1. (root cap) A hood-shaped cap of parenchymatous cells at the tip of the root that protects the root meri-stem from abrasion as it grows through the soil. It is derived from a separate meristem, the calyptrogen, and may be augmented by periclinal divisions of the cells at the surface of the root.
2. A layer of cells that protects the developing sporophyte in the mosses and liverworts. It forms a hood over the capsule and is developed from the venter wall of the archegonium. At maturity it ruptures by elongation of the seta.