district the average tree may 

 reach a tapable size w^hen 6 years old, in other places not before 

 lo years of age. A definite rule can therefore hardly be laid down. 

 The term of 6 years was tentatively put forth by most planters in 

 the early days of planting, that is 5 to lo years ago. Now I 

 would say that the gathering of rubber from trees less than 8 years 

 old is not likely to be advantageous. On Zacualpa we tap in the 

 7th year all trees with a girth of 28 inches at three feet from the base. 

 Such a tree takes four incisions, nine inches long. In the 8th year 

 we expect to tap all trees down to 25 inches, and this minimum 

 girth for a tapable tree will then be maintained. After the 8th 

 year the greater number are probably ready for tapping. One 

 incision drains a larger area on the stem than in Hevea. 



It is well known that rubber from three to four year old trees is 

 decidedly inferior. Consequently we cannot go by size alone when 

 we speak of young trees. The size has, however, more to do with 

 the productiveness than the age. But we must take the 

 "maturity" of the latex into consideration. 



In order to keep track of all work performed on the plantation 

 a series of observations are to be made by the assistants, and the 

 data thus obtained will serve as a guide in laying out our tapping 

 plans. 'As I have already mentioned the plantation on La Zacualpa 

 is laid out in square blocks. All records in connection with each 

 separate block are filed on cards, such as are now common in most 

 American business houses. The blanks are printed ready and 

 the cards appear something like the following figure, when completed 

 with notes: — 



