I think someone wants to look at the surface of the wood after it has been cut. In that case, it is the cross-section that is of interest.

Wood is the product of the metabolic and physiological activity of woody plants. ... The first type of longitudinal section, the so-called radial one, passes throug
hhttp://www.microscopy-uk.org.uk/mag/indexmag.html?http://www...

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Note added at 2 hrs (2013-12-17 15:39:34 GMT)
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Distribution of Intermediate and Mature Wood on the
Longitudinal Cross Section of the Tree Trunk and Selected
Biometric Traits of Scots Pine (Pinus sylvestris L.)
http://www.balticforestry.mi.lt/bf/PDF_Articles/2007-13[1]/116_125%20Tomczak%20et%20al.pdf

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Note added at 2 hrs (2013-12-17 15:42:59 GMT)
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The most important is the so called transversal surface, it corresponds to the face of the trunk which you can see at the end of a cut plant. It can be easily recorded in a wood piece because of the visibility of the growth rings. The other two cutting plans for wood orientation are longitudinal: they follow the cells orientation in the trunk. The first type of longitudinal section, the so-called radial one, passes through the pith: the centre of the trunk. The second type, the tangential section does not cross the pith, but it is a tangent of the growth rings.
http://www.microscopy-uk.org.uk/mag/indexmag.html?http://www...