Chap. X. 



CROSS-FERTILISATION. 



381 



fectly pure plants, so that these flowers must have 

 been fertilised by pollen brought by insects from a 

 distance of between 500 and 600 yards.* It is of 

 course possible that some of these 202 flowers might 

 have been fertilised by pollen left accidentally in 

 them when they were castrated ; but to show how 

 improbable this is, I may add that Gartner, during the 

 next eighteen years, castrated no less than 8042 flowers 

 and hybridised them in a closed room ; and the seeds 

 from only seventy of these, that is considerably less 

 than 1 per cent., produced pure or unhybridised 



offspring.! 



From the various facts now given, it is evident that 

 most flowers are adapted in an admirable manner for 

 cross-fertilisation. Nevertheless, the greater number 

 likewise present structures which are manifestly 

 adapted, though not in so striking a manner, for self- 

 fertilisation. The chief of these is their hermaphrodite 

 condition ; that is, their including within the same 

 corolla both the male and female reproductive organs. 

 These often stand close together and are mature at 

 the same time ; so that pollen from the same flower 

 cannot fail to be deposited at the proper period on the 

 stigma. There are also various details of structure 

 adapted for self-fertilisation.t Such structures are 

 best shown in those curious cases discovered by H. 

 Miiller, in which a species exists under two forms, 

 one bearing conspicuous flowers fitted for cross-fertilisa- 

 tion, and the other smaller flowers fitted for self-fer- 



* Henschel's experiments 

 (quoted by Gartner, ' Kenntniss,' 

 &c, p. 574), which are worthless 

 in all other respects, likewise 

 show how largely flowers are in- 

 tercrossed by insects. He cas- 

 trated many flowers on thirty- 

 seven species, belonging to twenty- 



two genera, and put on their 

 stigmas either no pollen, or pollen 

 from distinct genera, yet they all 

 seeded, and all the seedlings raised 

 from them were of course pure. 



t ' Kenntniss,' &c. pp. 555, 576. 



j H. Miiller, ' Die Befruchtung, 

 &c. p. 443. 



