The "veins" in leaves are primary vascular bundles. They transport water and photosynthates via primary xylem and primary phloem. The primary vein is located in the center of the leaf and is termed the midrib. From this vein branch the secondary veins, and from these veins branch the tertiary veins.

The venation in Vitis species forms a netted, or reticulate, pattern.

Leaf Abaxial Surface
Leaf veins intersect to form enclosed areas called areoles.
Leaf Abaxial Surface
In the image at left, the blue arrow indicates a leaf vein which terminates inside an areole.
Leaf Clearing