The "Robusta" Cactus
Not an inch of wasted space here. It would be difflcult to mass the slabs more closely together had they been adjusted by hand. In many places they overlap one another like shingles on the roof of a house. Yet the individual slabs are of good size and healthy in appearance, and the plants thrive notwithstanding their scant breathing space.
This image is from: Luther Burbank: his methods and discoveries and their practical application. Volume 8 Chapter 7