CONTRIBUTIONS FROM THE WISLEY LABORATORY. II 
self -fertile variety, numbers of flowers were self-pollinated, and on 
the other side many others cross-pollinated with pollen from a wide 
range of varieties, the selfed portion set 17 per cent, of the blossoms 
pollinated, whilst the crossed portion set 40 per cent. 
Of course such large numbers of flowers setting fruit are not to 
be expected outdoors under ordinary orchard conditions, but in a 
somewhat like proportion cross-pollination may be expected to 
increase fruit-setting. 
So that, not only is cross-pollination essential for good fruit-setting 
with the great majority of varieties, but it is beneficial and likely 
to induce larger settings of fruit with all. 
With a view to determining the value of different varieties for 
providing pollen for the cross-pollination of others, a very great number 
of comparative tests have been made. 
Although even yet we have been unable to carry out every combina- 
tion possible between the numerous varieties we have under 
observation, a great deal of evidence has been obtained, from which 
valuable conclusions may be drawn. 
So far we have not discovered any instances of inter-sterility existing 
among varieties of apples, as was found in plums and cherries, and 
from the wide range of varieties tested it seems unlikely that we shall. 
The results of our experiments suggest that there is little or no 
ground for the supposition that such and such a variety is the only 
one to plant for the successful cross-pollination of any other, but 
rather point to the fact that pollen from any one variety is capable 
of inducing just as good a setting of fruit on a given variety as is any 
other. 
So much depends upon the health of the tree, the amount of pollen 
the blossoms produce in a particular year, and the viability of the 
pollen — all of which appear to vary considerably in each variety — that 
extensive work on this point under orchard conditions is difficult; 
but from the trees which we have under observation in the orchard-house 
we have found no evidence to show that " pollen preference" exists 
among varieties. 
Since no cross-incompatibility and no pollen preference apparently 
exist among varieties of apples, the choice of varieties to plant for 
efficient cross-pollination depends almost entirely upon the flowering 
period, for it will be obvious that the closer the coincidence of the 
flowering periods of the varieties to be planted together, the more 
efficient is the cross-pollination likely to be between them. 
In a previous paper on " Pollination in Orchards "* a list was given 
of some 170 varieties, with the relative time of flowering of each. This 
list was made from records obtained over a period of four years, but 
we have now records of the flowering periods of all these varieties 
for thirteen years. Comparisor.s recently made show that the order 
of flowering, although varying slightly in one or two instances, is 
* Chittenden, F. J., " Pollination in Orchards " (i.), Journal R.H.S., vol. 
xxxvii. p. 350. 
