The most thorough examination of prickly pears as a food source is the classic study done in the first decade of this century
by David Griffiths and R. F. Hare,The Tuna as Food for Man, USDA, Bureau of Plant Industry, Bulletin No. 116 (1907). Griffiths followed this general treatment with,The Prickly Pear as a Farm Crop, USDA, Bureau of Plant Industry, Bulletin No. 124 (1908), reporting early experimental efforts at cultivation in southern
Texas.