38 
SIR J. B. LAWKS AND PROFESSOR J. H. GILBERT ON THE 
acids is soluble amide, it is of interest to consider, whether plants can take up sucn 
bodies and assimilate their nitrogen ? There can be little doubt that fungi can 
utilise both the organic carbon and the organic nitrogen of the soil, though they seem 
to develop the more freely when the humic matters have not undergone the final 
stages of change by which the compound of so low a proportion of carbon to nitrogen 
as is found in raw subsoils, has been produced. 
8. Evidence as to whether Chlorojdiyllous Plants can take wp Complex Nitrogenous 
Bodies, and Assimilate their Nitrogen. 
The first direct experiments to determine whether green leaved plants can take up 
organic nitrogen were made in 1857 by Dr. (now Sir Charles) Cameron. He 
experimented with barley, in an artificial soil, and found that when urea was the 
only soil-source of nitrogen, the plants grew luxuriantly, and took up much of the 
nitrogen so supplied. Ammonia was not detected in the soil. Hence he concluded 
that the urea was taken up by the plant as such. No reference is made to nitric acid, 
and in the absence of evidence to the contrary, it is possible that nitrates were 
formed, and served as the source of nitrogen to the plants. 
In 1861, Professor S, W. Johnson, of Yale, made experiments with maize in an 
artificial soil. A given quantity of nitrogen was supplied, in one case as uric acid, in 
R second as hippuric acid, and in a third as guanine. Compared with l esults in a 
control experiment without nitrogenous supply, the growth was very greatly 
increased; and there was no doubt that the substances named had supplied nitrogen 
to the plants. Professor Johnson states, that the conditions of the experiments were 
not SRch as to demonstrate that the nitrogenous organic bodies entered the ])lants 
without previous decomposition, but from the results of Cameron, and of Hampe, he 
concludes that this was the case, 
In 1865, 1866, and 1867, Dr. W. Hampe (‘Yersuchs-Stationen,’ vol. 7, p. 308, 
yol. 8, p. 225, voL 9, p. 49, and vol, 10, p. 175) made several series of experiments, all 
by the water-culture method. Maize was the plant selected, and the sources of 
nitrogen supply were—urea, ammonium phosphate, uric acid, hippuric acid, and 
glycocoll. 
At first the experiments with urea were not very successful, apparently owing to 
an unfavourable condition of the solutions as to mineral supply. Afterwards the 
plants produced wei'e nearly as good as those grown in a garden; ripe seeds being- 
formed, which, when sown, germinated. 
Urea was found in the leaves, stems, and roots. Small quantities of ammonia were 
sometimes found in tbe solutions, but only when there was some decomposition of the 
roots or their excretions, and such formation of ammonia was tbe most prominent 
after the blooming. To obviate such formation as far as possible, the solutions were in 
the later experiments frequently renewed. In corresponding solutions without plants. 
