26] 
Brenchley.—Organic Plant Poisons. II. 
The plants in strong nutrients continued to grow in a normal way, forming 
laterals within the solutions. Those in weak solutions, on the other hand, 
again formed numerous laterals bunched together above the surface of the 
solutions, which did not proceed to elongate and enter the water for several 
days or a fortnight. It is very noteworthy that, in spite of the striking 
difference in the development of the roots, the ultimate dry weights in each 
case did not fall very much below the weights of the respective controls, 
though far greater differences were shown by the shoots. 
With all concentrations below the last described the growth of the 
plants compared very favourably with that of the controls all the way 
through ; there was no abnormality in development or colour, and the dry 
weights proved to be fairly uniform, giving no signs of stimulation. 
A comparison of the dry-weight curves shows that with every concen¬ 
tration, from the least to the greatest, the growth of the plants in strong 
nutrients was uniformly better than in weak, the curves running fairly 
parallel. The earlier recovery of the roots in strong nutrients is an instance 
of the masking action exercised by food salts on the action of a toxic sub¬ 
stance, as has been seen with inorganic poisons. 1 It is probable that the 
phenol is gradually decomposed by oxidation, thereby getting less in quantity, 
and that the extra energy generated by the more liberal food supply in strong 
nutrients enabled the roots to overcome the inhibiting action before as much 
decomposition had occurred as was necessary with weak nutrients. 
In another series carried out later in the year (Oct. 15 to Jan. 30) with 
strong nutrients the toxicity of the higher concentrations of phenol was 
rather greater than in the previous experiment. This was shown by the 
abnormal and delayed root growth being developed with less poison, and was 
probably due to the fact that the vitality of the plants is lower in the depth 
of winter, so that they had not so much energy to withstand the poison. When 
once a fair start was made, however, the ultimate recovery was quite good. 
An initial series of barley with phenol was grown early in the year— 
March 5 to April 17. M/100 proved instantly fatal. The day after the 
plants were started the roots were very translucent and rapidly became 
flaccid. The shoots kept their green colour for a time without making the 
least growth, but after ten days they turned an unhealthy yellow brown 
colour and rapidly died off. M/ioox-J permitted a little shoot develop¬ 
ment, but no root growth took place for a month, and the roots were 
brownish. By this time the shoots were very small, variable, with the base 
of the stems deep purple-red in colour—a sure sign of starvation, due in this 
case to insufficient nutriment being taken by the roots in the midst of plenty. 
At length the roots began to grow a little ; they became bunchy above the 
solutions without entering, and they maintained this attitude to the end of 
the experiment, refusing to put out long laterals into the solutions. The 
1 Brenchley, W. E.: Inorganic Plant Poisons, 1914, p. 20. 
