276 Brenchley .— Organic Plant Poisons. II. 
killed the plants immediately, although the shoots grew just a very little 
during the first three days. The leaves soon began to die down from 
the tips and the plants quite shrivelled up within three or four weeks. 
No mould appeared in their case, though with peas such a strong growth 
was observed. 
With M/iooxj- growth was checked at once and for about a fortnight 
little progress of any kind was made. The leaves kept their healthy green 
colour, but the stems became purplish. After the plants had marked time 
for about four weeks the roots began to make slight attempts to put out 
laterals, but the shoots did not respond at once. Lateral formation pro¬ 
ceeded apace and the roots became very full and bunchy, but very few of 
the laterals ever entered the solutions. Only in three plants was the 
reluctance overcome, and in these cases the roots were rather long and 
thick. As a result of this reluctance on the part of the roots the shoots 
were unable to make as much improvement in growth as might have been 
expected, and the ultimate result was that the plants were very variable, so 
that the average dry weight does not in this case convey a true idea of what 
actually happened. 
The toxic effect was still marked with the next strength, M/ioox 1/5 2 , 
as for nearly three weeks the root growth was not much better than it was 
with stronger orcinol. When once lateral formation did make a start, how¬ 
ever, progress was rapid. Thick rootlets were pushed out into the solutions, 
and these were eventually accompanied by more normal thinner roots 
bearing fine laterals. In spite of all the progress the initial check was never 
fully overcome and the average dry weight of the plants was considerably 
behind that of the controls. 
Even with a lower strength of orcinol, M/100 x 1/5 3 , the roots were rather 
adversely affected at first. For a few days this was not evident, but then 
the growth of both roots and shoots fell behind that of the controls, 
although later on most of the leeway was made up. 
An interesting feature of the action of orcinol on barley is that at the 
time of cutting it appeared that there was a decided stimulation with some 
of the concentrations below those discussed above. This appearance, how¬ 
ever, was not borne out by the dry weights, the balance being in favour of 
the control plants. This apparent stimulation was not observed in the case 
of peas. 
Summary of Results. 
1. The general action of the various phenols upon barley and pea 
plants grown in water cultures is very similar, though the individual sub¬ 
stances exercise their specific action at somewhat varying concentrations. 
In every case a solution containing one per cent, of the molecular weight 
(M/100) of the phenol proves to be fatal, and usually death occurs within 
