A Cluster of Cactus Pears
This shows the typical and characteristic distribution of the fruit about the borders of the cactus slabs. It is not unusual, however, for a fruit to appear also on the sides of the slab, starting from amidst the clusters of spinules; or, in case of Mr. Burbank's spineless varieties, from the indentations that mark the former location of the spinules.
This image is from: Luther Burbank: his methods and discoveries and their practical application. Volume 6 Chapter 7