Ever wonder how male and female parts dont fertilize themselves when they are on the same plant? To reduce sexual interference on hermaphroditic angiosperms (both sex flowering plants) a process called Herkogamy is in place. This is a strategy to reduce interactions between the anthers (male) and stigmas (female) of the same plant by supplying spatial separation of these males and female parts.
Two forms of this are the most common Pin and Thrum:
Pin or Approach Herkogamy is the presentation of the stigma above the anthers. This arrangement of sex organs causes floral visitors to first contact the stigma, before removing pollen from the anthers.
Thrum or Reverse Herkogamy is displayed when the stigma is located below the anthers. This arrangement causes floral visitors to first contact the anthers before the stigma.