THE COMMON ARUM 



and which the}^ cannot find, and from their legs 

 and bodies are rubbed most, if not all, of the pollen 

 grains they brought with them from the arums 

 they previously visited. And here lies the essence 

 of the whole scheme. Each carpel in this manner 

 gets cross-fertilised with pollen from a neighbour- 

 ing plant. Of course, the arum will eventually 

 develop pollen of its own, but, as we have said, 

 cross-fertilisation results in stronger offspring than 

 those produced by self-fertilisation, and so the 

 plant lays itself out to effect that end. 



After a time when every ovary is fertilised, the 

 stigmas begin to shrivel and dry, and the hungry 

 insects, now almost on the point of starvation, at 

 last get their reward. Each carpel now secretes 

 a drop of nectar, and the thirsty midges greedily 

 drink it up as fast as it appears. This nectar, 

 however, is very strong, and after partaking of it, 

 the midges are gradually overcome and fall help- 

 less into the lower part of the floral chamber. 

 Yellow pollen then begins to shower down upon 

 them, for the male flowers are now arriving at 

 maturit3\ This pollen cannot, however, influence 

 the stigmas of the female flowers, for these have 

 now lost their sensitive nature. So there the 

 intoxicated insects lie in heaps as the pollen con- 

 tinues to fall upon them, indeed, they are literally 

 buried under it. 



There comes a time of respite, however, later, 

 when the flies begin to revive and feel that 

 they have had about enough of it and to realise 

 that a little fresh air would be an excellent tonic. 



41 



