SEX AND HEREDITY 



in position to the spots where he bears the pollen, some 

 may be deposited upon them. Thus unwittingly he will 

 have been the agent of transfer of the pollen from the 

 pollen-sac to the receptive stigma (Fig. 20). 



Such mechanisms have been elaborated in the course of 

 Descent in an infinite variety of detail. This is the 

 biological meaning of the attractive features of form, 

 colour, and scent which flowers have assumed. It may 



FIG. 20. 



Pollination of Salria. i = flower visited by Humble Bee, showing the projection 

 of the curved connective of the anther from the helmet-shaped upper lip of the 

 corolla, and the deposition of the pollen on the back of the Bee; 2=an older 

 flower, showing the elongated style with its stigma in such a position as to receive 

 pollen brought by a Bee from a younger flower ; 3-4, show the mechanism by 

 which the anther swings when pressed forward (as shown by arrow) by the proboscis 

 of the Bee. (After Strasburger.) 



even be seen how certain floral types have been adjusted 

 in relation to the visits of certain animals, and show 

 development parallel with them. A good instance is that 

 of the Aconite and the Humble Bee, in which the size 

 and shape of the flower is such as to accommodate the 

 animal. A study of their distribution across Europe and 

 Asia shows that the northern limit of both almost exactly 



j 



coincides. This suggests the importance of the Humble 

 Bee in the transfer of the pollen of the Aconite, while 

 the food which the flower offers may in some measure 



