The Introduction of Commercial Crops.—The problem can only be satis-

factorily approached by way of a preliminary and exhaustive examination of the

conditions actually obtaining ; followed by a study of research in other regions

directed to a determination of the circumstances of climate and soil best suited to

the growth of specific crops. An attempt may then be made to secure com-

parable conditions locally. The degree of control over the various factors

involved, which may be assured by ordinary and commercial measures, is

strictly limited, and the results can only approximate to a previously determined

optimum. From this circumstance will arise the need for further inquiry as to

the separate and combined effects of temperature, moisture and sunshine, both

in their normal and abnormal proportions, upon the annual yields of staple

crops. With this must be coupled a determination of the tolerance or adapt-

ability of exotic plants to the altered conditions which will furnish a measure of

their acclimatisation.

A Problem of Acclimatisation.—Three methods are available in the latter

connection. The statistical system is an early-established means of ascertaining

the effect of climate, by comparing the statistics of the successive annual harvests

in the country at large with the annual metebrologi'cal returns. It lacks

definition and scientific accuracy and has a very limited value. A second method

is based upon the experimental cultivation of plants in rooms or other structures

where temperature, moisture and other conditions are under control. Successive

slight changes in each of the factors of the artificial climate will furnish data

for the establishment of laws of acclimatisation. A less perfect application

of this system is found in comparative field experiments where a serial modifi-

cation of one factor is applied with a maintenance of uniformity, as far as

possible, in other conditions. A final method lies in the detailed study of the

individual plant accompanied by delicate measurements and microscopic

examination of the processes of growth, nutrition and transpiration, as affected

by sunshine, temperature and- moisture. The following report reflects a

preliminary inquiry into the nature of the desert environment, modifications

esfiected therein by irrigation, drainage, cultivation and manuring, and the

character of crop growth in the amended conditions as revealed by comparative

plot work, experimental cultivation of individual plants and a physiological

examination of growth processes. To ensure reliability the field and laboratory

experiments have been conducted independently and the records only subse-

quently associated. By such means mutual control and a reduction in the

margin of experimental error are assured.

The Desert Soils.—The outstanding features of all desert areas are, firstly,

the aridity of the soil. Loam is here as dry as sand or stony soil, for all kinds

of soil are alike inadequately supplied with moisture. The soil varies greatly