Hornwort thallus cells. Light micrograph of thallus cells from the gametophyte stage of the life cycle of an Anthoceros agrestis hornwort. The gametophyte cells of this plant have one chloroplast (green). The thallus is the macroscopic visible part of a hornwort plant, with the gametophyte stage being the dominant part of the life cycle, in contrast to the spore-producing stage. Hornworts, liverworts and mosses are non-vascular plants collectively known as bryophytes. This sample has been imaged using bright field illumination. Magnification: x715 when printed at 10 centimetres across.