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analysed, and the results com pared men the analyses of the same 
plants grown on soils provi ed wit the necessary plant-food 
stuffs. Asan important result of dio method it has been found 
that different plants take up very different quantities of the same 
mineral substances. On this is largely based the system of 
rotation of crops, where the second crop is so chosen that it chiefly 
removes the ingredients of the soil which have been left by the 
preceding crop. 
ita the aid of the cultivation method it has also been possible 
to draw up the following table which represents the relative 
values “of the different nitrogen compounds for plant-food. 
Nitrogen of Saltpetre ... = f i 100 
5 , Ammonia... dus ne .. 85-90 
a „ Albumen ... es T aes 60 
This X € be made use of in Kea the nitrogen value 
of a manure. 
The ideis method may be used for testing the value of 
f phosphate annually 
produced in Germany is now peter utilised by the e agriculturist, 
and its preparation for the r has become an important 
offshoot of the iron industry 
Similarly the sania es by the cultivation method of the 
value of potash salts in manures has given an enormous impetus 
to the potash industry. 
Speaking gener; rally, pee method gives us be hed control over 
ne ‘fertility of a soil in so far as this depends on manuring. One 
onsequence of this bia been that our views as to the value of 
agreata land have CoNIprevery changed, for whereas formerly 
sandy soils were generally considered poor, they are now, by 
means of a system of ‘intelli gently directed manuring, made to 
give yields which are scarcely inferior to those of the best soils. 
The beet- -sugar industry, Which formerly could only be conducted 
in the best soils, has now been extended with marked success to 
sandy soils. 
III. ARTIFICIAL SELECTION. 
It might seem that with a perfect knowledge of the manuring 
of plants, the need for further investigation would cease, for 
supply of excessive nourishment is a disadvantage, and only 
tends to produce sick plan is 
There still remains, however, a method by which the fertility 
of plants may be increased far beyond the limit which nature 
appearsto have fixed. "This is the method of uM selection 
which has been applied in Germany on approved 
scientific principles. German agriculture Mond hare long since 
