THE 



EFFECTS 



OP 



CKOSS AND SELF-FERTILISATION. 



CHAPTER I. 



Introductory Eemarks. 



Various means which favour or determine the cross -fertilisation of 

 plants Benefits derived from cross-fertilisation Self-fertilisation 

 favourable to the propagation of the species Brief history of the 

 subject Object of the experiments, and the manner in which they 

 were tried Statistical value of the measurements The experi- 

 ments carried on during several successive generations Nature 

 of the relationship of the plants in the later generations Unifor- 

 mity of the conditions to which the plants were subjected Some 

 apparent and some real causes of error Amount of pollen em- 

 ployed Arrangement of the work Importance of the conclusions. 



There is weighty and abundant evidence that the 

 flowers of most kinds of plants are constructed so as 

 to be occasionally or habitually cross-fertilised by 

 pollen from another flower, produced either by the 

 same plant, or generally, as we shall hereafter see 

 reason to believe, by a distinct plant. Cross-fertilisa- 

 tion is sometimes ensured by the sexes being separated, 

 and in a large number of cases by the pollen and 

 stigma of the same flower being matured at different 

 times. Such plants are called dichogamous, and have 

 been divided into two sub-classes : proterandrous species, 



B 



