Chart of the possible shapes and forms of leaves. For instance, you could have a leaf of lanceolate shape with a crenate margin and reticulate veins.

**Update:** kottke.org reader Flip passes along this article about the wavy edges of flowers, leaves and even garbage bags, summarizing it thusly:

Basically, as the leaf grows it is constrained to a 2-d surface, but the cells of some leaves reproduce fast enough to require more surface area than a pi-r-squared plane surface can provide. Its only recourse is to buckle out-of-plane, giving the wrinkles. Since the exuberant growth continues as the leaf grows outward, the buckling process repeats and you get the multi-scale (ripples on ripples on ripples) shape that you see in kale and daffodils.

(thx, flip)