Protonema (pl. protonemata) The young bryophyte gametophyte that develops following spore germination. The mature gametophyte plants develop from buds that form at several points along the protonema.

• 原丝体：苔藓植物中直接由孢子萌发形成的结构称为原丝体。原丝体上形成1个或几个芽体，芽体进一步发育为配子体。