A diffuse-porous arrangement of vessels; scalariform
perforation plates; scalariform
intervessel pits; vessel-ray pits with much reduced borders to apparently simple; vessel-ray pits rounded or angular; vessel-ray pits horizontal (scalariform
, gash-like) to vertical (palisade); tyloses in vessels; septate and non-septate fibres with simple to minutely bordered pits; fibres very thick-walled (Figure 5); scanty paratracheal axial parenchyma; aliform axial parenchyma; unilateral paratracheal axial parenchyma; larger rays commonly 4 to 10 seriate; body ray cells procumbent with one row of upright and/or square marginal cells; prismatic calcium oxalate crystals in upright and/or square ray cells and also in procumbent ray cells.
Cheadle (1942) also offers some gradate phylogenetic progressions, based mostly on the end walls of vessel elements: long scalariform
perforation plates are considered indicative of "primitive" conditions, simple perforation plates are considered at the opposite extreme, indicators of specialization.
The particles presented hollow-spheroid-like shape and the surface micro-structure was scalariform
The xylem showed incurved margins and consists of scalariform
tracheids and parenchyma cells.
Resistances to fluid flow of model xylem vessels with simple and scalariform
tracheids attached to Artisia (his Sternbergia) pith casts, Dawson assumed that at least some of these fossils must have belonged to Sigillaria, based on the common occurrence of scalariform
tissue in that plant (Dawson 1859).
The pits are present in opposite or scalariform
The seed coats are moderately or deeply reticulate with layers of scalariform
thickenings on the radial walls.
The polarity of the tracheid-vessel transition and that from tracheid-like vessel elements that were long and narrow with scalariform
pitting and perforation plates to short, wide elements with alternate pitting and simple perforation plates was then used to anchor inferences regarding a suite of other characters in the wood given their association with vessels of a given "level of specialization" (Table 1).
One example is the assemblage from Svanta Savane, a site in the lowlands, rich in scrapers with scalariform
retouch and high frequencies of burins on truncations.
Under SEM macerated tracheary elements from roots, rhizomes and leaf rachises showed large scalariform
perforations lacking pit membranes, thus constituting apparent perforation plates.
Protoxylem tracheids, 6-12 [micro]m in diameter, are characterised by annular and spiral thickening with scalariform
and transitional pitting seen on the 9-15 [micro]m diameter metaxylem tracheids (Fig.