Apium graveolens var. dulce
In temperate countries, celery is also grown for its seeds. Actually very small fruit, these "seeds" yield a valuable volatile oil used in the perfume and pharmaceutical industries. They also contain an organic compound called apiol. Celery seeds can be used as flavouring or spice, either as whole seeds or ground and mixed with salt.
The use of celery seed in pills for relieving pain was described by Aulus Cornelius Celsus around AD 30. Celery seeds contain a compound, 3-n-butylphthalide, that has been demonstrated to lower blood pressure in rats.