Chap. I. INTRODUCTORY REMARKS. 9 



For the sake of detei mining certain points with respect 

 to inheritance, and without any thought of the effects 

 of close interbreeding, I raised close together two 

 large beds of self-fertilised and crossed seedlings from 

 the same plant of Linaria vulgaris. To my surprise, 

 the crossed plants when fully grown were plainly taller 

 and more vigorous than the self-fertilised ones. Bees 

 incessantly visit the flowers of this Linaria and carry 

 pollen from one to the other ; and if insects are ex- 

 cluded, the flowers produce extremely few seeds ; so 

 that the wild plants from which my seedlings were 

 raised must have been intercrossed during all previous 

 generations. It seemed therefore quite incredible that 

 the difference between the two beds of seedlings could 

 have been due to a single act of self-fertilisation ; and 

 I attributed the result to the self-fertilised seeds not 

 having been well ripened, improbable as it was that 

 all should have been in this state, or to some other 

 accidental and inexplicable cause. During the next 

 year, I raised for the same purpose as before two large 

 beds close together of self-fertilised and crossed seed- 

 lings from the carnation, Dianthus caryophyllus. This 

 plant, like the Linaria, is almost sterile if insects are 

 excluded ; and we may draw the same inference as 

 before, namely, that the parent-plants must have been 

 intercrossed during every or almost every previous 

 generation. Nevertheless, the self-fertilised seedlings 

 were plainly inferior in height and vigour to the 

 crossed. 



My attention was now thoroughly aroused, for I could 

 hardly doubt that the difference between the two beds 

 was due to the one set being the offspring of crossed, 

 and the other of self-fertilised flowers. Accordingly I 

 selected almost by hazard two other plants, which 

 happened to be in flower in the greenhouse, namely, 



