Seeds of Peach, Nectarines, and Almond
The picture shows the stone of the nectarine at the left, two peach stones in the center, and the almond stone at the right. Note the thin shell of the latter in comparison with the former. Doubtless the difference is due to selective breeding through countless generations.
This image is from: Luther Burbank: his methods and discoveries and their practical application. Volume 11 Chapter 3