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PALAEOBOTANICAL RESEARCH   GROUP
 
UNIVERSITY  MÜNSTER

THE   RHYNIE  CHERT  AND  ITS  FLORA

 
VI. GROWTH   FORMS  OF  AGLAOPHYTON  AND  RHYNIA
 
 
 
 
Whereas single individuals of Aglaophyton major with their creeping axes could already occupy larges surfaces, Rhynia gwynne- vaughanii had a more thicket-like to bushy appearance.  The specimen illustrated at left shows numerous very densely standing axes.  The axes of this leafless plant bifurcated only occasionally but they borne many lateral axes.  These lateral axes were occasionally dropped off, being a mode of vegetative propagation.  Only the basal parts of the axes were lying directly on the substrate.  All more distal parts of axes were standing upright.  It is very remarkable that also upright standing aerial axes frequently have rhizoids, obviously for taking up atmospheric water. Plants like Rhynia probably had real difficulties taking up sufficient water.  Both the symbiosis with vesicular arbuscular mycorrhizae and the presence of rhizoids on the aerial shoots were certainly advantageous. Also the bushy growth form might have been beneficial because axes shaded each other and only few axes were exposed to direct sunlight thus reducing the risk of excessive evapotranspiration.  Rhynia occurred on various substrates, ranging from siliceous rocks to sandy soils (see the picture left below). In the sandy soil seen an the picture at left organic detritus can be recognized as thin black layers: higher land plants had started to contribute to the formation of soils !  
Left above: A piece of chert with numerous densely standing axes of Rhynie gwynne- vaughanii.  The dark rings vaguely visible in the axes shown in the enlargement are VAM. 
Left below: The same piece of chert as shown at left above but now seen perpendicularly to the bedding plane showing the upright standing axes on a sandy substrate with organic detritus (soil).


© Forschungsstelle für Paläobotanik, Westfälische Wilhelms-Universität Münster 
April 2000