February, '10] entomologists' discussion 35 



spraying. Now nearly all, if not all, of these marls contain arsenic, 

 but in small quantities compared with the surface soils. These things, 

 apparently, all work together to produce the effects described, but 

 neither the marl nor the arsenic in the marly soils can be blamed 

 for the arsenic in the trees and the fruit, for this is a very widespread 

 condition. I have examined fruit from the following states: Cali- 

 fornia, Colorado, Michigan, New York, Illinois, Ohio and Pennsyl- 

 vania and uniformly found arsenic. No one, however, need to 

 be alarmed about the amount of arsenic present being in the least 

 dangerous, for they would scarcely obtain an ordinary medicinal dose 

 if they ate ten pounds of apples a day. Arsenic, however, can be 

 detected in the urine of parties eating very freely of such apples. I 

 will, however, reserve this subject for discussion elsewhere. 



Mr. Headden exhibited samples of roots which had been injured 

 by arsenical poisoning, as well as small tubes showing the results of 

 analysis of fruit trees from various sections of the country, and one 

 of these tubes contained a mirror Avhich had resulted from the analy- 

 sis of an elm tree that contained a considerable amount of arsenic. 



Member : I would like to ask whether Doctor Headden has noticed 

 any connection between the appearance of arsenical poisoning and 

 the amount of moisture. Is it more likely to appear in a tree stand- 

 ing in dry or wet soil ? 



Mr. Headden : Colorado orchards are irrigated, and it is possible 

 that the arsenic is carried do^^Ti to the roots sooner with us than where 

 the soil is not treated in this way. Nevertheless, analyses have shown 

 that sick trees on almost all kinds of soil showed the presence of 

 arsenic in considerable quantities, if they had been sprayed. 



Mr. Washburn: I would like to inquire how Doctor Headden 

 secures his samples, in order to determine whether the tree is suffer- 

 ing from arsenical poisoning, and how large a piece of bark would be 

 necessary to detect the poison. 



Mr. Headden: I have always endeavored, in taking the samples, 

 to refrain from selecting any of the outer bark of the tree, as this is 

 liable to be covered to some extent with poison, especially trees that 

 have been recently sprayed. 



The wood just below the bark is usually selected for this purpose, 

 but in cases of root injury the woody tissue of the roots is used, but 

 not the bark. 



Mr. Washburn: Is not this fact more striking in alkali soil? I 



