The First Land Plants 
were added to the soil (per hectare, that is, 2} acres) by 
common vetch, 205 kilos. (about 4 cwt.) by peas, and 
151 kilos. (3 cwt.) by lupines, in some recent experi- 
ments. 
Now on the roots of all these leguminosz, one 
finds odd little gall-like swellings or tubercles, which 
have been investigated in many famous and classical 
researches. The first to explain them clearly seems 
to have been Schindler in 1884, who suggested that 
they were due to bacterial “friends.” Then in 1888, 
Hellriegel and Willfarth showed satisfactorily that 
bacteria formed the swellings, and that these bacteria 
obtained nitrogen from the air, and so handed it on as 
nitrates to the plant. 
Pliny, Varro, and theother practical agriculturists were 
thus shown to have anticipated our modern discoveries. 
The next point was to domesticate and utilise these 
germs in ordinary garden and field work, But the 
difficulties were great. 
These microbes have peculiar tastes. A vetch tubercle 
bacillus (Pseudomonas radicicola is its proper style) 
dislikes growing on beans or on anything except vetches. 
The vigour or virulence of the microbe varies. Some- 
times, when in captivity in a test-tube or on cotton-wool, 
it becomes weak and languid, and refuses to work or 
suddenly dies. And sometimes it gets far too strong, 
and robs its vetch or bean-root of the nitrate obtained 
by the roots. 
In good garden soil there are probably millions of 
pseudomonas germs, and the question at once occurs, 
Why then go to great expense in introducing it? But 
at first sight one would think that on poor or inferior 
soil, especially where no leguminosze had been grown 
for some years, there might be some advantage in using 
artificially bred bacteria. 
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