Image Interpretation

 

What are the features labeled A-D? Try and identify the plant stems. How would you distinguish between fungal hyphae, green algal (chlorophyte) and cyanobacterial filaments? What problems are there in identifying these in the Rhynie chert? The scale bar = 2mm.

A: Most likely fungal hyphae.
B: An organic-rich mucilaginous coating binding the plant stems.
C: A partially decayed plant stem.
D: An outer cortex layer.
Plant: Rhynia gwynne-vaughanii
Identification and problems: Fungal hyphae are generally larger, branched and tube-like and may have attached vesicles. Cyanobacteria and green algal filaments are a lot finer and smaller, usually consisting of chains of cells. Cyanobacteria, being prokaryotes, do not contain contain nuclei within their cells and may bear larger heterocysts within the filament chain.

Problems of identification in the Rhynie chert are mainly due to variable degrees of preservation. For example, cell contents may not be preserved; some organic inclusions in cells may be taphonomic artifacts and filaments may just be preserved as ghost structures.