o& CROSS-FERTILISATION. Chap. X. 



It may be admitted as almost certain that some 

 structures, such as a narrow elongated nectary, or a 

 long tubular corolla, have been developed in order 

 that certain kinds of insects alone should obtain the 

 nectar. These insects would thus find a store of nectar 

 preserved from the attacks of other insects ; and 

 they would thus be led to visit frequently such 

 flowers and to carry pollen from one to the other.* 

 It might perhaps have been expected that plants 

 having their flowers thus peculiarly constructed would 

 profit in a greater degree by being crossed, than 

 ordinary or simple flowers; but this does not seem 

 to hold good. Thus Tropteolum minus has a long 

 nectary and an irregular corolla, whilst Limnanthes 

 douglasii has a regular flower and no proper nectary, 

 yet the crossed seedlings of both species are to the 

 self-fertilised in height as 100 to 79. Salvia coccinea 

 has an irregular corolla, with a curious apparatus by 

 which insects depress the stamens, while the flowers 

 of Ipomcea are regular; and the crossed seedlings of 

 the former are in height to the self-fertilised as 

 100 to 76, whilst those of the Ipomcea are as 100 to 

 77. Fagopyrum is heterostyled and Anagallis collina 

 is homostyled, and the crossed seedlings of both are 

 in height to the self-fertilised as 100 to 69. 



With all European plants, excepting the compara- 

 tively rare anemophilous kinds, the possibility of 

 distinct individuals intercrossing depends on the 

 visits of insects; and H. Miiller has proved by his 

 valuable observations, that large conspicuous flowers 

 are visited much more frequently and by many more 

 kinds of insects, than are small inconspicuous flowers. 

 He further remarks that the flowers which are rarely 



* See the interesting discussion on this subject by H Miiller, 

 Pie Befruchtvmg,' Ac. p. 431. 



