The pineal gland is a pea-sized mass of tissue attached by a stalk to the posterior wall of the third ventricle of the brain It may play a part in initiating development of the gonads, but this is not known In mammals, it secretes the hormone melatonin The gland becomes calcified as age progresses, providing a useful landmark in X-rays of the skull
{s} resembling a pine cone; pertaining to the pineal gland, pertaining to the small endocrine gland in the brain which secretes the hormone melatonin (Anatomy)