I went up to the bog expecting to find some Bog Cotton. Instead I found this Harestail Cotton-grass.
It turns out that there are two different versions of the Primrose flower. Pin-eyed - in which the stigma protrudes further than the anthers - on the left, and Thrum-eyed - in which the anthers protrude further than the stigma - on the right.
A long-tongued insect can reach the nectar at the base of the tube and when it visits a pin-eyed flower, pollen is rubbed on the middle part of its proboscis from the anthers midway down the tube. As it goes from flower to flower on the same plant, there is only the same result, but when it visits a different plant with thrum-eyed flowers, then the pollen on the proboscis is in exactly the right place to rub on the stigma which only reaches half-way up the tube. The head, meanwhile, is getting pollen from the long stamens at the throat of the tube, which in turn is transferred to the tall stigmas of the next pin-eyed flower visited. Thus self-pollination is less likely and each version of the flower is cross-fertilized.
I visited Drumboe woods again, today, and saw the Great Woodrush in large numbers - carpeting the woods in many places.
When I see the bud bursting on the Horse Chestnut, I'm always in awe of the great amount of growth going on in such a tiny space.