40 Pollination in Orchards 



what can be its explanation ? A hypothesis which would fit all the facts 

 has, so far, evaded us, nor have we been able to form a mental picture 

 of what self-sterility means, and the whole question seems wrapped up 

 with another of the deepest biological significance, viz. what is the real 

 meaning of individuality ? 



There is some evidence that this self-steriUty is not absolute in, at 

 least, some varieties. That is, a variety self-sterile here, may be self- 

 fruitful somewhere in the range of its distribution, or in some seasons. 

 It seems almost that, where the variety " does " best, it is more likely 

 to be self-fruitful (whether self-sterile or not, the recorded observations 

 do not make clear, though our own experiments tend to show that, e.g. 

 in " Cox's Orange Pippin," in which self-steriUty is the rule, when excep- 

 tions occur, seed is produced). This fact no doubt explains the con- 

 tradictory evidence afforded by different observers on such a pear as 

 " William's Bon Chretien," which produces fruit without foreign pollen 

 in some places, not in others. 



There is the further question as to whether vegetative vigour may 

 not be a factor in the production of the seedless fruits already alluded 

 to. It may be so, for we find vigorous trees of the pears " Conference " 

 and " Durondeau " almost invariably very fruitful, and, where protected 

 from foreign pollen, bearing seedless fruits, while, among apples, " Stirl- 

 ing Castle " very rarely fails. 



It seems quite possible that the pollen of a self-fruitful variety such 

 as these may have the function of stimulating the development of what 

 may be called the vegetative part of the fruit, though it fails to eft'ect 

 fertilization. This is a very commonly observed phenomenon in the 

 case of many orchids, even foreign bodies falHng upon the stigma 

 causing the production of fruits (of course, usually seedless). An 

 interesting instance of the effect of stimulation of a rather novel character 

 came to my notice not long since, and it was not an isolated instance. 

 All the pears on a tree, except those attacked by the pear midge Diplosis 

 pyrivora, fell very early, failing to swell, apparently owing to defective 

 fertihzation. Those attacked remained till the end of May, and, as is 

 their wont, swelled very considerably. I commend this observation 

 to the notice of our entomological members. The case of the absolute 

 effect of the stimulus of egg-laying, or of the larval presence, is not quite 

 conclusive, but it is certainly suggestive. 



Some Economic Aspects of the Question. It is clear that a knowledge 

 of varieties dependably self-fruitful would at once show what varieties 

 might be planted in large blocks without fear of failure from this cause. 



