274 SCIENCE AND FRUIT GROWING 



The trees with the grass replaced right up to their stems were, 

 in this case, all killed (XIII, 12). 



Connected with the probable tendency towards recovery of 

 trees from the grass-effect when circumstances are favourable, 

 there is another factor in the case which is of considerable 

 importance both from a practical and theoretical point of view, 

 namely, that a great reduction in the deleterious effect occurs 

 when grassing is effected gradually. Thus, a plot of dwarf 

 Cox's Orange Pippins was laid down to grass immediately after 

 the trees were planted, and, when they were lifted fifteen years 

 later, their weight was found to be only 9 per cent, of that of 

 similar trees grown in tilled soil ; whilst in a neighbouring plot, 

 which had been allowed to become weed-grown from the first, and 

 where the weeds had gradually been ousted by grasses, the trees 

 weighed 30 per cent, of trees in tilled ground, or over three 

 times as much as the trees which had been grassed at once 

 (XIII, 25; see also III, 54). In another experiment wherein 

 standard apple trees were used, the yearly growth, as compared 

 with that of similar trees in tilled ground represented by 100, 

 gave the values shown in the first line below for trees over 

 which the turf had been replaced immediately after planting; 

 whereas others, wherein the turf had been removed to a distance 

 of three feet from the stems, and the cleared area had been 

 allowed to grass itself over gradually, yielded the values set out 

 in the second line. In the latter case no deleterious effect was 

 observed in the first season, and, taking the average of the six 

 succeeding seasons, the growth of these trees had been twice 

 as great as that of those which had been grassed at once. 



Mean. 



1910. 1911. 1912. 1913. 1914. 1915. 1911-15. 

 Turf replaced 76 30 6 5 n 7 12 



Grassed gradually 101 38 12 10 33 28 24 



