CHAP. I. INTRODUCTORY REMARKS. 23 



under the same net. If, however, the flowers which 

 had been presumably self-fertilised by me were in any 

 case afterwards crossed by Thrips with pollen brought 

 from a distinct plant, crossed seedlings would have 

 been included amongst the self-fertilised ; but it should 

 be especially observed that this occurrence would tend 

 to diminish and not to increase any superiority in 

 average height, fertility, &c., of the crossed over the 

 self-fertilised plants. 



As the flowers which were crossed were never cas- 

 trated, it is probable or even almost certain that I 

 sometimes failed to cross-fertilise them effectually, and 

 that they were afterwards spontaneously self-fertilised. 

 This would have been most likely to occur with dicho- 

 gamous species, for without much care it is not easy to 

 perceive whether their stigmas are ready to be fer- 

 tilised when the anthers open. But in all cases, 

 as the flowers were protected from wind, rain, and the 

 access of insects, any pollen placed by me on the 

 stigmatic surface whilst it was immature, would gener- 

 ally have remained there until the stigma was mature ; 

 and the flowers would then have been crossed as was 

 intended. Nevertheless, it is highly probable that 

 self-fertilised seedlings have sometimes by this means 

 got included amongst the crossed seedlings. The effect 

 would be, as in the former case, not to exaggerate 

 but to diminish any average superiority of the crossed 

 over the self-fertilised plants. 



Errors arising from the two causes just named, and 

 from others, such as some of the seeds not having 

 been thoroughly ripened, though care was taken to 

 avoid this error the sickness or unperceived injury of 

 any of the plants, will have been to a large extent 

 eliminated, in those cases in which many crossed and 

 self-fertilised plants were measured and an average 



