How do cactuses pollenate if they don’t have flowers growing on them?

Question: How do cactuses pollenate if they don't have flowers growing on them?

Asked by loki514 to MarkF, Michael, Panos, Sarah on 24 Jun 2010 in Categories: General.
- Sarah Burl answered on 24 Jun 2010:
  
  Catuses do have flowers on them, some flower rarely but enough to pollenate them when needed.
- Panos Soultanas answered on 24 Jun 2010:
  
  It is not true that all cactuses do not have flowers. Some cactuses do have flowers. The appearance of such flowers varies greatly between different cacti. Some flower for a week, others only for few hours during the night, while others only flower when the conditions are exceptional (i.e. lots of water and sun).
  
  The cacti that do not have flowers pollenate themselves. They are known as autogamous. the word comes from the Greek words autos (self) gamous (marriage) i.e. they are married to themselves..! They form seeds themselves and pollinate them themselves and so there is no need to have flowers to attract insects for cross-pollenation.
- Michael Loughlin answered on 24 Jun 2010:
  
  they do have flowers
  http://www.fotosearch.com/digistock/cactus-flowers/DGK122/
  
  so they pollinate by wind, insect and some are self pollinators
  
  we just don’t tend to see the flowers that often..but they are there…good question though…i had to go check

Question: How do cactuses pollenate if they don't have flowers growing on them?