What is "nervation"

Nervation \Ner*va"tion\ (n[~e]r*v[=a]"sh[u^]n), n. The arrangement of nerves and veins, especially those of leaves; neuration.

The outlines of the fronds of ferns, and their nervation, are frail characters if employed alone for the determination of existing genera.
--J. D. Hooker.

n. A pattern of nerves, e.g. as seen on a leaf.