F. B. GUTHRIE. LXI, 
tins, and were quite moist on arrival. The nitrifying 
organism was present in large quantity, and its develop- 
ment was extraordinarily rapid. Hxcessive heat has, of 
course, also a detrimental effect upon these organisms, and 
both excessive heat and want of moisture are conditions 
which prevail in the class of soil under discussion. Hence 
these soils are characterised by the slowness with which 
the nitrifying process takes place, but although the vitality 
of these organisms is impaired, or their condition modified 
to the extent that their development is exceedingly slow, 
in no case are they absent, and, when once they com- 
mence to develop, the development continues at a nor- 
mally rapid rate. The conditions which favour their 
development within the soil, namely, aeration, moisture, 
and equable temperature, are conditions which will result 
from properly conducted irrigation. Similarly, the nitrogen- 
assimilating organisms which occur in the root-nodules of 
certain plants depend, of course, upon the vigorous growth 
of these plants, and, without irrigation, it appears hopeless 
to attempt to grow leguminous plants in these districts. 
Quantity of water required by different Crops.—I do 
not propose to go deeply into this subject. A large number 
of careful experiments have been, and are being, conducted, 
more particularly in Germany and America, to establish 
the requirements of the different crops with regard to water. 
All growing plants and trees are continually pumping up 
water from the soil and evaporating it through their leaves. 
The surface of an area of cultivated land exhales enormous 
quantities of water as vapour into the air. This free pas- 
sage of water through the plant appears to be necessary 
for its growth, and though cases are known in which plants 
have been able to adapt themselves to circumstances and 
to grow in a very limited supply of water, still for the 
normal production of crops it may be assumed that sufficient 
water for this purpose is essential. 
