CONTRIBUTIONS FROM THE WISLEY LABORATORY. 9 
To overcome this difficulty, and to obtain evidence that might be 
regarded as conclusive as to the ability of varieties to set and mature 
fruit with their own pollen, the work has since been carried out 
on pot-grown trees in an orchard-house erected for this purpose, a 
description of which, together with the method adopted for the pollina- 
tion of the flowers, was given in a recent report in this Journal on the 
Pollination of Plums.* 
As was expected, many of the varieties that gave negative results 
when self-pollinated outdoors were induced to set a few fruits when 
self-pollinated by hand under the more controllable conditions of 
the orchard house. Other varieties that set only a very few fruits 
when flowers were enclosed in bags outdoors set quite a fair crop when 
self -pollinated in the house ; but on no occasion did a variety that set 
fruit in bags outdoors fail to do so, and to a larger extent, when 
similarly pollinated in the house. 
Altogether about fifty varieties have been experimented with in 
the house, comprising all the commonly grown and 'market varieties, 
with almost all of which we have obtained conclusive evidence as to 
whether, and to what extent, they are self-fruitful or self-sterile. 
Two or more trees of each variety were dealt with over a period 
of several years, the cultural management being that usually followed 
for pot -grown trees in the cool orchard-house. 
Of the varieties tested under these conditions it was found that — 
(1) Only eight could be classed as self-fertile, and capable of setting 
a fair crop with their own pollen. 
(2) Thirty-nine were partly self -sterile, which means that they 
are able to set a few fruits with their own pollen, but certainly 
not enough to constitute what is generally known as a good 
crop. 
(3) Whilst three varieties only have failed to set any fruits at all 
when flowers were self -pollinated. 
Those varieties classed as self-fertile, and setting usually from 
15 to 20 per cent, of their blossoms when self -pollinated in the house, 
were ' Rev. W. Wilks ' (probably the most self-fertile variety we have), 
'Lord Derby,' 'Potts' Seedling,' ' Devonshire Quarrenden,' ' Ribston 
Pippin,' 1 Rival,' ' Duchess of Oldenburg,' and ' Early Victoria.' 
' Stirling Castle ' might almost be included in this group, but the 
amount of flowers that it appeared to be capable of setting with its 
own pollen varied greatly from year to year, and on the average of 
several years it is relegated to the class of partly self -fertile varieties. 
Although in the house we failed to obtain fruit-setting, when 
blossoms were self-pollinated, with three varieties — namely ' Cox's 
Orange Pippin,' ' Royal Jubilee,' and ' King's Acre Pippin ' — only two 
are really self -sterile so far as we can say at present, for the first-named 
of these set four fruits selfed outdoors in 1912, and I have since seen 
* Rawes, A. N., " Pollination in Orchards" (iv.) : " Self-Fertility and Self- 
Sterility of Plums," Journal R.H.S. xlvi. p. 353. 
