. Self-organizing formation of vascular system of plant leaves: Co-orientation between auxin flux and pump proteins.) thcor Biol 236: 366- 375. 67. Gerhart J, C Lowe, M Kirschner (2005). Hcmichordatcs and the origin of chordates. Curr Opin Genet Dev 15: 461-467. Gilligan DM, DA Briscoe, R Frankham (2005).