Yet another legume that is extraordinarily vigorous and prolific. Like the others, it develops nodules on its roots, under influence of a particular type of nitrifying bacillus, and so takes up nitrogen from the air, whereas other plants are obliged to depend upon soluble nitrogen compounds which are relatively rare. The value of such a crop as this in restoring nitrogen to the soil is inestimable.
This image is from: Luther Burbank: his methods and discoveries and their practical application. Volume 7 Chapter 3