There is a paper in the American Journal of Botany for September 2012 by Durkovic et al. on the significance of leaf traits in the evolution of Sorbi.
It is deeply scientific as this excerpt from the abstract will show "A recently developed atomic force microscopy technique, PeakForce quantitative nanomechanical mapping, was used to characterize the topography of cell wall surfaces of tracheary elements and to map the reduced Young’s modulus of elasticity."
Further details at: http://www.amjbot.org/content/early/2012/08/23/ajb.1100593.abstract
