The Woburn Pot-Culture Experiments, 1914. 309 

 Table I. — Copper Salts on Wheat, 1914. 



As already observed, the crops were very much larger than 

 in 1913 owing to a richer soil having been used. 



Generally speaking, while the influence of the copper salts 

 was exerted much in the same direction as in 1913, it was not 

 of so marked a nature. This, more or less accidental, repetition 

 of the experiment with a different soil would appear to have 

 a considerable bearing on the conclusions which are to be 

 formed from such experiments as these with regard to the 

 exact amount of particular salts which may prove to be 

 injurious or the reverse. It would seem that it must not be 

 concluded that because in the case of one soil — say a poor one 

 — a certain amount of copper or other body has been found to 

 be harmful, this same amount will necessarily be found to be 

 harmful in the case of a better and richer soil. There can be 

 little doubt that, as the conditions for the vigorous life of a 

 plant are improved, so it is likely to be more immune to 

 injurious influences, and vice-versa. This is, to my mind, the 

 explanation of the quantitative differences between the results 

 of 1913 and 1914. 



Turning to Table I., and comparing this with Table II. of 

 1913 (Journal R.A.S.E., Vol. 74, page 416), it will be seen that, 



