502 



JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



perhaps, not for some time in the actual number of fruits produced), and 

 general ill-health. The trees will be neither things of beauty nor capable 

 of yielding profitable crops. 



A further source of damage to the tree may arise from the fact that 

 when the first foliage is destroyed early in the season the terminal buds 

 of the shoot may be induced to grow out instead of going to rest at the 

 normal time. This extra growth entails a further call upon the reserves 

 laid by, and must be detrimental to the general well-being of the tree. 

 Further, the growth made will probably be made too late to ripen properly, 

 and the foliage near the tips of the shoots will persist for a considerable 

 time after the greater part has fallen. In the present season many leaves 

 were to be seen on such shoots at Christmas. 



The Cause of the Attach. — It will be instructive, first, to see how far 

 the suggestions put forward by different growers as to the cause of the 

 spotting are upheld by actual facts. 



The use of spray fluids too strong for the foliage to bear, may be at 

 once dismissed ; for the trouble appeared both on trees that had been 

 sprayed with such sprays as quassia and soft soap, or with paraffin 

 emulsion against the attacks of aphides, &c, and on those that had not 

 been sprayed ; not only in different plantations, but in the same plantation 

 where one portion had been sprayed and another had not, trees in both 

 were attacked indiscriminately. 



In the same way the appearance of these spots on the leaves cannot 

 be laid to the charge of insects, as these pests were frequently entirely 

 absent from the plants showing the leaf spotting. 



There remains the question of the prevalence of adverse weather 

 conditions. 



Usually an examination into the truth or falsity of accusations 

 against the weather is very difficult to make. Temperature and the 

 other factors that go to make climate often vary materially within 

 the space of even a few hundred yards,* so that no reasoning from the 

 temperature recorded a short distance away from the place where the 

 injury to plant growth has occurred can be accepted without some 

 shadow of suspicion. Fortunately, however, thanks to the well-equipped 

 meteorological station in the Wisley Garden, and the extreme care and 

 accuracy with which the records are kept, the difficulty is in this case 

 reduced to a minimum. 



The apples over the whole of the fruit plantation at Wisley suffered 

 severely, and as the meteorological station stands in the midst of the 

 apple trees, and practically on a level with the whole of the plantation, 

 exact comparisons of the temperatures at certain periods, and the amount 

 of injury done, may be made with a close approximation to the drawing 

 of just inferences. 



The climatic conditions which appear capable of causing the death of 

 certain portions of leaves of such a hardy tree as the apple, so that spots 

 somewhat similar to those described above are produced, while other 

 portions of the leaves remain healthy and green, are : (1) the occurrence 

 of frosts, or (2) temperatures closely approaching freezing-point, and 



* For instance, two thermometers placed about 350 yards apart in different parts 

 of the Wisley Garden often record minimum temperatures varying from 8° to 10°. 



