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Implicit in the concepts of Bailey (1944) and the tabular data on bordered pits by Metcalfe & Chalk (1950, xlv) is the idea that the tracheid is the primitive (plesiomorphic) type of imperforate tracheary element in angiosperms, and that it has evolved, in'evcrsibly, into fiber-tracheids in various clades, followed by libriform fibers.
Carlquist (1988) described the imperforate tracheal elements of Catha, Elaeodendron, Celastrus and Maytenus as septate libriform fibres, septate fibre-tracheids and vasicentric tracheids.
Vessels and a parenchyma cells are embedded in a tissue consisting of thin-walled libriform wood fibres.
High degree--rupturing wood cell pore membranes, resin boiling and replacement, destroying tyloses (in hardwood species), rupturing ray cells, rupturing main cell (traheids, libriform, parenchyma) walls and walls of vessels, and formation of cavities being primarily in radial--longitudinal planes.
These cells have been reported to be libriform fibers, but SEM study reveals small borders (Fig.
For example, the diameter of the largest vessel elements of Populus tremuloides, one of the typical wood species used in OSB production, is 50 [micro]m to 100 [micro]m; and its libriform fibers are 20 [micro]m to 30 [micro]m (Panshin and deZeeuw 1980).
The wood presents extremely short vessel elements, with alternate areolate punctuations, and simple perforated plates, vasicentric axial parenchima, confluent stripes, uniseriated rays, extremely short, fine and very short libriform fibres.
For example, rather than representing "noise" and "aberrations", it seems just as plausible that selection should favor very high variation in features such as libriform fiber length; high variability in length could be favored by selection in that it would diminish the occurrence of fracture planes that would result if cells were aligned, while still resulting in mechanical and hydraulic characteristics that meet the needs of the stem given its size.
However, maple contains areas of libriform fibers with large diameters that may influence the local SG and this may affect lateral and principal forces due to a density gradient.
These species have diffuse porosity, alternate vessel pits, simple perforation plates, numerous and small rays; libriform fibres are common, as well as ergastic material in gum forms, calcium carbonate and silica crystals.
For imperforate elements, is the Baileyan pattern of true tracheids transforming to fiber-tracheids and then to libriform fibers the only transformation series, or is there evidence of other evolutionary patterns?