SEM images of upper, middle and basal part of Gymnocalycium kieslingii subsp. castaneum. a surface of spine from basal part covered with mineral deposition b, c surface of spine from basal part with a few epidermal cells d damaged, bent and deformed tip of spine from basal part e surface of spine from middle part with clearly visible epidermal cells sharply bent upward in upper part f surface of spine from upper part with very clearly visible and undamaged epidermal cells g undamaged top part of spine from upper part h epidermal cells of spine from upper part, bent lengthwise in its central part. Scale bar = 200 µm.