Longtitudinal sections are more informative than cross-sections. There are hardly any features in cross-sections which cannot be observed in an identical or even better way in longitudinal sections. Regarding the deepness of the Hartig net, longitudinal sections are even paramount to cross-sections, particularly if the cortical cells enveloped by the Hartig net are oriented in an oblique way (A). The reason is, that in cross-sections several cortical cell rows can appear to have a Hartig net, in spite of only a single row being enveloped. The left part (A) shows a longitudinal section (above) of a periepidermal Hartig around obliquely oriented root cells, in cross-section, a Hartig net is apparent enveloping two rows of cortical cells (below). The right part (A) indicates the situation of a paraepidermal Hartig net in longitudinal section (above); in cross-section two-and-a-half rows of cortical cells are provided with a Hartig net.
The dimensions of tannin cells are extremely variable depending upon their distance from the root tip, whether they are formed by the outer row or by the second row of root cells, and also regarding the tree genus involved in the formation of ectomycorrhizae. Up to now, only very limited information is available about the influence of the fungus on the shape of tannin cells. The dimensional variability of cortical cells enveloped by a Hartig net however is less than that of tannin cells. To date it seems that the shape of cortical cells in longitudinal sections can at least be used to distinguish some host genera. As it is very time consuming to take these measurements, and since presently these values seem to be of very limited use to distinguish ectomycorrhizae formed by different fungi on the same host, these measurements may be derelicted. But for a complete description of an ectomyorrhiza, somebody might be or might have been inclined to consider the dimensions of these cells, and possibly in the future there might indeed be some differences useful for a delimitation of species.
As longitudinal sections only those sections should be regarded, where the central cylinder with xylem elements can be seen (B–C).
 A |
 B |
 C |