1908.] 



NATURAL SCIENCES OF PHILADELPHIA, 



Table XVI. 



439 



This experiment suggests some results reported by Dandino ('04) 

 on the effect of toxic sohitions on germinating peas and corn. In 

 toxic solutions (dilute acids) the addition of quartz sand (washed in 

 HCl and distilled water) was 32 times as toxic as that without the 

 sand. The author explains this fact as the result of surface action. 

 In the present work experiments with quartz sand and even with 

 pebbles caused an increase in the rate of growth. This is an effect 



