Rotoxylon

Name

Rotoxylon

Rank

Genus

Authors (Pub.)

Cordi J. Stein W. E.  

Publication

The anatomy of Rotoxylon dawsonii comb. nov. (Cladoxylon dawsonii) from the Upper Devonian of New York State [2005/11]

Journal

International Journal of Plant Sciences

Volume

166

Issue

6

Page number

1031

Year

2005

Parent Taxon

[Phylum] Cladoxylophyta

Fossil Status

stems (wood)

Type

Rotoxylon dawsonii

Diagnosis

Plants comprised of primary tissues only. Vascular tissue dissected. Primary xylem consisting of 18 radially directed and elongate primary xylem ribs. Central connections between primary xylem ribs forming elongate primary xylem segments, variable in size and shape over stem length. Primary xylem maturation mesarch. One permanent protoxylem strand occurring near the tip of each primary xylem rib. Protoxylem tracheids with scalariform secondary wall thickenings. Metaxylem tracheids containing elliptical to elongate bordered pit pairs with elliptical to elongate apertures on all walls. Radial alignment of metaxylem tracheids along lateral edges of some primary xylem segments/ribs. Primary phloem region external to primary xylem segments/ribs. Sieve cells longitudinally elongate with transverse end walls and conspicuous sieve areas. Ground tissue external to primary phloem region containing isodiametric parenchyma with dark lumen contents and longitudinally elongate parenchyma with transverse end walls and clear lumina. Cortex heterogeneous with alternating regions of thick-walled parenchyma and thin-walled parenchyma. Cortical thick-walled parenchyma comprising radially elongate bands in transverse section; typically located between adjacent vascular traces; longitudinally elongate. Vascular traces produced by outward elongation and division of permanent protoxylem strand at tips of primary xylem ribs. Trace departure occurring mostly along midplanes of primary xylem ribs, but some at an oblique angle. Traces in cortex circular in transverse section, containing a single, centrally located protoxylem strand. Trace departure whorled with a regular pattern of angular offset of consecutive whorls.