HETEROSTYLISM. 



211 



this plant, he found that the flowers variously crossed gave 

 the following results (omitting decimals under .6) : — * 



From these results Mr. Darwin concluded that each form 

 of pistil is as fully fertile as possible, only when it receives 

 pollen from the stamens of the same length as itself, these 

 being legitimate unions. It will be seen that the mid-styled 

 form is the most fertile of the three when legitimately fer- 

 tilised ; and as all illegitimate unions of the long- and short- 

 styled forms were too sterile for any averages, the mid-styled 

 form is also the most fertile when illegitimately crossed, and 

 is least fertile with its own stamens, as indicated above by 

 the (t). Hence self-fertilisation in this species is at a very 

 low ebb. 



A few more remarks deduced from Mr. Darwin's observa- 

 tions t niay be added here. From the three forms occurring 

 in approximately equal numbers in a state of nature, and from 

 the results of sowing seed naturally produced, there is reason 

 to belief that each form, when legitimately fertilised, repro- 

 duces all three forms in about equal numbers. 



When they are illegitimately crossed with pollen from 

 the same form, they evince a strong but not exclusive tendency 

 to reproduce the parent form alone. 



* Forms of Flowers, p. 152. f L.c. p. 203. 



