INJURY BY DISINFECTANTS TO SEEDS AND ROOTS. 29 



With these salts, as with the acids, the pines appeared on the whole 

 more resistant to toxic action than the angiosperms present. There 

 was less evidence in the experiments of a difference in susceptibility 

 to salts in general between the grasses and the dicotyledons. Heald's 

 tests of the resistance of corn and peas to copper salts 1 showed for 

 these plants a reversal of their relative resistance to acid, the peas 

 being able to grow in twice as strong copper solution as corn, whereas 

 with four mineral acids they could grow in solutions only one-fourth 

 as strong. 



Ammoniacal copper carbonate was also used with jack pine. A 

 plat of this pine was given a solution made up of 0.006 ounce of 

 copper carbonate and 0.099 fluid ounce of ammonia per square foot 

 the first day after germination, and this was repeated two days later. 

 Eight days after germination the plat was again treated, using 0.014 

 ounce of carbonate and 0.22 ounce of ammonia per square foot. 

 Practically all the seedlings were killed by these treatments. Most 

 of the injury appeared to be done by the first two applications, in 

 which a total of 0.012 ounce of carbonate per square foot was ap- 

 plied. This plat, which received a total of 0.026 ounce of copper 

 carbonate, was resown 16 days after the last application. No serious 

 injury occurred to the second sowing. 



Another plat treated just before sowing (plat 60, Table VI) fur- 

 ther indicated a very great toxicity for ammoniacal copper carbonate 

 if only the amount of copper contained is considered. The injury 

 to pine in this plat was much more severe than in plat 64, which had 

 been treated with sulphuric acid more than 25 times the weight of 

 the copper carbonate used on plat 60. It is probable that the 

 extremely toxic action of this fungicide was due more to the action of 

 the ammonia than to the copper. The known tendency of ammonia 

 to prevent the precipitation of copper salts from solution may, how- 

 ever, result in more prolonged activity of the copper in this disin- 

 fectant than when simple aqueous solutions of copper salts are applied 

 to the soil. 



FORMALIN. 



Like mercuric chlorid, formalin is capable of killing seed outright 

 if applied at the time of sowing. In a test of yellow pine in which 

 the disinfectant was applied at sowing (plat 415, Table VI) most of 

 the seeds were killed before they gave any outward evidence of 

 commencing to germinate. So far as could be learned, those which 

 were able to start germination were uninjured. In plat 416 (Table 

 VI), which received the same amount of formalin, half at the time 

 of sowing and half at an interval of a month earlier, no injury could 

 be detected. In all other cases, formalin was applied several days 



i Heald, F. D. Op. cit, p. 152. 



