268 SUMMAEY OF MEASUREMENTS. CflAr. VII. 



fertilised plants of the fourth illegitimate generation, 

 were raised. The former were to the latter in 

 height as 100 to 46, and in fertility during one 

 year as 100 to 5, and as 100 to 3 5 during the next 

 year. In this case, however, we have no means of 

 distinguishing between the evil effects of illegitimate 

 fertilisation continued during four generations (that is, 

 by pollen of the same form, but taken from a distinct 

 plant) and strict self-fertilisation. But these two 

 processes perhaps do not differ so essentially as at 

 first appears to be the case. In the following experi- 

 ment any doubt arising from illegitimate fertilisation 

 was completely eliminated. 



(13.) Primula verts. (Equal-styled, red-flowered 

 variety). Flowers on plants of the second self-fertilised 

 generation were crossed with pollen from a distinct 

 variety or fresh stock, and others were again self- 

 fertilised. Crossed plants and plants of the third self- 

 fertilised generation, all of legitimate origin, were 

 thus raised ; and the former was to the latter in height 

 as 100 to 85, and in fertility (as judged by the number 

 of capsules produced, together with the average number 

 of seeds) as 100 to 11. 



Summary of the Measurements in Table C. This 

 table includes the heights and often the weights of 

 292 plants derived from a cross with a fresh stock, 

 and of 305 plants, either of self-fertilised origin, or 

 derived from an intercross between plants of the same 

 stock. These 597 plants belong to thirteen species 

 and twelve genera. The various precautions which 

 were taken to ensure a fair comparison have already 

 been stated. If we now look down the right-hand 

 column, in which the mean height, weight, and 

 fertility of the plants derived from a cross with 

 a fresh stock are represented by 100, we shall see 



