EXPERIMENTS CONDUCTED WITH A VIEW TO CONTROLLING DISEASE. 53 



so that the non-bearing is not due to the nature of the stock. In 1915 the Blenheim Orange which has 

 fruited was the most luxuriant-growing tree in the screen, and this season it still maintains its 

 superiority. 



RELATIVE SIZE OF THE TREES. 



The most luxuriant-growing tree in 1915 was considered to be Blenheim Orange on Spy (No. 4), 

 which, however, bore no fruit. In 1916 four trees were selected of the same age and apparently 

 similar in growth, all of which bore a small amount of fruit, with the exception of French Crab. 



It is no easy matter to determine accurately the size of a growing tree, since there are so many 

 factors entering into the calculation which cannot be properly estimated. I have, however, taken as 

 a basis the three principal factors of the girth of the stem, the height of the tree, and the spread of 

 the branches, and by taking the mean of these three measurements an approximate result is obtained. 



Applying this test to the four trees selected, the following table gives the results as determined on 

 1st June : 



TABLE XXX. 



MEASUREMENT OF HEIGHT OF TREE. SPREAD OF BRANCHES. AND GIRTH OF STEM. 



No. Variety. Stock. Height. Spread. Girth. Mean. 



4 Blenheim Orange Spy (108 ins.) 100 (90 ins.) 100 (8 ins.) 100 100 



50 French Crab Spy (108 ins.) 100 (53 ins.) 59 (7} ins.) 94 84 



22 Cleopatra Cole's Paradise (108 ins.) 100 (63 ins.) 70 (5? ins.) 70 80 



27 Cleopatra Winter Majetin (102 ins.) 94 (46-i ins.) 52 (6^ ins.) 77 74 



The Blenheim Orange is taken as the standard, because the three measurements are highest in 

 this variety, and the actual measurements in inches are given in brackets. It will be seen in future 

 years which of these varieties shows the greatest variation and whether the increase in size is most 

 marked in height or spread of tree or diameter of stem. 



(3) CLEOPATRA BUDDED AND GRAFTED ON TO PEAR STOCK. The object of this experiment is 

 to test practically whether a stock non-liable to Bitter Pit will influence the scion of a susceptible 

 variety so that it will produce fruit free from the disease. There is a difficulty in getting a blight- 

 proof and non-susceptible variety of apple, and since the pear is generally free from the disease in the 

 Burnley Horticultural Gardens, it was chosen as a stock. 



There are two top-grafted trees of Cleopatra, grafted in September, 1914, and planted out in 

 July, 1915, one of which is much superior to the other. The tree which has made the poorest growth, 

 has produced one fruit, and when examined fully half -grown there was no external sign of Pit. When 

 ready for picking in March, however, four pits had developed on one side. 



Only one Cleopatra, budded on to a seedling pear in February, 1914, grew, and made but poor 

 growth. However, it has produced one fruit, which developed one pit. In the early stages of growth 

 at least, a stock which is non-liable does not confer immunity on the scion of a susceptible variety, 

 whether budded or grafted (Fig. 69). 



(4) VARIETIES ON THEIR OWN ROOTS. The three varieties of Gravenstein, Magg's Seedling, and 

 Winter Majetin were planted out on their own roots on 13th July, 1913. The Northern Spy has now 

 been added to the list for comparison, since it is almost universally used as a stock, and was planted 

 out in July, 1916. 



The object of this experiment is mainly to test the assertion so frequently made that varieties 

 grown on their own roots are free from Bitter Pit. 



Gravenstein. There are six trees of this variety, and the growth is fairly equal throughout. 

 They have all made satisfactory growth, and reached an average height of 3^ feet three years from 

 planting. 



