Etymology - From the Greek arthro meaning jointed
This genus is quite suitable for cultivation as its members are relatively small, they grow fast, and produce impressive flowers. Even so, it is fairly uncommon in collections. Low shrubby stems branching from the bottom can reach 3 feet and are less than 2 1/2 inches in diameter. Anywhere from 9 to 19 low ribs feature closely grouped areoles with bristly golden spines - often with long central spines protruding sparsely through the numerous thin short radial spines. Flowers arise on long thin tubes that have fuzzy wool and hair-like spines; white, yellow, or pink on white. Fruits are green, scaly and round. All originate from Brazil.