66 
SIR J. B. LAWES AND PROFESSOR J. H. GILBERT OH THE 
Examination showed that the plants which did not develop beyond the first period, 
had either no nodules on their roots, or only weak indications of them; whilst the 
roots of the plants which developed favourably, had the nodules, and the more, or the 
older and stronger, the nodules, the better was the development of the plants. He, 
therefore, instituted experiments to determine whether by the supply of the organisms 
the formation of the root nodules and favourable growth could be induced ; and on the 
other hand, whether by their exclusion the result could be prevented. 
To each of ten out of 40 experimental pots, with nitrogen-free soil, 25 c.c. of an 
extract of fertile soil, made with five times its weight of distilled water, was added. 
After a time the plants in each of the ten pots regained their green colour, and grew 
vigorously; whilst in only two of the thirty pots without the addition of the micro¬ 
organisms did the plants develop favourably, all the rest showing more or less 
nitrogen-hunger, and some were quite yellow. After a time the plants from two of 
the pots with bacteria, and from five without, were taAen up, and examination showed 
very strikingly the connection between the amount of above-ground growth, and the 
development of the root nodules’. In the 8 remaining pots with bacteria, the growth 
was very uniform ; whilst in only 4 of the remaining 25 without bacteria was there 
fair development. 
Hellriegel states that the quantity of soil extract added contained only 1 millig. 
nitrogen. In two other experiments everything was sterilised. The peas germinated 
healthily, developed their first 6 leaves, but did not go further, and died, not a trace 
of nodules being found on their roots. He concludes :— 
To the nourishment of the PapilionaceEe, especially their assimilation of nitrogen, 
the so-called leguminous nodules, and the micro-organisms they contain, stand in 
close and active relation. 
It was remarkable, however, that in numerous trials with lupins, under exactly 
similar conditions, successful second grov/th could not be obtained. The conclusion 
was, that the organisms in the root nodules of lupins were of another kind, which 
were less generally distributed than those found in the nodules of peas. Further, it 
is known that lupins do not grow well on a heavy, or even on a rich humus soil. 
Three rows of the experimental pots were filled with cjuaidz sand, a nitrogen-free 
solution was added, and lupins were sown. A portion of diluvial sandy soil, where lupins 
were growing well, was treated with 5 times its weight of distilled water, and a turbid 
extract was obtained, in which it miolit be assumed that there would be a sufficient 
quantity of the micro-organisms peculiar to the sandy soil. To each experimental pot 
of the first row, 25 c.c. of this fluid was added ; those of the second row were left 
without any such addition ; and those of the third row received the extract from the 
loamy humus soil, the same as was used in the case of the experiments with the peas. 
The germination and early growth were favourable in all cases ; then followed the 
hunger-condition, and after 30 days from the sowing, all the rows showed equal 
poverty. Then the lupins of the first row began to show fresh green colour, assumed 
