The leaf venation as formed in a tensorial field Y. Couder, L. Pauchard, C. Allain, M. Adda-Bedia and S. Douady Eur. Phys. J. B, 28 2 (2002) 135-138 Published online: 19 July 2002 DOI: 10.1140/epjb/e2002-00211-1