有些生物分子呈螺旋状.Some biological molecules have the form of a helix.叶片呈螺旋状开略带紫色白花的北美紫菀.North American perennial with apparently whorled leaves and showy white purple - tinged flowers.欧洲兰花,花色雪白,总状花序较短、呈螺旋状.European orchid havin...