The oaks at Skelton Lake have long-stalked acorns so, as the stalk botanically is the peduncle, these are common oaks, also known as pedunculate oak.
The old oak apple is a gall caused by the gall wasp Biorhiza pallida. The larvae develop inside the corky gall, so the holes are probably where the winged adult gall wasps have emerged during the summer but they might also be where parasitic gall wasps that feed on the Biorhiza larvae have emerged. There are also inquilines, insects that use the gall for the development of their larvae without preying on the original occupants.
When the Biorhiza wasps emerge in the summer, the females lay their eggs on the roots of the oak and an all-female generation of wingless gall wasps will emerge in winter about 18 months later. These females emerge climb up to lay their eggs in the leaf buds of the oak and it’s the leaf buds which develop into oak apples.
Rough-stalked feather-moss, Brachythecium rutabulum, is a common moss on wood and rocks. It also grows in grassland and can be considered a weed in lawns. I’ve been raking and scarifying our back lawn in preparation for the winter and this looks like the moss that I was raking up. I filled a large trug with moss and dead grass.