The Effect upon the Host-Plant. 233 



show that grapes sprayed intelligently rarely contain more 

 than 5 milligrams (0.005 gram) of copper per kilogram, the 

 average being from 2|- to 3 milligrams per kilogram. In 

 other words, 1,000,000 pounds of grapes sprayed in the usual 

 way with the Bordeaux mixture would contain from 2| to 5 

 pounds of copper. To reduce the figures still further, each 

 1000 pounds of fruit would contain 17.5 to 35 grains of copper. 

 On this basis an adult may eat from 300 to 500 pounds of 

 sprayed grapes per day without fear of ill effects from the 

 copper. This shows how ridiculously absurd are the state- 

 ments that fruits properly sprayed with the Bordeaux mixture 

 or any other copper compound are poisonous." 



The effect of applying soluble arsenic upon foliage has been 

 considered on page 117, but there still remains a point in regard 

 to the injury done by arsenical poisons to animals consuming 

 the grass beneath. Professor Cook has carefully experimented 

 in this direction, and his results are so conclusive that they are 

 here given in full : " In tree No. 1 a thick paper was placed 

 under one-half of a rather small apple tree. The space covered 

 was six by twelve feet, or seventy-two square feet. The paper 

 was left till all dripping ceased. As the day was quite windy, 

 the dripping was rather excessive. In this case every particle 

 of the poison that fell from the tree was caught on the paper. 

 Dr. R. C. Kedzie analyzed the poison and found four-tenths (.4) 

 of a grain [of arsenic]. Tree No. 2 was a large tree with very 

 thick foliage. Underneath this tree was a thick carpet of 

 clover, blue grass, and timothy just in bloom. The space cov- 

 ered by the tree was fully sixteen feet square, or equal to two 

 hundred and fifty-six square feet. As soon as all dripping had 

 ceased, the grass under the tree was all cut very gently and 

 very close to the ground. This was taken to the chemical 

 laboratory and analyzed by Dr. R. C. Kedzie. There were 

 found 2.2 grains of arsenic. Now, as our authorities say that 

 one grain is a poisonous dose for a dog, two for a man, ten for 

 a cow, and twenty for a horse, there would seem to be small 

 danger from pasturing our orchards during and immediately 

 after spraying, especially as no animal would eat the sprayed 

 grass exclusively. To test this fully, I sprayed a large tree 

 over some bright, tender grass and clover. I then cut the 

 clover carefully, close to the ground, and fed it all to my horse. 



