242 



THE LIFE OF THE PLANT 



visit flowers ; the bright colouring, the size and the 

 perfume of flowers serve as means for attracting them. 

 It has been proved that bees possess the faculty for 

 distinguishing between colours. By smearing with honey 

 differently coloured surfaces, we can train insects to associ- 

 ate the impression of a certain colour with the presence 

 of honey. Cross-fertilisation takes place as a result of a 

 division of sexes in the flowers themselves ; the staminate 

 and pistillate flowers may be distributed either on one 

 and the same plant or on diff^erent plants : while in 

 hermaphrodite flowers cross-fertilisation is achieved by 

 the ripening of stamens and pistils at different times, 

 whereby self-fertilisation becomes impossible. But most 

 convincing of all are the numerous facts which show all 

 the parts of the flower to be adapted in structure and 

 disposition to the form and habits of the visiting insect, 

 so that in flying from one flower to another the insect is 



bound to touch the 

 stamen of one flower, 

 and then with the 

 same part of its body 

 the stigma of an- 

 other. Let us limit 

 ourselves to a few 

 illustrations. 



There are many 

 flowers the parts of 

 which, instead of 

 being arranged in the 

 usual regular way 

 round the centre, are 

 distributed in such a 

 way that right and 

 left sides, top and 

 bottom can be dis- 

 Labiate flowers may serve as an example 

 Such a form is obviously very convenient 



Fig. 69. 



tinguished. 

 (fig. 69, 2) 



