Transverse serial sections through the seed cone of recent Pinus pinea, from the base of the cone to its apex, showing the presence of three spirals and their clockwise arrangement starting at ca. 17 s (out of a total of 35 s).
Video 1 from Gee, C. T. 2013. Applying microCT and 3D visualization to Jurassic silicified conifer seed cones: A virtual advantage over thin-sectioning. Applications in Plant Sciences 1(11): 1300039. doi:10.3732/apps.1300039