Fig.
15.3-13a and b. Transverse section of ash (Fraxinus) and apple
(Pyrus malus). The upper
micrograph is ash, with ring porous wood. The arrow marks the
boundary between the latewood of one year and the earlywood of the subsequent
year, and the wide vessels are in the earlywood. notice that after the vascular
cambium produced the wide earlywood vessels, it produced a large amount of
fibers and a few narrow vessels.
The lower micrograph is apple with diffuse porous wood:
the vascular cambium undergoes no dramatic change throughout the entire growing
season, producing only a few less vessels just before it becomes dormant. All
vessels have about the same diameter.