NOTES AND QUERIES. Ill 



is noted. In some soils where the effect produced is not great, 

 grass might be advantageous from a commercial point of view, 

 for the check given to the growth of the tree tends to increase 

 its cropping, and grass affects the colouring matter of all parts 

 of the tree, generally resulting in a high colouring of the fruit. 



The authors are of opinion that forest trees are affected by 

 grass in the same way as fruit trees, when the grass is 

 sown immediately after planting. The only difference between 

 their behaviour and that of the fruit trees was, that in the case 

 of conifers planted in light soil, the effect was much less than 

 with other trees, and some recovery occurred with them as 

 time went on, instead of the effect becoming intensified. 



Much experimental work has been carried out as to the 

 cause of the deleterious effect of the grass. In particular, the 

 action of grass as regards the aeration of the soil, and its effect 

 on soil-moisture, food supply, and on the mechanical condition 

 of the soil, were investigated but with negative results. 

 Similarly the investigation of the bacterial conditions gave 

 no help in the problem. Finally, it was concluded that the 

 grass secretes a toxic substance during its growth, and a 

 considerable amount of positive evidence is brought forward 

 in support of this view. The experiments were carried out with 

 trees growing in pots. It was found that such trees, when 

 watered with the leachings obtained from trays containing 

 grass growing in sand, flourished more than when water alone 

 was supplied ; but when the trays were placed on the surface 

 of the soil (or sand) in which the trees were growing, so that 

 the washings from the grass reached the tree-roots with 

 practically no exposure to the air, they then had a very 

 deleterious effect, nearly, if not quite, as great as when the grass 

 was grown above the roots of the trees in the ordinary way. 

 The trays containing the grass were movable, and the sand 

 in them, with the grass growing in it, was separated from the 

 medium in which the trees were growing by the perforated iron 

 bottoms of the trays and by a sheet of wire gauze ; moreover, the 

 contact between the bottoms of the trays and the sand or soil 

 beneath would be, at the best, very imperfect, so that it is 

 impossible to explain the action of grass in such a case by the 

 abstraction by the grass of anything from the soil (or sand) 

 below the trays, and it must be due to the passage of something 

 from the trays down to the trees. The experiments on this 



