Monday, October 6, 2014
This is the time of year when yew 'berries' begin to become conspicuous. Yew is one of only three British native species belonging to that division of the plant kingdom known as the gymnosperms - seed-producing plants that don't have flowers and don't enclose their seeds in an ovary to form a fruit. The other two are juniper (whose seed has a succulent outer coating - seed picture at the bottom of this post) and Scots pine (which carries its seeds in woody cones - see picture below).
In this picture you can seed the fully formed yew seed on the right, half covered by a pale green cup. This is the tissue that quickly expands to form the scarlet succulent aril, that you can see half-formed on the seed on the left. This squashy cup is attractive to birds that disperse the seeds, effectively judging from the numerous seedlings that appear in places where birds perch, such as crevices in old stone walls after the seed passes unharmed through the bird's gut. The seed itself is deadly poisonous to mammals but I've watched nuthatches wedge it in a bark crevice, hammer it open and eat it.
Here's a fully formed aril, which almost completely encloses the seed, like a scarlet doughnut.
Scots pine cone