Xew Yokk Ageicultural Experiment Station. 295 



It was pointed out before that crown-rot occurs both in sprayed 

 orchards and in those which had never been sprayed; that arsenic is a 

 normal constituent of the soil and often occurs in fairly large quan- 

 tities and is therefore taken up by plants. Attention was also called 

 to the fact that herbaceous plants grow about crown-rotted trees, as 

 is even shown in some photographs used by Headden. Ball and his 

 associates^ have more recently shown that large quantities of arsenicals 

 used in spray mixtures may be allowed to stand in contact with the 

 bark of apple trees and be poured about their roots without resulting 

 in harmful effects in one season. On the other hand Swingle and 

 Morris^ have found that some arsenic compounds are more or less 

 injurious when held in contact with wounded bark of apple-tree 

 branches for some time. But some of their methods are objection- 

 able because the excessive moisture and lack of proper aeration may 

 induce hyperplastic growths and thus admit solutions which probably 

 could not have penetrated the normal cork layers of the bark. 



When plants absorb salts containing a poisonous element they are 

 not necessarily injured; especially is that true of trees where so much 

 of the unessential matter absorbed is stored in the non-living cells of 

 the wood. For example, copper is one of the most active plant poisons 

 known, so deadly in fact that it is not advisable to use water distilled 

 from copper vessels when making culture solutions, yet copper is 

 absorbed in the soil solution by plants and may even be stored in 

 enormous quantities. In the vicinity of an abandoned copper mine 

 Lehman^ found that herbaceous plants contained from 83.3 to 560 mg. 

 of metallic copper per kilogram of dry weight, while the different 

 parts of a nearby cherry tree contained from 8.75 to 112.5 mg. per 

 kilogram of dry weight. 



MacDougal* also notes the presence of large quantities of metallic 

 copper in wood and other cells of Quercus macrocarpa. 



The chief evidence that has been advanced to show that arsenic 

 causes crown- rot is the fact of its presence in such trees. But as 

 arsenic is also present in normal trees and other vegetation that 

 evidence is worthless; especially when it is borne in mind that 

 trees may store large quantities of poisonous substances without 

 being injured. 



^ E. D. Ball, E. G. Titus, and J. E. Greaves. The season's work on arsenical poison- 

 ing of fruit trees. 



Jour. Econ. Ent. 3:187-97. 1910. 

 - D. B. Swingle and H. E. Morris. A preliminary report on the effects of arsenical 

 compounds upon apple trees. 



Phytopath. 1:79-93. 1911. 

 ^ K. B. Lehman. Der Kupfergehalt von Pflanzen und Thieren in kupferreichen 

 Gegenden. 



Arch. Hyg. 27:1-17. 1896. 

 * D. T. MacDougal. Copper in plants. 

 Bot. Gaz. 27:68-69. 1899. 



