  Graphene nanoribbons display an imperfectly understood transport gap. We
measure transport through nanoribbon devices of several lengths. In nanoribbons
of length greater than or equal to 250 nm we observe transport through multiple
quantum dots in series, while shorter constrictions of length less than or
equal to 60 nm display behavior characteristic of single and double quantum
dots. Dot size scales with constriction width. We propose a model where
transport occurs through quantum dots that are nucleated by background disorder
potentials in the presence of a confinement gap.
