Protonema (Gr. Protos - First, Nema - Thread)
Protonema is a thread-like green body of mosses, from which arise vertical stems with spirally arranged leaves consisting of a single layer of cells.
The protonema is the primary body of mosses, from which perennial stems and leaves subsequently develop. It is a thin green thread consisting of one row of cells. This thread can branch and form a small thallus-like thallus.
Protonema cells form buds that give rise to vertical stems of moss. These stems bear the spirally arranged leaves characteristic of a mature moss plant. Thus, protonema is a transitional stage from a unicellular moss outgrowth to a multicellular thallus and then to moss with a differentiated stem and leaves.