Armored Against Its Enemies
The desert cactus shown in the accompanying direct color photograph print portrays a typical arrangement of armor, although many forms of cactus are more heavily spined even than this. In addition to the large bristling spines which fan out in every direction, there are hidden behind each rosette a bundle of undeveloped spines, numbering often as high as ten thousand to each eye. When the outward spines are cut off, these push their way forward with surprising rapidity to protect the gap in the armor.
This image is from: Luther Burbank: his methods and discoveries and their practical application. Volume 1 Chapter 1