48 THE FERTILISATION OF FLOWERS, [CHAP. 



the other form (fig. 57) the mouth of the corolla-tube 

 is occupied by the anthers, and the stigma is half way 

 down the corolla-tube. These forms are termed "long- 

 styled " and " short-styled." Now it would seem 

 an easy matter for self-fertilisation to take place in 

 the " short-styled " flower, for the pollen could easily 

 fall on the stigma, and probably this does take place ; 

 but Mr. Darwin has shown us that such contact 

 seldom produces good seed. On the other hand self- 

 fertilisation is impossible in the " long-styled " form, 

 for the pollen on being shed falls to the bottom of 



FIG. 56. FIG. 57. 



the tube. There is another difference in these two 

 forms the short-styled form produces pollen grains 

 which are one-third larger than those of the long- 

 styled form, so that a pollen-grain from the long- 

 styled form would not contain sufficient material to 

 penetrate the whole length of its own style. Such 

 arrangements as this demonstrate most clearly the 

 pains Nature has taken to ensure cross-fertilisation. 

 It will be seen from the cuts that an insect visiting 



o 



the long-styled flower, in pushing its proboscis down 

 to the bottom of the tube, where the honey-glands 

 are, would dust it with pollen at a part which, when 



