Total Nitrogen Content of Foliage Leaves. 517 
Otto and Kooper (8) have made a careful examination of the morning 
and evening nitrogen content of the leaves of Aescuhts hippocastanum , 
Phitadelplius coronarius , Phlox Drummondi , Sambucus nigra , and Syringa 
vulgaris . Leaves were picked at 6 p.m., and at 6 a.m. the following 
morning, at frequent periods throughout the season. Samples were picked 
with care from plants of the same age. They express their results by 
Method B, showing in all cases a very small fall in the nitrogen content at 
night. As it is impossible to believe that the leaves become richer in sugars, 
&c., through translocation into the leaf, their results undoubtedly do indicate 
a fall in the nitrogen at night. But it would appear that the authors did 
not completely realize that they were only comparing relative concentra¬ 
tions in terms of total solids, as mentioned earlier on page 513. Unfor¬ 
tunately Otto and Kooper do not give the fresh weight of the leaves used, 
so that an estimate of the actual fall in the nitrogen content at night 
cannot be calculated by Method C. Their results, then, though they 
undoubtedly indicate a fall in the nitrogen at night, do so only because in 
the samples examined the loss of nitrogen happens to have been greater 
than that of sugars, &c. 
Pigorini’s (10) results for the mulberry, with samples picked at 5 p.m. 
September 7 and 5 a.m. the following morning, show a fall at night by 
Methods B and C, whilst those of the present author (Chibnall (2) ), for 
Phaseolus vulgaris var. multiflorus , for samples picked 8.30 p.m. July 3 
and 2.15 a.m. July 4, each consisting of all the leaves from 12 plants, show 
a rise by Method B, and a fall by Method C. 
Reviewed as a whole the results quoted above undoubtedly establish 
the fact that in general there is a withdrawal of nitrogen from the leaves at 
night. Schulze and Schiitz show that for trees the amount decreases as the 
leaf ages, but, though one would expect the same for annuals, no evidence 
has yet been presented. 
Literature cited. 
1 . Brown, H. T., and Morris, G. H. : A Contribution to the Chemistry and Physiology of Foliage 
Leaves. Journ. Chem. Soc., 1893, lxiii. 604-83. 
2 . Chip.nall, A. C. : Investigations on the Nitrogenous Metabolism of the Higher Plants. II. The 
Distribution of Nitrogen in the Leaves of the Runner Bean. Biochem. Journ., 1922, xvi. 
344-62. 
3 . Czapek, F. : Biochemie der Pflanzen, vol. ii, 1920. 
4 . Davis, W. A., Daish, A. J.,and Sawyer, G. C. : Studies of the Formation and Translocation 
of Carbohydrates in Plants. I. The Carbohydrates of the Marigold Leaf. Journ. Agric. 
Sci., 1916, vii. 255-326. 
5 . Knight, R. C. : P'urther Observations on the Transpiration, Stomata, Leaf Water-content, and 
Wilting of Plants. Ann. Bot., 1922, cxliii. 361-83. 
