Veins occur in Orderly Ranks at Right Angles to the Axis & show a Repeating Pattern of Large & Small Veins.

Corn

Sugar Cane

Wheat (Triticum) Leaf

More Size Classes  are present.

Nerium Midrib giving rise to a Minor Vein. Minor Veins  often have Oblique Angles in Cross-Section.

Nerium Lamina - The darkly stained areas are Minor Veins

Nerium Leaf Margin - The Minor Veins are parallel to the screen & have stained darkly.