The gametophyte is a small thalloid structure which shows varying degrees of independence affording an interesting transition to the next group.
In the Lower Carboniferous of Scotland Mr Kidston has found several specimens of a large dichotomous thallus, with a very distinct midrib; the specimens, referred to the provisional genus Thallites, much resemble the larger thalloid Liverworts.
It is true that certain Bryophyta (Marchantiaceae, Anthoceroteae) possess a thalloid structure similar to that of Thallophyta, and are at the same time possessed of the colouring matter of the Green Algae.
The familiar duckweed which covers the surface of a pond consists of a tiny green "thalloid" shoot, one, that is, which shows no distinction of parts - stem and leaf, and a simple root growing vertically downwards into the water.
The prothalli of the Pterido phytes, which form similar symbioses, show a somewhat different mode of arrangement, the Fungi occupying the external or the lower layers of the thalloid body.