Early Eocene
London Clay
Isle of Sheppy, Kent, England
9mm seed from the famous London Clay Flora.

Plant. Seed,

Here’s a seed that was washed out to sea before final burial.  The London Clay is famous for its marine fauna but a surprising amount of land plant fossils have been found in it too – several hundred species, in fact.

See:

“Fossil Plants of the London Clay” (The Palaeontological Society, 1983) by Margaret E. Collinson.