CHAPTER IV 



FLORAL MECHANISMS 



IE have now come 

 to the interesting 

 group of flowers 

 which seem to 

 have invented for themselves 

 ingenious mechanisms to in- 

 sure their own cross-fer- 

 tilisation, and to prevent 

 self-fertilisation. Such a 

 mechanism has been re- 

 ferred to in the case of the 

 rose pogonia, as we saw on 

 page 8, with its pollen re- 

 tained in a lidded box that 

 opens only as the bee makes 

 its backward exit. Practi- 

 cally all the orchids have 

 mechanisms more or less 



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