58 AGRICULTURAL RESEARCH AND THE FARMER : 



These results have so far been obtained for one season only^ 

 and need confirmation. Further trials on the same hues will be 

 carried out this year, and, if possible, they will be supplemented 

 by actual analysis of different parts of the trees. Recent American 

 work has shown the close connection between the food reserves 

 in the tree and fruit bud formation, and it is evident that investi- 

 gations in these directions will lead to knowledge on which can 

 be based methods of manuring, pruning, and other cultural 

 forms of practice founded on sound scientific principles. 



The results just recorded appear to have significance in con- 

 nection with the peculiar complaint of fruit trees known as " leaf 

 scorch," now being investigated at Long Ashton. This affects 

 orchards largely on certain soils, where for reasons hitherto 

 unexplained the leaves develop a bfown dried margin which 

 gradually extends until the whole leaf may die. This occurs 

 normally in early summer. In bad cases the tree may be prac- 

 tically defoliated, thus seriously affecting the food supply for the 

 following year's crop, and the general health of the tree. The 

 disease is not caused by an insect or fungus pest, but may be 

 associated with an extreme of the " unstable " midsummer 

 condition referred to in the preceding paragraph. It is found 

 that many " scorching " soils have one feature in common — 

 that in the drier period of the season the water supply tends to 

 be relatively deficient as compared with non-scorching soils. 

 Further, the root systems of trees on " scorching " soils are 

 usually of a distinctly inferior character, in that the roots are 

 not well developed and there is a relatively small amount of 

 fibrous root. Thus in summer, when transpiration is most active, 

 the tendency will be for the water supply to the leaf to be seriously 

 reduced, a condition which seems to favour the initial stages of 

 " scorching." We have seen that it is about this time that 

 root development begins to slow down in relation to shoot develop- 

 ment. In the second half of the summer, in " scorched " trees, 

 there is a new leaf development; this corresponds to the time 

 when — as shown in the experiments — root development has 

 again become active. Thus the results obtained in the experi- 

 ments seem to be strikingly co-ordinated with the observed facts 

 regarding "leaf scorch." (Experiments on " leaf scorch" are 

 also referred to on page 63.) 



Treatment of the Tree. 



So far this record of the work of the Stations has taken 

 account only of those questions directly concerned with root 

 action, and the underlying suggestion that the vigour of growth 



