Chap. V. HETEEOSTTLED DIMOEPHIC PLANTS. 229 



from their seed 8 long-styled and 2 short-styled great- 

 great-great-grandchildren. In this last generation 

 short-styled plants appeared for the first time in the 

 course of the six generations, — the parent long-styled 

 plant which was fertilised with pollen from another 

 plant of the same form being counted as the first 

 generation. Their appearance may be attributed to 

 atavism. From two other long-styled plants, fertilised 

 with their own-form pollen, 72 plants were raised, 

 which consisted of 68 long-styled and 4 short-styled. 

 So that altogether 162 plants were raised from ille- 

 gitimately fertilised long-styled cowslips, and these 

 consisted of 156 long-styled and 6 short-styled plants. 



We will now turn to the fertility and powers of 

 growth possessed by the illegitimate plants. From 

 a short-styled plant, fertilised with its own-form 

 pollen, one short-styled and two long-styled plants, 

 and from a long-styled plant similarly fertilised three 

 long-styled plants were at first raised. The fertility 

 of these six illegitimate plants was carefully observed ; 

 but I must premise that I cannot give any satisfactory 

 standard of comparison as far as the number of the 

 seeds is concerned ; for though I counted the seeds 

 of many legitimate plants fertilised legitimately and 

 illegitimately, the number varied so greatly during 

 successive seasons that no one standard will serve well 

 for illegitimate unions made during different seasons. 

 Moreover the seeds in the same capsule frequently 

 differ so much in size that it is scarcely possible 

 to decide which ought to be counted as good seed. 

 There remains as the best standard of comparison the 

 proportional number of fertilised flowers which pro- 

 duce capsules containing any seed. 



First, for the one illegitimate short-styled plant. 

 In the course of three seasons 27 flowers were illegiti- 



