CHAP. II. 



SUMMARY OF OBSERVATIONS. 



53 



The mean height of the self-fertilised plants in 

 each of the ten generations is also shown in the 

 accompanying diagram, that of the intercrossed plants 

 being taken at 100 ; and on the right side we see 

 the relative heights of the seventy-three intercrossed 

 plants, and of the seventy-three self-fertilised plants. 

 The difference in height between the crossed and 



Diagram showing the mean heights of the crossed and self-fertilised 

 plants of Iponvxa purpurea in the ten generations ; the mean height of the 

 crossed plants being taken as 100. On the right hand, the mean heights of 

 the crossed and self-fertilised plants of all the generations taken together 

 are shown. 



self-fertilised plants will perhaps be best appreciated 

 by an illustration : If all the men in a country were 

 on an average 6 feet high, and there were some families 

 which had been long and closely interbred, these 

 would be almost dwarfs, their average height during 

 ten generations being only 4 feet 8 inches. 



