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Primary xylem
Oak wood
Leaf vein
Vein ends
Bean seed
Pine tracheids, xs
Fern TE, xs
Fern, TE, mag
Annular walls
Annular, stretched
Annular, narrow
Scalariform walls
Scalar., narrow
CBP, pine
CBP, dicot
CBP, irregular
Contact faces
Pits, side view
CBP, pine, xs
CBP,angio, xs
CBP, fern, xs
Contact face, xs
Simple perf. plate 1
Simple perf. plate 2
Pitted perf. plate
Perf. plate & helix
Perf. plate, face
Perf. plate, mag
Perf. plate, section
Perf. plate rim
Perf. plate & wall
Scalariform Per plate
Primary xylem
Vessel sizes
Fern TE
Pine needle
VE precursor, ls
Protoxylem
9 Contact faces
VE precursor, xs
Precursor 2
Torn vessel
Torn vessel 2

Fig. 7.2-4. Longitudinal section of fern stem (Pteridium). This micrograph shows excellent scalariform pitting. Each long, horizontal white area is the pit aperture (actually, we are looking through the two apertures of each pit-pair) and the red is the Safranin-stained secondary wall. Note that almost all of the primary wall is covered with secondary wall in a cell like this there is so much secondary wall that the cell is strong enough to provide considerable support to the stem. The two lines pointed out by the arrows indicate the corners of the cell that are not penetrated by the scalariform pits. Because these corners are not pitted, they are especially strong and prevent the cell from being stretched by the surrounding tissues.