INJURY BY DISINFECTANTS TO SEEDS AND ROOTS. 33 
negative results with the potassium nitrate and iodin test outlined 
by Loew ' and turning blue litmus red, the latter phenomenon 
likely indicating absorption rather than acid reaction for either 
soil. 2 Titration of extracts from fresh samples of these soils should 
give more indication of the real cause of the different behavior of 
acid at the two places. If difference in reaction of the two soils 
explains the different results, it is probable that the difference in 
capacity for disinfectants would be less marked or even reversed with 
such disinfectants as copper sulphate. 
Further evidence of the failure of chemical analysis or physical 
characters to show what action disinfectants will have on roots in 
different soils is seen in the difference between the results in these 
nursery soils and the results obtained by Lipman and Wilson 3 with 
a soil described as sandy and having a chemical constitution showing 
no very radical differences from those reported in the foregoing. 
On this soil they found that there was no evidence of damage to 
either wheat or vetch seedlings by sulphuric acid in the amount of 
600 parts per million of water-free soil applied several days before 
sowing. While these experiments, conducted in pots, can not be 
directly compared with those of the writer, it is sufficiently evident 
that the results are very different. At Halsey, 0.125 fluid ounce 
per square foot, followed by the ordinary watering given germinating 
seed beds, entirely prevented the growth for at least a month after 
application of the monocotyledonous and dicotyledonous weeds rep- 
resented in the seed beds. Assigning to the commercial acid used 
a maximum strength, which may be assumed as having a specific 
gravity of 1 .84 and purity of 95 per cent, and to the soil a minimum 
weight, which for this fine sand may be taken as SO pounds per cubic 
foot, we find that even if all the acid applied were held in the upper 
4 inches of soil the weight of H 2 S0 4 used was only 534 parts per mil- 
lion of soil. That this treatment should have prevented all growth 
of weeds, in which both monocotyledons and dicotyledons were repre- 
sented, while 600 parts did not even decrease the growth rate of 
wheat and vetch on the soil used by Lipman and Wilson, indicates 
a very considerable difference in behavior of acid in the two soils. 
As injury to pines is caused on the Morrisville soil by amounts of 
acid only one-third of that required to injure pines at Halsey, the 
contrast in the results between the Morrisville soil and that used by 
Lipman and Wilson is still more marked. 
The observations made by the writer on the species of Equisetum, 
pines, grasses, and dicotyledons most common in the seed beds at 
1 Loew, Oscar. Studies on acid soils of Porto Rico. Porto Rico Agr. Exp. Sta. Bui. 13, p. 6, 1913. 
2 Cameron, F. K. Op. cit., p. 66. 
3 Lipman, C B., and Wilson, F. H. Toxic inorganic salts and acids as affecting plant growth. In 
Bot. Gaz., v. 55, no. 6, p. 409-420, 1913. 
