II 



THE POLLINATION AND FERTILISATION OF FLOWERS 



Since flowers are the reproductive organs of the plant it seems only 

 natural to suppose that the wonderful variety of colour and form 

 which they exhibit might have some connexion with the processes 

 concerned in the propagation of their respective species, and the 

 more we study the nature of the flowers and observe the methods by 

 which pollen is transferred from stamens to stigmas, the stronger 

 becomes our conviction that the diversities mentioned are all more 

 or less connected with the one great function of reproduction. 



This being the case, we propose to devote a short chapter to a 

 simple account of the uses of the parts of a flower, and to the various 

 contrivances on the part of the plant to secure the surest and best 

 means of perpetuating the species. 



It has already been stated that the stamens produce pollen cells, 

 and that the ovary contains one or more ovules. 

 As soon as the anthers are mature, they open and 

 set free the pollen cells they contained. A stigma 

 is said to be mature when it exposes a sticky surface 

 to which pollen cells may adhere, and on which these 

 cells will grow. When a pollen cell has been trans- 

 ferred to such a stigma, it is nourished by the fluid 

 secreted by the latter, and sends out a slender, 

 hollow filament (the pollen tube) which immediately 

 begins to descend through the stigma, and through 

 the style, if any, till it reaches the ovary. tollek cells 



'''*'' -^ THROWING OUT 



Should the reader desire to watch the growth of their tubes. 

 the pollen tubes, he can easily do so by shaking 

 some pollen cells (preferably large ones, such as those of some 

 liHes) on to a solution of sugar, and watching them at intervals 

 with the aid of a lens. In the course of a few hours the pollen 



