In message , Jaques
d'Alltrades writes

The seeds are more like big elm seeds than ash at first sight, with the
seed in the middle of the long membrane of thin translucent green
material. They grow in clusters like ash keys.

http://www.users.zetnet.co.uk/hi-fi/mystree.jpg

Possibly Pterocarya or Carya. The leaf looks more like Carya than
Pterocarya, but I haven't seen the seed of Carya.
--
Stewart Robert Hinsley