The aspect ratio is the length divided by the width, maximum diameter (minimum circumscribed circle) divided by minimum diameter (maximum enclosed circle).

These are a few examples of pollens. There are many more in the Pollen section of this atlas.

These are a few examples of Textile Fibers. There are many more in the Textile Fiber section of this atlas.

. . . . . . Pinicoids

This habit shows parallel extinction with the alpha refractive index (1.490) parallel to the long axis an gamma (1.65) perpendicular to the long axis. Aspect ratio (Length/Width) is useful for separating the Pinus genus from diciduous plants also showing crystals with this habit. The relative thickness, shown by interference color, is another distinguishing feature.