HORTICULTURAL RESEARCH 493 



unhealthy in colour, whilst the fruit is evidently lacking in 

 green colouring matter, being either of a waxy yellow tint or 

 showing a strong red coloration. This latter may be an 

 advantage for market purposes and if the action of the grass 

 could be restricted, so as merely to affect the colour of the fruit 

 without seriously stunting the tree, it would be beneficial. 

 This can be done in some cases by having the grass over only 

 a small portion of the roots but the behaviour of different 

 varieties of trees and even of different individuals of the same 

 variety, differs too much to render such a method of culture 

 practicable. 



The Water Supply 



Naturally, the first explanation suggested was that the grass 

 abstracted from the soil the moisture and other food materials 

 required by the tree. Numerous experiments, however, 

 negatived such an explanation. That grass promotes evapora- 

 tion, rendering the soil drier than if the surface be kept tilled, 

 is well known ; but it was found that this drying effect did not 

 become appreciable until somewhat late in the year, whereas 

 the effect of grass on the trees is manifest even in the early 

 spring : moreover, in one season throughout which determina- 

 tions were made, the drying effect of the grass was never 

 so great that the amount of water in the soil was reduced below 

 the optimum amount for vegetation ; and yet the trees were 

 suffering severely. There is also the general consideration that 

 the grass effect is manifest in wet as much as in dry seasons 

 and that trees in tilled ground, even in the driest seasons, 

 do not show the same symptoms as trees suffering from grass. 

 It may further be added that in the original grassed plots at the 

 Fruit Farm, the soil contains actually more moisture than is 

 found in the neighbouring tilled plots : what the explanation of 

 this difference may be is not evident ; but it is clear that the 

 behaviour of the trees in these particular grass plots cannot be 

 due to a diminished water supply. 



Further evidence of this fact was obtained by supplying trees 

 in grassed plots with additional moisture through pipes reaching 

 down to their roots ; it was thus ascertained that the effect of 

 the grass was not overcome even when the soil was kept so that 

 there was more moisture in it than in the neighbouring tilled 

 plots. Similar results have been obtained in other experiments 



