Variation in Walnut Leaves
As in his work with all other plants, Mr. Burbank pays strict attention to the selection of those seedlings which have the most and best leaves, and the best leaf formation. Many seedlings, promising in other respects, have faulty leaves, and promptly go to swell the bonfire of rejected plants which Mr. burbank burns every few months.
This image is from: Luther Burbank: his methods and discoveries and their practical application. Volume 2 Chapter 5