Above: Straws and partially decayed plant stems held in an open framework of amorphous, 'clotted' sinter. The straw in the centre of the image contains a geopetal layer of sediment and silica cement.  Sinter from Elk Flats, Yellowstone National Park (scale bar = 250µm).

Above: Straws of Aglaophyton and partially decayed plant stems held in an open framework of amorphous, 'clotted' chert. The two straws in this sample of Rhynie chert exhibit similar geopetal textures to that in the modern sinter shown in the image on the left (scale bar = 3mm).

Above: Silicified, partially decayed plant stem missing much of the cortex, the resulting void is traversed by a mesh of silicified microbial filaments. Stream bed sinter near White Dome Geyser, Yellowstone National Park (scale bar = 250µm).

Above: Decayed stem of Aglaophyton with the xylem strand and remainder or the internal cells collapsed to the base of the straw. The resulting void is traversed by a mesh of filaments (probably fungal hyphae) (scale bar = 1mm).

Above: A plant axis that has partially decayed and shrunk away from the cuticle before being silicified. Sinter from Elk Flats, Yellowstone National Park (scale bar = 500µm).

Above: Partially decayed axes of Rhynia gwynne-vaughanii that have shrunken away from the cuticle before being silicified (scale bar = 2mm).