578 Brenchley .— The Influence of Copper Sulphate and 
To sum up, it appears that copper, as sulphate, does not exert a stimu¬ 
lative action on barley, however small the concentration, but that the toxic 
effect of the salt gradually decreases with the concentration, until strengths 
of i : 5,000,000 and under have no appreciable effect, either toxic or 
stimulant, upon the growth of the plant. 
Manganese Sulphate. 
The effect of Manganese on plant growth has recently been attracting 
considerable attention, and much work has been reported on the subject. 
Manganese occupies a different position from copper, for while the latter is 
a definite poison, the former is not, and minute traces of it are found in the 
ash of almost all plants. Manganese salts in sufficient concentration are 
well known to exert a toxic influence upon plant growth, and the tendency 
has been to assume that sufficiently dilute strengths of the salt have a con¬ 
sistently stimulative effect upon growth. Several investigators, notably 
M. Bertrand and some of the Japanese scientists, have reported results 
in support of this view, but nearly all the work has dealt with the action of 
manganese salts on plants growing in soil, either in pots or in the open field. 
This at once introduces a point of difficulty, as it is impossible to determine 
how far the results obtained are due to the direct action of the manganese 
salts themselves on the plants, or how far interaction has taken place 
between the manganese salts and the soil, thereby influencing the growth of 
the vegetation. Also, manganese is frequently an element contained in the 
soil, so one cannot be certain what concentrations of salts are really being 
dealt with. 
In order to eliminate, as far as possible, this element of uncertainty due 
to unknown external factors, experiments with water-cultures have been 
made at Rothamsted. The initial series of plants, in 1908, were carried 
right through from seed to seed, as the barley plants were allowed to grow 
till they had set and ripened the grain in the ear. Barley grains of an abso¬ 
lutely pure strain were graded, only varying between 0*04 and 0*06 gram. 
These grains were germinated in damp sawdust as usual, and were then 
watered with dilute food solution to promote growth. As soon as the seed¬ 
lings were large enough they were transferred on March 7 to bottles 
containing the following nutritive solution with the addition of manganese 
sulphate (= MnSo 4 . 5 H 2 0 . = M.S.) in concentrations varying from 1: 10,000 
to 1 : 1,000,000,000, with a control containing no M.S. 
Potassium Nitrate ... 0-5 gm. Sodium Chloride . . . o*i gm. 
Potassium Phosphate . . 0-25 „ Ferric Chloride . . . Trace. 
Magnesium Sulphate . . 0*25 ,, Water.1,000 c.c. 
Calcium Sulphate . . . 0*25 ,, 
Five similar sets were grown to put a check on individuality. As 
ordinary ferric chloride usually contains a certain small percentage of 
