The undifferentiated sheath which encloses root cap in a monocot seed is termed as:

✅Explanation:
-A typical monocot seed has a short axis bearing plumule & a radical. The plumule differentiates to form the shoot while the radical forms the root system.
-The plumule is surrounded by a protective conical-shaped layer called the Coleoptile.
-The radical and root cap is surrounded by the protective undifferentiated sheath called the Coleorhiza.
-Both these sheaths provide protection to the developing root & shoot tips.
-Thus, the undifferentiated sheath which encloses the root cap in a monocot seed is termed as Coleorhizae.

🔴Additional Information:
-Calyptogen: It is a region of the root apical meristem that divides to form cap like protective structure, the root cap.
-Calyptra: It is a hood or cap-like structure present on the capsule of the sporophyte of certain mosses. It is formed by the expanded wall & neck of archegonium.