Microphotographs illustrating secretory cavities Secretory cavities are observed in parenchyma in some plant organs and are bordered by secretory cells that release their content into the cavity. Two exemles are shown on this page. Secretory cavity in a cross section through a celery petiole (see petiole anatomy ). Secretory cavities (ps) in a stem of tarragon : microphotograph of a part of a cross section in a stem (see stem anatomy )