267 
Brenchley .— Organic Plant Poisons . //. 
killed earlier than with 0- or ^-cresol, the survivors with this strength of 
/-cresol were the only plants that had formed even apologies for laterals in 
the presence of this amount of poison. 
The greater toxicity of /-cresol was far more evident with the next con¬ 
centration, M/100 x 1/5 2 . The plants started off all right, but very soon both 
shoots and roots began to fall behind in development. The laterals were 
at first short, curled, and few in number, and the roots remained poor to the 
end, and were also hampered by a strong growth of mould. The shoots 
were variable, some inclined to be flaccid, and all of a sickly green colour. 
The dry weights of these plants were far below those with the other cresols, 
as is shown in Fig. 8. With both 0- and m -cresol the ultimate growth of 
most of the plants was very similar, but the course of development was 
rather different. With 0-cresol growth was like that of the controls for 
about a fortnight, and the shoots continued to keep pace all the way 
through. The roots, however, became very yellow, bunchy, short, and not 
at all like the controls in type. This phase lasted for about a fortnight, and 
then the laterals began to elongate once more. The roots remained some¬ 
what abnormal, being brownish and short at the time of cutting. With 
7/z-cresol again, the shoots were much like those of the controls all the way 
through. The roots formed plenty of laterals, but almost from the 
beginning they were rather short, thin, and of an unhealthy yellowish 
colour. The roots soon became bunchy and the colour deepened. Eventually 
the laterals elongated and the roots improved rapidly, approaching the 
normal more closely; but the final development of the plants was rather 
variable, some making a good recovery, comparing closely with the controls, 
others remaining weaker though much stronger than those in /-cresol. 
With the next concentration, M/ioox 1/5 3 , the differences in the action 
of the various poisons had almost disappeared. The plants with <?-cresol were 
similar to the controls from beginning to end, without any abnormality in 
development. With m- and /-cresol some trace of poisoning was still 
evident; with the former some of the laterals tended to be rather thin and 
of an unusual type, with numerous thin side shoots ; while with the latter some 
of the roots had flabby tips at the first, though lateral formation was normal. 
All plants pulled up well later on, and the dry weights in all three sets were 
very similar. Below this strength the action of the poison could not be 
discerned in any case, all plants comparing well with, controls. 
On the whole, it may be said that /-cresol is more toxic in high con¬ 
centration than o- or ^-cresol, and that probably /^-cresol is slightly more 
poisonous than 0-cresol, though the difference is not well marked. The 
apparent anomaly exists, that in spite of this absolute range of toxicity the 
highest concentration of 0-cresol (the least poisonous) kills all the plants 
outright, whereas the same strength of /-cresol (the most poisonous) allows 
the plants to make a little growth, and also to attempt to put forth laterals, 
which was not the case with 0- or 7^-cresol. 
