Click the number at the start of a key lead to highlight both that lead and its corresponding lead. Click again to show only the two highlighted leads. Click a third time to return to the full key with the selected leads still highlighted.
1 Mature involucre 1.5-3 cm long, the lobes flattened and laciniate; young twigs and petioles stipitate-glandular; [section Corylus, subsection Corylus]
1 Mature involucre 4-7 cm long, extended into a tubular beak; young twigs and petioles villous, glandless; [section Corylus, subsection Siphonochlamys]