Softwood Structure

TRACHEIDS

A. 90-95% of wood (xylem) volume

B. 100 times longer than wide (3-4 mm by 0.025 - 0.045 mm)

C. rectangular cross section

D. end -- rounded radially and pointed tangentially

                see page 69 in textbook

PITTING

A. all on radial face

B. bordered between tracheids

C. half-bordered between tracheids and rays

D. western redcedar doesn't have tori (plural of torus)

ASPIRATED PITS

A. appears to be a permanent condition

B. results of liquid tensions

C. more common during transition from sapwood to heartwood

D. More in earlywood than latewood

                see page 71 in textbook

EPITHELIUM

resin canals -- assist in identification

separation at the adjoining corners of several undifferentiated longitudinal cells. Surrounding cells do not develop normally but develop crosswalls and become resin-secreting cells called epithelial.

resin is used to ward-off insects or other would be invaders or seal off an area of injury (traumatic resin canals)

        see Figures 4.6. and 4.7. on pages 73-74 in textbook

RAYS

horizontal orientation

ray parenchyma & ray tracheids

dentate ray tracheids -- cell wall thickenings around pits

fusiform ray -- ray containing a resin canal.

LONGITUDINAL PARENCHYMA

usually longitudinal strands of short cells butted end to end