THE EXCEETOEX THEORY. 128 



fluid in. small amount from their growing roots, but 

 that this fluid instead of being waste material 

 thrown off from the plant is evidently for the pur- 

 pose of dissolving the food materials in the soil to 

 prepare them for absorption by the plant. Even 

 glass may be sensibly eaten away by this fluid 

 exuded by delicate rootlets growing upon its sur- 

 face. 



