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a straight, longitudinal row of leaves on a stem or, sometimes, of lateral roots on the main root. In spiral leaf arrangement, the number of orthostiches is equal to the number of leaves in a leaf cycle (the spiral line between two leaves in one orthostichy). In whorled leaf arrangement, there are twice as many orthostiches on a shoot as leaves in a whorl. Four orthostiches characterize decussate leaf arrangement.