272 SCIENCE AND FRUIT GROWING 



are other effects for which no numerical expression can be found, 

 and these are even more eloquent of the action to those who 

 have the results continually before their eyes : they consist in 

 the effect on the colouring matter in the trees. The pale, sickly 

 green of the leaves of grass-affected trees in early summer is 

 very noticeable, and is quite unlike the changes produced by 

 drought, leaf-scorch, or other affections ; whilst, in the autumn, 

 the grass-effect is still more marked, the autumn tints coming 

 on whilst trees in tilled ground are still quite green, and the 

 fall of the leaf occurring two or three weeks before its usual time. 

 The colouring matter of the bark is equally affected, the. stems 

 and branches becoming light coloured and sickly in appearance, 

 or cedematous, as it has been aptly described. The effect on the 

 colour of the fruit is even greater : where the apple is inclined 

 to be yellow, it becomes much lighter and waxy in appearance, 

 but where it is naturally green, this gives place largely to red, 

 producing a highly coloured fruit (II, 108; III, 48). This effect 

 is well known, and it enhances the market value of fruit from 

 grass-grown trees ; but it would be advantageous to the grower 

 only in the case where the action of the grass could be limited, 

 so as not to materially reduce the total crop or the size of the 

 fruits ; a limitation which it would be difficult to fix at will. 



A limited action of grass on fruit trees may result in advantage 

 to the grow r er, not only as regards the colour of the fruit, but as to 

 the total weight of the fruit borne, for the first effect of a reduc- 

 tion in the vigour of the tree is to make it bear heavily, and 

 it is only when the reduction exceeds a certain value that, the 

 crops are adversely affected. 1 For this reason it is necessary to 

 be careful in interpreting results based on measurements of crops. 

 The limited action of grass on apple trees is illustrated by 

 some of the results at Wo burn, where trees grown in tilled ground 

 have grass either on one or on both sides of them, and at a 

 distance of 5j feet from their stems. Instead of the crops being 

 reduced to almost nil, as was the case with the fully grassed 

 trees, those with one grassed plot near them showed, during 

 the first ten years, an excess of 98 per cent, over the crop from 

 trees quite free from grass, and those with a grassed plot on 

 either side, an excess of 138 per cent. (V, 118; XIII, 10). It 

 was only four or five years after the planting that the effect of 

 the grass near these plots became evident (III, 48), and it is 

 very remarkable how small the proportion of the roots in the 



1 In Wayne Co., New York, tilled orchards gave a crop 80 per cent, 

 higher than those under grass. Jour. Board of Agric., 1905, XII. 557. 



