136 



ZHSSOIVS WITS PLANTS 



by the wind, insects, or by man) is pollination. 

 There is a certain time when the stigma is recep- 

 tive, or ready to receive pollen, and this condi- 

 tion comes when 

 the pistil is full 

 grown : the stigma 

 then becomes vis- 

 cid, or sticky, or 

 much roughened, 

 as if to hold the 

 pollen. We now 

 see that the sta- 

 mens fall because 

 they have per- 

 formed their office ; 

 and the pistil per- 

 sists that it may 

 mature the seeds. Since no seeds could be pro- 

 duced without the joint action of pistil and sta- 

 mens, these members are known as the essential 

 organs of the flower. 



149. If the pupil were carefully to remove the 

 petals and sepals, and were then to apply the 

 pollen to the stigma, the pistil might mature and 

 good seeds form. It is evident, then, that the 

 floral envelopes do not hold the most vital rela- 

 tion to the office or purpose of the flower. They 

 are not necessarily essential to it. 



Fig. 13G. 

 Pistillate flowers of willow. 



