A Method for Determining Tracheid Lengths in Petrified Wood by Analysis of Cross Sections

A method is presented for estimating the length of tracheidsin fossilized secondary xylem by analysis of intersected cellsin cross sections. A two-dimensional model depicting cell positionin wood is used to derive an equation which relates the totaltracheid length to the length of the tracheid apex and the ratiobetween the number of intersected tracheid shafts and apicesobserved in cross section. Use of the technique is demonstratedin an investigation of the wood of Sphenophyllum plurifoliatum,an anatomically preserved Carboniferous arthrophyte with extremelylong tracheids. The values obtained in the analysis correspondclosely to lengths determined by indirect measurement. An examinationof the assumptions on which the method is based reveals thatthe accuracy of the cell length estimates will vary accordingto the shape of area being analysed and intrinsic structuralfeatures of the wood. Sphenophyllum plurifoliatum, Carboniferous, plant fossil