INJURY BY DISINFECTANTS TO SEEDS AND ROOTS. 31 
The relative resistance of Finns ponderosa to the acid is probably 
due to its rapid growth, as at Halsey. The severe injury to P. strobus 
is rather surprising in view of the length of time which elapsed before 
germination. The- consistent relation in series 638 between the de- 
crease in stand and the amount of acid used and the evidently helpful 
effect of frequent watering leave no reasonable doubt as to the agency 
of the acid in causing the decreased stand. In all of the series ex- 
cept 631 the treated plats were uniformly poorer than the checks. 
In series 638, fewer seedlings appeared in acid plats than in the 
checks in all cases, the deficiency being greatest in the ordinary 
watering plats, and the amount of death just after the seedlings came 
up in the ordinary watering plats was very large. The amount of 
germination and early loss for the other series was not determined. 
The evidence of the experiments at Morrisville as a whole shows 
that at this nursery the amounts of acid necessary to cause injury 
were much smaller than at Halsey. 
GENERAL DISCUSSION AND CONCLUSION. 
It is evident that the toxicity of disinfectants to the roots of plants 
in soil at Halsey, Nebr., varies greatly in response to a number of 
different factors. The amounts of water in different parts of the 
soil at different times and the movements of soil water, which result 
in concentrating the soil solution at particular points, must be con- 
sidered, as well as the concentration of the solution applied. The 
depth of the root tips in the soil at the time of greatest concentration 
of the soil solution is also of prime importance, and the time of appli- 
cation is a very important variable. 
In general, while it is evident that disinfectants do not act on plant 
roots in soil to the same extent as in liquid cultures, they seem to 
act in much the same way. If only the free poison in the soil solution 
is considered, it is doubtful whether a great difference in degree of 
toxicity can be found in soil and in liquid cultures. However, the 
activity of poisons in the soil solution should not be expected to 
equal their activity in pure water cultures. Antitoxic relations 
which have been found by various workers to exist between numerous 
substances in water cultures may be expected to exist between most 
disinfectants and various components of the soil solution. An in- 
vestigation of antagonism between substances obtained in soil ex- 
tracts and some of the substances used in soil disinfection should 
yield some interesting results. Most poisons are of necessity rather 
unstable substances, and even where leaching is prevented, as in 
pot experiments, and nonvolatile substances are used, the loss of 
free poisons from the soil solution by combination with soil con- 
stituents and by other absorptive processes is undoubtedly great. 
