The First Land Plants 
this valuable azotobacter were found nestling in the 
slimy surfaces of ordinary seaweeds, living on their 
sugar (mannite) and supplying them with nitrogen.’ It 
even occurs on the exquisite fresh-water alga, volvox, 
whose little hollow spheres of bright green cells re- 
volve cheerfully in the water to the vigorous wrigglings 
of its myriads of small oar-like cilia. 
Before this discovery, it had been known that some 
bacteria had this power of obtaining nitrates. There 
are especially certain forms which live on decaying 
vegetable matter in garden soil or amongst leaf mould 
which accumulate nitrates. Of these the most im- 
portant are Closterium Pasteurianum (discovered by 
Winogradsky) and the “alinite”’ bacillus of Kruger, 
Of course in practical agriculture such microbes are 
of the greatest importance. It was not long before 
people became enthusiastic over the fascinating ideal 
of sowing bacterial seed and so adding, inexpensively, 
an enormous increase to the fertility of the soil. But 
the alinite bacillus has not yet been domesticated; it 
has only been kept in activity. 
Another nitrate-forming bacillus has been recently 
very well advertised in the English papers. Its history 
is most interesting. Pliny was aware that certain crops, 
peas, beans, and lupines, improve the fertility of the 
soil instead of impoverishing it. “The Bean... 
fertilises the ground in which it has been sown as well 
as any manure.” This fact was also mentioned by 
Thaer in 1809, and has been completely confirmed by 
the experiments of Lawes, Gilbert, and Pugh.* 
So a simple method of enriching the soil came into 
use which consists in sowing down peas, lupines, or 
other legumes, and ploughing them into the soil. This 
is quite a common practice in Germany. 
For instance, 224 kilos. (about 44 cwt.) of nitrogen 
45 
