The Influence of Copper Sulphate and Manganese 
Sulphate upon the Growth of Barley. 
BY 
W. E. BRENCHLEY, B.Sc., F.L.S., 
Rothamsted Experimental Station. 
With Plate XLVII, and four Figures in the Text. 
D URING recent years a great deal of attention has been directed to the 
physiological action of certain chemical substances upon the growth 
of plants, particularly with regard to plant poisons. A theory has been put 
forward that all chemical substances which are deleterious to plant growth 
act universally as stimulative agents if they are only available in exceedingly 
minute quantities. An examination of the literature on the subject indicates 
that many of the experimental results are self-contradictory and that, as 
a general rule, little can be regarded as definitely settled. 
In 1907 investigations were begun at the Rothamsted Laboratory 
to determine, if possible, the limits of concentration of a few specified salts 
necessary to produce either a toxic or stimulative effect upon the growth of 
certain of the higher plants. The experiments were carried on by means 
of water-cultures, as they afford the most ready method of controlling the 
nutrient and toxic substances supplied to the plants. Great care was 
observed to eliminate, as far as was practicable, any disturbance of the 
experimental results by outside causes, such as dirty bottles, corks, &c. 
The plants were grown singly in clear glass bottles fitted with bored corks 
to support the plants. These corks were either new or else were sterilized 
n an autoclave previous to use in order to kill off any adherent mould spores 
or green algal cells. The bottles were filled with culture solution to within 
an inch from the top, and the plants after germination in fresh damp saw¬ 
dust were lightly held in position in the cork by means of non-absorbent 
cotton wool. Great care was taken to keep the latter dry, as damp wool, 
especially in the early stages of growth, would prove a fruitful source of loss 
of plants on account of disease and bacterial action. The bottles were then 
covered with closely fitting brown paper coats to exclude light from the 
solutions and roots. 
[Annals of Bolany, Vol. XXIV. No. XCV. July, 1910.] 
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