126 POPULAB EEEOES. 



says: "A remarkable fact respecting the Ash, 

 which seems to show that the secretions of its leaves 

 are injurious to other plants, is that its drip — that 

 is, the rain that drops from its branches, — renders 

 the ground unproductive around it." 



Without better evidence than is yet afforded it is 

 impossible to accept these explanations to account 

 for the injurious influence of the walnut, ash and 

 certain other plants on surrounding vegetation. 

 The supposition that the injury is caused by poison- 

 ous excretions or exhalations from their leaves is 

 wholly unfounded. We must believe the cause of 

 this injury in all cases to be the same as that by 

 which buckwheat, hemp and other strong and 

 rapidly growing plants are able to free the land 

 from weeds and other vegetation, namely, the pro- 

 duction of shade, and the extraction of moisture 

 from the soil. 



