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 
Fic. 56. Fic. 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 
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 
