A Mosaic Leaf
When a purple-leaved plum is hybridized with a green-leaved plum, the hybrids of the first generation have green leaves, but purple leaves reappear among the varying hybrids of the second generation. Occasionally, however, a cross between purple-leaved and green-leaved varieties, where the varieties lie near the limits of affinity, results in a condition that might be described as a mosaic, the leaves partaking of the characteristics of both ancestral strains. This picture illustrates such a case.
This image is from: Luther Burbank: his methods and discoveries and their practical application. Volume 3 Chapter 1