430 The Philippine Journal of Science 1921 
salt in solution. The movement of water is increased in this 
way ; consequently, the roots are always well supplied, especially 
in locations where the irrigation ditches are constantly filled 
with salty water. Experiments elsewhere have shown that not 
all soils are benefited by salt application. 
It would seem that the beneficial effect of salt in the Nakom 
Chaisri orchards is primarily due to liberation of certain plant 
nutrients and increase in the film movement whereby the roots 
are constantly kept abundantly supplied with water. The chem- 
ical effect of salt, when taken into the plant, especially in 
relation to sugar transport, may also have some bearing on the 
quality of the fruit. Further experiments would have to be 
conducted to determine these points. 
Another important point in the production of high-quality 
fruit is general culture. The Kao Pan is not an extremely hardy 
and robust tree and responds readily to culture. The orchardists 
who produce the very best fruits are those that use the most 
careful orchard practices, such as the selection of a proper or- 
chard site and the practice of proper irrigation, cultivation, 
fertilization, and cleanliness. The best orchards have been lo- 
cated in the Ban Mai region where the salty character of the 
Tachin River appears to be at its best. The growers in these 
regions have small holdings and take exceptionally good care of 
their trees. The nearness to the river does not appear to make 
any difference, as orchards located on the banks and others a hun- 
dred meters from the bank produce fruit of equal quality. The 
height of the land above the water, according to the growers, 
has some effect on the fruit ; for, if the land is a little too high 
above the water, the best pummelos cannot be developed. This 
would indicate that irrigation with a constant supply of water 
is essential. Keeping down weeds and the production of a dust 
mulch are practiced in the best plantations. The application 
of fertilizer, such as wood ashes or paddy ash and canal mud, 
at least once each year, is essential. Pruning of all dead 
branches and removal of parasites such as Loranthus must be 
done to obtain the best results. Trees in neglected orchards, 
even in the heart of Ban Mai district, are sickly and dying, 
and they produce a distinctly inferior fruit, with thicker skin and 
poorer flavor, than do neighboring orchards where the best 
attention is given. 
It appears from these investigations, that Kao Pan trees grown 
out of the Nakorn Chaisri region, even when the salt require- 
