WINTER PRUNING EXPERIMENTS WITH APPLE TREES. 147 
as compared with considerably under 3 oz. for the fruits of the 
unpruned trees. (Not well shown in figs. 32 and 33.) 
It is interesting to find that two varieties, ' Lord Derby ' and 
' Beauty of Bath,' which in 1919 and 1920 produced slightly larger 
fruits on the unpruned trees, have in 192 1 so far fallen into line 
with the other varieties that the average for the three years is now in 
favour of the long-spur pruned trees. From these and other cases 
it seems reasonable to expect that the difference will be increasingly 
in favour of the long-spur pruned trees as time goes on. 
4. Effect on Biennial Bearing. 
The habit of bearing crops in alternate years, so common among 
trees of certain varieties, is one of the difficulties which the most 
progressive growers are constantly trying to overcome. The ideal 
to aim at would no doubt be to get heavy crops in the years of general 
shortage ; but since the years of glut and shortage do not come alter- 
nately with perfect regularity this is almost too much to hope for. 
But there are already indications that our pruning is tending to check 
this habit, even where, as with ' Newton Wonder,' the tipped and 
spurred trees have borne more fruit than the unpruned trees. 
No satisfactory method of expressing this habit in figures, so far 
as I am aware, has yet been found. A considerable number of possible 
methods have been tried in connexion with our records, but they 
have all been rejected as not allowing for all the facts which must be 
taken into account, and not giving any real comparison between 
groups of trees pruned in different ways. It is necessary, for instance, 
to allow for the fact that each year is for some trees their " on " year, 
and for others their " off ." year, and others again are more or less 
intermediate. It must be decided also whether amount of blossom or 
amount of fruit decides the " on " and " off " years ; it frequently 
happens that an increase in the amount of a tree's blossom is followed 
by a reduction in its fruit, and vice versa. Usually, however, the 
number of fruits must be taken as the best available indication. 
Then there is the question : How much should be allowed for the 
normal increase in crop due to the growth of the tree ? Again, there 
is the disturbance caused by the " rosy " apple aphis, a confusing 
factor which it is almost impossible to avoid altogether where any 
considerable number of trees is concerned ; a bad attack will frequently 
prevent a tree from forming more than a few scattered fruit buds. 
The best that can be done at present, therefore, is to state in general 
terms how the pruning has affected the development of the alternate 
bearing habit, with examples of individual tree records. 
Among the " unpruned " and " open centre " trees the habit has 
already become very obvious in every variety which had borne a 
heavy crop of fruit by 1920. The clearest of all is ' Early Victoria,' 
of which several unpruned trees, after cropping very heavily in their 
sixth year from planting (1919), had very little blossom in the following 
