484. MR. J. B. LAWES, DR. GILBERT, AND DR. PUGH ON 
adopted to avoid them. From known considerations with regard to the requirements in 
the soil and inorganic nutriment on the one hand, and in the atmosphere of the plants 
on the other, and in all combined, we have concluded what are the proper conditions of 
vegetable growth. It remains, however, to appeal to the results of direct experiment, to 
show that our adopted conditions possess the value which we have assumed them to have. 
A pot of good garden soil, capable of supporting luxuriant vegetation in the open air, 
was sown with Wheat, Barley, and Beans, and then placed under one of the experimental 
shades, and submitted to exactly the same atmospheric conditions as those provided in 
the experiments on the assimilation of Nitrogen. The result was, exceedingly luxuriant 
growth (see Records of growth in Appendix, Experiment No. 12, of “ Plants grown in 
1857,” fig. 18, Plate XV.; and also Experiment No. 15, of “Plants grown in 1858.” 
It was thus proved that the aérial conditions supplied in our experiments were adapted 
for healthy growth. 
When pots of soil, prepared precisely as has been described above, were sown with seed 
and combined Nitrogen artificially supplied, vigorous growth was the result. Hence it 
was shown that the conditions of so¢/ were properly selected. 
Section IT.—OTHER CONDITIONS OF EXPERIMENT, REQUIRING COLLATERAL 
INVESTIGATION. 
There remain to be considered several conditions which might affect the result of a 
quantitative experiment on the assimilation of Nitrogen by plants, dependent upon the 
reciprocal action of the air and the soil, with or without the connexion of the plant. 
The following conditions possibly affecting the result of such an experiment, due to the 
mutual action of the soil, air, and organic matter of the plant, require to be considered :-— 
1. The influence of ozone, either within the cells of the plant, or in connexion with 
it, in promoting the formation of nitrogenous compounds from free Nitrogen. The 
influence of ozone in promoting such formation within the soil, either directly, or in con- 
nexion with the organic matter of the plant. 
2. The decomposition of nitrogenous organic matter, in relation to the question 
whether there be an evolution of free Nitrogen in the process. 
3. The formation of nitrogenous compounds, through the mutual action of nascent 
hydrogen evolved by decomposing organic matter, and free Nitrogen. 
A.— General considerations in regard to the possible influence of Ozone on the 
supply of combined Nitrogen to growing plants. 
The consideration of Ozone in connexion with the plant suggests the possibility of its 
presence in two distinct ways. It may occur within the cells and intercellular passages 
of the plant, either in the gaseous state or in solution, or it may be simply around the 
plant, without existing within its structures. 
With regard to the origin of Ozone in connexion with the plant, it may be a product 
