162 



riSUM SATIVUM. 



Chai\ V. 



namely, the early age at which the pollen-tubes are exserted ; 

 eight flowers not fully expanded were examined, and in seven ot 

 these the pollen-tubes were in this state; but they had not as 

 yet penetrated the stigma. Although so few insects visit tho 

 flowers of the pea in this country or in North Germany, and 

 although the anthers seem here to open abnormally soon, it does 

 not follow that the species in its native country would be thus 

 circumstanced. 



Owing to the varieties having been self-fertilised for many 

 generations, and to their having been subjected in each genera- 

 tion to nearly the same conditions (as will be explained in a 

 future chapter), I did not expect that a cross between two such 

 plants would benefit the offspring ; and so it proved on trial. In 

 1867 I covered up several plants of the Early Emperor pea, which 

 was not then a very new variety, so that it must already have 

 been propagated by self-fertilisation for at least a dozen genera- 

 tions. Some flowers were crossed with pollen from a distinct 

 plant growing in the same row, and others were allowed to 

 fertilise themselves under a net. The two lots of seeds thus 

 obtained were sown on opposite sides of two large pots, but only 

 four pairs came np at the same time. The pots were kept in the 

 greenhouse. The seedlings of both lots when between 6 and 7 

 inches in height were equal. When nearly full-grown they 

 were measured, as in the following table : 



Table LVII. 

 Pisum sativum. 



The average height of the four crossed plants is here 34*62, 

 and that of the four self-fertilised plants 39 68, or as 100 to 115. 

 So that the crossed plants, far from beating the self-fertilised, 

 were completely beaten by them. 



