233 



notice statements of the presence of such insoluble compounds as arsen- 

 ite of iron in solution. These facts ar^ue against the possibility of ac- 

 cumulation of sufficient arsenic in the soil by regular applications of 

 Paris-green in the quantities recommended for the destruction of the 

 Colorado potato-beetle. When rotation of crops is observed and appli- 

 cation of the poison cannot therefore take place upon the same plot more 

 than once in three or four years, it is probable that each application, 

 being acted upon by the natural solvents in the soil, will be removed by 

 drainage before another is made. And yet, even when annual applica- 

 tions are made, so much time must elaj^se before the limit could be at- 

 tained that no injury need be feared from this cause. 



Now, can arsenic be absorbed and assimilated by the i^lant in the 

 economy Q.f growth? My investigations give a negative reply. All 

 of the plants grown, from the largest to the smallest, were examined by 

 careful application of Marsh's test ', yet I failed in any case to detect the 

 presence of arsenic. 



Before making the test the organic matter of the plant was destroyed 

 by boiling it in hydrochloric acid with addition of potassic chlorate, and 

 the solution filtered. 



I also carefully examined potatoes which had been subjected to appli- 

 cations of Paris green, and which were furnished by Mr. George W. 

 Campbell, Delaware, Ohio, Mr. D. C. Richmond, Sandusky, Ohio, and 

 Mr. J. S. Nixon, of Chambersburgh, Pa., and failed in any case to detect 

 the presence of arsenic. 



With these facts before us, and without considering what might be 

 the result of a series of experiments continued through a number of 

 years, we must conclude that plants have not the power to absorb and 

 assimilate from the soil compounds of arsenic, and that though arsen- 

 ical compounds exert an injurious influence upon vegetation, yet this 

 is without effect until the quantity present reaches : for Paris green 

 about 900 pounds per acre ; for arsenite of potassa, about 400 • pounds 

 per acre ; for arseuiate of potassa, about 150 pounds per acre. 



Hastening germination. — M. Heckel has made some experiments 

 in the germination of seeds, in order to notice the effect of different 

 chemical compounds. He placed the seeds between sheets of blotting- 

 pad, and treated them with the several compounds, as follows : 



1. He sprinkled one-half grain of finely-pulverized camphor between 

 the sheets. 



2. Bromide of camphor one-half grain, in the same condition and a 

 similar manner. 



3. •One-half grain bromine water, and an equal quantity of pulver- 

 ized camphor. 



4. Bromine water alone. 



5. Bromide of potassium, finely pulverized. 



6. Chlorine water. 



7. Solution of iodine. 



Under normal conditions, seven to eight days were required for ger- 

 mination. With the application of the different substances named, the 

 time of germination was as follows : Bromide of camphor, 36 hours ; 

 camphor, 4 to 5 days ; camphor and bromine water, first time, 30 hours ; 

 second time, 26 hours ; third time, 30 hours ; bromide of potassium, no 

 effect; iodine, 5 days; bromine, 3 days; chlorine, 2 days. 



Since the effect of bromide of camphor is so much more marked than 

 that of either of its constituents acting singly, it is evident that in its 

 action it suffers no decomposition. It should further be remembered 



