What is Besseys Cactus

“Bessey’s Cactus,” it sounds a lot like a type of desert cactus named after a milking cow.  However, “Bessey’s Cactus” is, in fact, not a plant at all.  It is a scientific diagram that depicts how angiosperms, or flowering plants, evolved and are connected.  The shape of “Bessey’s Cactus” loosely resembles a beavertail cactus, and is named after the man who created it, Dr. Charles E. Bessey, a renowned botanist from the early 20th century.  

Dr. Charles E. Bessey was a botanist and educator from Ohio.  Bessey was recognized for his well-known diagram depicting the evolution of angiosperms – known as “Bessey’s Cactus.”  He was also well known for his innovative idea regarding education.  Bessey emphasized scientific and laboratory training in the agricultural curriculum.   He combined the university level agricultural program with the other university science departments so that they shared common core science courses.  Bessey was also committed to the idea of learning through practice rather than memorization.   In fact, his botany laboratory course was the first offered to undergraduates in the United States.  Despite his contributions to agricultural education, those were not his most notable works in the field of botany.  

His most memorable work in the field of botany was the development of the first explicitly phylogenetic classification of flowering plants – in other words the classification of flowering plants using the evolutionary relationship of the different species.  Bessey asserted that the angiosperms are the most diverse group of land plants, as well as the most primitive of the flowering plants. 

He contended that they are the most primitive because they possess several features considered close to gymnosperms – seed-bearing plants.  Gymnosperms are considered a more primitive type of plant due to the fact that seeds are not enclosed in an ovule.  Bessey argued that angiosperms derived from a single ancestral group. 

He developed a set of 28 rules for distinguishing genetic characteristics or evolutionary trends in plants.  Based on these characteristics and trends, he formed a classification system, and designed a diagram to represent how the plants were connected to each other and which of these plants were evolutionarily primitive or advanced.  This diagram was rather intricate, and was nicknamed “Bessey’s Cactus” because the branching, bending shape looks somewhat like a beavertail cactus.