TRANSACTIONS OF SUB-SECTION K. 



590 



4. Self -sterility and Self-fertility in Plums. By W. 0. Backhouse. 



The object of these experiments when first undertaken was not to see which 

 varieties of plum were self-sterile and which self-fertile, but to start a systematic 

 inquiry into the gametic composition of our commoner plums, with a view to 

 putting the raising of new plums on a scientific basis. 



Accordingly, in 1910 suitable branchlets of the following plums were en- 

 closed in paper bags, before the flowers had opened, to exclude insects and 

 foreign pollen. Subsequently, when at the height of the flowering period, the 

 bags were taken off and the flowers carefully hand pollinated ; being then 

 covered up again immediately. 



Victoria . 



River's Early Prolific 

 Greengage 



Results. 



7 bags, covering on an average twenty flowers 

 each. Nearly every flower set, and the fruit 

 had to be heavily thinned. 



8 bags ; set, nine fruits. 



5 bags ; set, four fruits, all in one bag, which 

 was broken. 



Nine emasculated flowers of greengages, crossed River's Early Prolific, gave 

 This year, this was repeated and extended, giving results as 



nine seeds, 

 follows : — 



Trees in Open. 

 28 bags, 2 fruits. 



River's Early Prolific 



Victoria .... 30 bags ^ 



Prince Englebert . . 3 „ 



Czar . . . . 12 „ 



Pershore . . . . 18 ,, 



Yellow Magnum Bonum 15 ,, 



Damson (var.) . . 7 ,, 



A ' sloe ' Prunus spinosa 11 bags 



Histon Gage . . . 10 ,, 



Early Orleans . .28 ,, 



Late Orleans . . 15 ,, 



Late Orange . . .19 ,, 



Sultan . . . 16 ,, 



Korke's Blue 3 ,, 



All set to such an extent that 

 -the fruit had to be heavily thinned 

 to allow it to develop properly. 



-All set absolutely nothing. 



Pot trees flowered in a fruit-house of the John Innes Horticultural Insti- 

 tution under conditions where insects were almost entirely excluded, and which 

 were carefully hand pollinated with their own pollen, flower by flower. 



Denniston's Superb 

 Early Transparent 

 Reine Claude Violette . 



River's Early Prolific . 



2 Trees Coe's Golden Drop 



Washington 



Late Transparent. 



Blue Imperatrice 



Early Greengage 



Old Greengage 

 2 Trees Reine Claude d'Althan. 



\ 



•Set nearly every flower. 



10 fruits out of 110 flowers circa. 



Set nothing, with the exception of one 

 Reine Claude d'Althan fruit and two on 

 Old Greengage, which were all in posi- 

 tions which make an accidental touch 

 very probable. 



It is interesting to note that in the above cases where a plum is self-sterile 

 if the flower is not pollinated at all, it falls in three or four days. If self-pol- 

 linated, the carpel may swell to the size of a culinary pea before dropping 

 and on sectioning there is seen to be a great development of nucellus tissue. 



