Encyclopedia article on mechanical cotton harvesters, explaining why cotton's uneven ripening makes machine picking difficult and why earlier machines using claws, card clothing, suction or electrified belts failed. It describes Charles T. Mason Jr.'s selective 'stem', a slotted sheet-metal cylinder with guarded teeth that catches only elastic lint, and the Mason harvester that carries rotating stems on vertical shafts through the cotton row. It gives test results from the National Cotton Planters' Association and a list of Mason's patents from 1883 to 1886.