CONTRIBUTIONS FROM THE WISLEY LABORATORY. 615 



XXL— POLLINATION IN ORCHARDS. III. 



Self-fruitfulness and Self-sterility in Apples. 



By F. J. Chittenden, F.L.S. 



In a former paper * we have pointed out that some apples are self- 

 fertile and others self-sterile. The object of the present paper is to give 

 the results of some experiments upon the point carried out at Wisley 

 during the past few years. 



Method of Experiment. 



Preliminary experiments showed that most varieties of apples 

 pollinated themselves efficiently if left alone t ; for although the stigmas 

 are usually ripe before the pollen, the effective periods of the two 

 overlap a considerable time, and the stigmas come into contact with 

 the pollen of the same flower. Hand-pollination thus appeared to b 

 unnecessary (though it is possible that in a few varieties it may be 

 necessary, as it is in gooseberries when protected from insect visits). 

 For the purpose of these experiments, therefore, it was sufficient to 

 protect the flowers from wind-pollination and insect pollination by 

 covering them with insect-proof bags. Manilla paper bags were found 

 the best for the purpose ; and, out of many thousands used, very few 

 were found to have torn so as to admit chance insects : the results 

 where such tearing occurred were regarded as unreliable, and were 

 discarded. In one or two cases, chaffinches tore up the bags into 

 shreds, wherewith to fashion their nests, and, in a few, wasps used parts 

 of the bags for a similar purpose. The bags were placed in position so 

 that each enclosed a cluster of flowers a day or two before the oldest in 

 the cluster opened. Where the stigmas were slightly protruded beyond 

 the petals of one flower in the cluster before the bagging was done, 

 that flower was removed. The bags were securely tied at the mouth 

 round the spur, and often also to the branch bearing it, with rafBa. 

 They were left on until the petals had fallen (often until long after 

 they had fallen) and the stigmas had withered. About five thousand 

 clusters of flowers were bagged in this way during the three years 

 covered by the experiment as set out here. The number of flowers in 

 a cluster varies ; but if it be taken as six, it will be seen that nearly 

 thirty thousand apple flowers were experimented with in the period 

 under review. 



When the bags were removed, the number of immature fruits which 



* Chittenden, F. J., " Pollination in Orchards. I. Order of Flowering of 

 Apples," Journal R.H.S., xxxvii. p. 350. 

 ■j" Cf. Muller, Fertilisation of Flowers. 



