Fig. 13

Morphometric analysis results: (a) Aspect Ratio of grains in tube (black) and intertube (white); (b) Circularity of grains in tube (black) and intertube (white). Each column represents the mean value of more than 50 grains in tube and intertube sectors respectively. Grains of the tubes are more elongated, with higher Aspect Ratio and lower Circularity, than grains that are casually deposited between adjacent tubes (intertubes)