What is (a) Depressed in the middle, like a navel, as a flower, fruit, or leaf; navel-shaped; having an umbilicus; as, an umbilicated smallpox vesicle. (b) (Bot.) Supported by a stalk at the central point called?

umbilicate — (a) Depressed in the middle, like a navel, as a flower, fruit, or leaf; navel-shaped; having an umbilicus; as, an umbilicated smallpox vesicle. (b) (Bot.) Supported by a stalk at the central point. (Webster's 1913.)