82 THE STORY OF THE PLANTS. 



soon as a pollen-grain reaches the surface of the 

 stigma, it is held there by a sticky secretion, and 

 instantly begins to send out what is called ^pollen- 

 tube (Fig. 1 6). This pollen-tube makes its way 

 down the long stem or style which joins the stigma 

 to the ovary, and there comes in contact with the 

 undeveloped ovules. The ovules would not swell 

 and grow into seeds of themselves; but the mo- 

 ment the pollen-tube reaches them, they quicken 



FlG. 17. Flower of a shrubbery plant, Weigelia, with the petals 

 united into single corolla. I, entire flower ; II, the same, with 

 part of the corolla cut away ; III and IV, a stamen : k, calyx ; 

 d, corolla ; .r, stamen ; a, anther of the stamen ; g and , parts 

 of the pistil. 



into life, and begin to develop into fertile seeds. 

 Unfertilised ovules wither away or come to noth- 

 ing, but fertilisation by pollen makes them de- 

 velop at once into new plant colonies. 



Outside these essetitial organs, as botanists call 

 them, however, come, in handsome garden flowers, 

 two other sets of organs, more leaf-like in appear- 

 ance, but often brightly or conspicuously col- 



