22 
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 th‘6 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 notits 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 when 6 years old, in other places not before 
io 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, tha«t is 5 Jo 10 years ago. Now I 
would say that the gathering of rubber from trees less than 8 years 
old is n£t likely to be advantageous. On Zacualpa we tap in the 
7th year all trees withuagirtl} of 28 ( inches at three feet from the base. 
Such a tree takes four ifiprsions, nine inches long. In the 8th year 
we expect to tap all tree? 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 s£em 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: — 
