INJURY BY DISINFECTANTS TO SEEDS AND ROOTS. 33 



negative results with the potassium nitrate and iodin test outlined 

 by Loew x 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. 



