262 POPULAR SCIENCE MONTHLY 



Agricultural Society of England for the past few years contain a series 

 of significant articles by the Duke of Bedford and Dr. Pickering upon 

 the mutual effect of plants upon each other. These authors observed 

 that the growth of young apple and pear trees was severely retarded 

 when grass was allowed to grow about their roots. The harmful effects 

 were much more pronounced in the case of grass than in the case of 

 weeds. Young trees planted in a pasture, with all the sod replaced 

 around them, died during the first season, but when a small circle of 

 sod was permanently removed, they lived. The first supposition was 

 that the injury was due to the removal of plant nutrients, and experi- 

 ments were accordingly inaugurated to ascertain whether this was the 

 case, but all the experiments answered the question in the negative. 

 Experiments were also conducted to determine whether the removal of 

 water by the grass was the cause of the injury, but again a negative 

 answer was obtained. The results of other experiments showed that 

 the injury could not be ascribed to the presence of an excessive amount 

 of carbon dioxide, or to the lack of oxygen, since the characteristic 

 injury was only observed when grass was growing around the tree roots. 

 The authors finally concluded that the injurious effect of the grass 

 could be due only to some action on the tree roots akin to that of direct 

 poisoning, leaving the question open as to whether this action is due 

 to excretions from the grass or to the changed bacterial action in the 

 soil induced by the presence of grass. 



Jones and Morse, of the Vermont Agricultural Experiment Station, 

 have reported observations which indicate that a somewhat similar 

 antagonism exists between butternut trees and the shrubby cinquefoil. 

 They found that the cinquefoil, which grows abundantly in certain 

 localities, was not found under or around butternut trees on a circle 

 fully twice the diameter of the tree-top. Their observations showed 

 that the " dead line " for the cinquefoil is pushed outward year by 

 year as the butternut tree expands, so that the trees may be surrounded 

 by a circle of dead and dying cinquefoil plants bordering the clean 

 grass plot under the tree. Upon closer examination the roots of dead 

 and dying cinquefoil plants were found always to be in close proximity 

 to. those of the butternut trees. That the injury was not due to shade 

 or the removal of water is very improbable, since other species of 

 deciduous trees in the same locality were closely surrounded by cinque- 

 foil plants. 



The antagonistic effect of roots is also shown by an instructive 

 experiment recently published by Hunt and Gates in a bulletin of the 

 Cornell Agricultural Experiment Station : Rectangular boxes of soil 

 were planted with corn in one end and with common weeds in the 

 opposite end. Where the roots of the two kinds of plants were allowed 

 to intermingle, the corn made less growth than where a partition in 



