Whats growing on this leaf..

[Restless]

Found this leaf in the garden a few months back.. its the only leaf like it and the rest of the tree it came from looks fine.. strange

[RobSutton]

I think it a gall formed by either some sort of mite (perhaps an Eriophyes sp) or a Gall Midge. They are often very specific to certain plants so knowing what species of tree often helps you find out what species of mite or midge is causing the gall.

[charlieb]

Originally Posted by RobSutton

I think it a gall

Yup, what tree was it from?

[Chris Yeates]

mite gall Eriophyes tiliae - always (in my experience) on large-leaved lime Tilia platyphyllos

cheers

Chris