Around this time last year, we had cowslips flowering in our garden. No such flowers this year, but I did spot this little ivy-leaved toadflax (Cymbalaria muralis) still in bloom. This plant is also known as Kenilworth Ivy and it is beautifully adapted to propagating itself in walls and stonework.
The flowers are phototrophic – this means that they grow towards the light which puts them in a good position for pollinating insects to arrive and fertilise them. Following fertilisation, the petals drop and it becomes photophobic, growing then away from the light. Using this simple rule, the seedhead will be propelled towards a darker place, such as back into a crevice in the wall where will find the right conditions to germinate and develop a new plant.
I can highly recommend this video on Getty Images which has used timelapse techniques to illustrate this behaviour perfectly.