Denton's Challenge: Are Leaf Shapes Adaptive?

In his new book Evolution: Still a Theory in Crisis, Michael Denton provides a cavalcade of examples of non-adaptive forms in nature. On page 77, he points to angiosperm leaves as a case visible to everyone.

It is not only the unicellular world that abounds with what appear to be abstract formal patterns. Even on the most cursory and passing observation of some of the most familiar natural forms, such as the forms of leaves and the variety of phyllotactic arrangements that might be observed...