230 Flowers and their Pedigrees. 



their sensitive surface divided into numerous little 

 plumes or brushes, so as readily to catch any stray 

 pollen grain which may happen to pass their way. 

 Moreover, in each head, all the upper flowers have 

 pistils and embryo seed vessels only, without any 

 stamens ; while all the lower flowers have stamens and 

 pollen bags only, without any pistils. This sort of 

 division of labour, together with the same arrange- 

 ment of seed- bearing blossoms above and pollen- 

 bearing blossoms below, is very common among wind- 

 fertilised plants, and for a verj' good reason. If the 

 stamens and pistils were inclosed in a single flower 

 they would fertilise themselves, and so lose all the 

 benefit which plants derive from a cross, with its con- 

 sequent infusion of fresh blood. If, again, the stamens 

 were above and the pistils below, the pollen from the 

 stamens would fall upon and impregnate the pistils, 

 thus fertilising each blossom from others on the same 

 plant — a plan which is hardly better than that of self- 

 fertilisation. But when the stamens are below and 

 the pistils above, then each flower must necessarily be 

 fertilised by pollen from another plant, which ensures 

 in the highest degree the benefits to be derived from 

 a cross. 



Thus we see that the salad-burnet has adapted 

 itself perfectly to its new mode of life. Yet that 



