Puccinia circaeae

The rust fungus Puccinia circaeae galls the leaves of Enchanter's-nightshade. The lower surfaces of leaves have raised areas bearing the telia, with a corresponding yellowing or reddish depression on the upperside.  There is no host alternation, and only telia are formed on the leaf undersides.    Some telia on the petioles and midribs are darker brown and germinate after over-wintering. 

The pale yellow uredinia of Pucciniastrum circaeae may also be present on Enchanter's Nightshade, but are not gall-causing.

host/gall

Photograph the rust on the host.  Ensure you have noted the host-plant species in your comments

Shaded places and woodlands, on Enchanter's-nightshade