Then , the first tracheids of the transition zone are formed , where the radial size of cells and thickness of their cell walls changes considerably .
The tracheids of earlywood formed at the beginning of a growing season have large radial sizes and smaller , thinner cell walls .
The first tracheids of the transition zone are formed , where the radial size of cells and thickness of their cell walls changes considerably .
The tracheids of earlywood formed at the beginning of a growing season have large radial sizes and smaller , thinner cell walls .