The Growth of Lemna Plants in Mineral Solutions 
and in their Natural Medium. 
BY 
W. B. BOTTOMLEY, M.A., Ph.D. 
Professor of Botany at King's College , London. 
A CONSIDER ABLE amount of research has been carried out by the 
author during the past few years, on the growth of water plants, chiefly 
Lemna minor , in culture solutions. The results of some of this research 
have already been published, 1 and the work indicates that these plants are 
unable to maintain their normal health and vigour in solutions containing 
only mineral salts, while when supplied with small quantities of organic 
substances they rapidly increase in number, remaining at the same time 
perfectly healthy. Further experiments, which have recently been pub- 
lished, 2 on the beneficial effect of nucleic acid derivatives, which the author 
has found can be extracted from raw peat, 3 and of the products of nitrogen- 
fixing organisms, show that it is the organic matter of these additions which 
brings about the increase in growth, since the ash of the substances has no 
effect on either the rate of growth or the health of the plants. 
Comparison of Different Nutrient Solutions. 
There was the possibility, however, that the failure of these plants to 
maintain a rapid rate of multiplication and their normal healthy appearance 
in the control series of the experiments already recorded might be due to 
an unsuitable combination or proportion of the mineral substances in the 
nutrient solution employed. Throughout the experiments the solution used 
was that advocated by Detmer-Moor, 4 containing — 
Potassium nitrate, 7 grm. 
Di-potassium phosphate, 1*5 grm. 
Magnesium sulphate, 1-5 grm. 
Sodium chloride, 1-5 grm. 
Ferric chloride — a few drops. 
Calcium sulphate in excess (5 grm. were used). 
Distilled water, 3,000 c.c. 
1 Bottomley, W. B. : Proc. Roy. Soc., B, vol. Ixxxix, 1917, pp. 481-507. 
2 Ibid., vol. xci, 1919, pp. 83-95. 
3 Ibid., vol. xc, 1917, pp. 39-44. 
4 Detmer-Moor: Practical Plant Physiology, London, 1898, p. 85. 
[Annals of Botany, Vol. XXXIV. No. CXXXV. July, 1920.] 
