Seedling Pear Trees
The wild pears have a protective equipment of thorns, as illustrated by the seedlings at the right. These thorns are no longer needed to protect the cultivated pear, and they have been entirely discarded by the best cultivated varieties, as illustrated by the seedling at the left. An occasional seedling, however, still reverts to the thorny type, showing the strong hold of heredity.
This image is from: Luther Burbank: his methods and discoveries and their practical application. Volume 4 Chapter 4