Final answer:
The von Ebner glands are pure serous glands located in the area of circumvallate papillae; their ducts open into the moats around these papillae.
Step-by-step explanation:
The von Ebner glands are pure serous salivary glands located around the circumvallate papillae on the tongue. These glands secrete a watery fluid that contains enzymes essential for the initiation of digestion. Specifically, the von Ebner glands are located in the area of the circumvallate papillae, and their ducts open into the moats surrounding them. The function of these glands is to secrete serous fluid which aids in the beginning of the digestion of food, as well as helping to cleanse the taste buds situated in the circumvallate papillae, thus contributing to the sense of taste.