i6 
latex in the tree. These improvements take, however, some time, 
and the rubber planter of to-day cannot immediately benefit by the 
gradual advances made in this connection. To him it is more 
important to take advantage of methods of selection which can be 
put into practice on his plantation already started. On such a 
place it is of the greatest consequence that all unproductive, sickly, 
or otherwise unsatisfactory trees be destroyed. It does not pay to 
cultivate trees which do not give a payable quantity of latex, and 
it is a waste of land to keep the ground occupied by such trees, 
which should be immediately replaced. 
In regard to the rapidity of growth and the size of the seedling 
and the subsequent tree, it has long been conclusively proved that 
the heavier seeds are far superior no the light ones. Experiments 
conducted with a view of determining whether the size of the seeds 
have any effect on the vigour of the plant, have shown that plants 
grown from the heaviest seeds attain a greater size even if they do 
not always germinate as rapidly as the smaller. It has further 
been demonstrated that plants grown from the heaviest seeds have 
a greater power of resistance to drought. 
To insure a good stand and a greater yield, none but the largest 
and heaviest seeds should be selected, and of the seedlings the 
most rapid grower, with the healthiest and most vigourous 
appearance. 
Experiments in Improving Castilla. 
So far, very few experiments have been made for the purpose 
of .improving the Castilla rubber tree, or in order to ascertain the 
growth of the seedling under different circumstances. A series of 
such experiments were started in April and May of 1906, at 
La Zacualpa Botanical Station in Mexico. The results of these 
initial experiments are not yet available for publication, but I have 
found that so far a marked improvement is noticeable in seedlings 
placed under favourable conditions and subjected to rational 
and systematic treatment.; 
Habits of Castilla. 
When we study the Castilla in its native conditions, in the 
natural surroundings in which the tree has been able to exist and 
flourish in competition with other trees, we learn many a useful 
lesson as to its requirements under cultivation. It is by no means 
essential that a cultivated plant should always have to be grown 
under conditions identical to those of its original habitat, but we 
can always derive pointers from’ a close observation of nature. 
One of the first things we notice when observing Castilla in 
the wild state is that it prefers small openings in the forest and that 
it never selects very heavy shade. In this regard, it is similar to 
its relative the Guarumbo tree which is always found in localities 
where the primeval forest has been cleared at some time or another. 
The Guarumbo, or trumpet tree ( Cecropia ), is very common through 
Southern Mexico and Central America. It is often called the false 
rubber tree, because to the unitiated newcomer it resembles at a 
distance Castilla. As soon as a clearing is made Cecropia will gain 
