DR JEREMY BURGESS / SCIENCE PHOTO LIBRARY DR JEREMY BURGESS / SCIENCE PHOTO LIBRARY
Fruiting plant of the liverwort Marchantia polymorpha subsp ruderalis. The picture shows the upper surface of the receptacles on a male plant. Each is a flattened disc borne above the thallus (green, background) on a stalk about 1cm in length. The receptacle is the site of the antheridia, tissues that produce motile male gametes called spermatozoids. In liverworts, the visible plant is the gametophyte generation, producing male and female gametes. In M. polymorpha, individual plants are either male or female. In the background to this picture, there are many small circular cups on the surface of the thallus. These are gemma cups, and produce small green propagules called gemmae, that are dispersed by rain splash and develop into new plants vegetatively. M. polymorpha ruderalis is a familiar garden weed, particularly on poorly drained soils, and on the soil surface in flower-pots.
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