Staining
Tissues place onto microscope slides are usually stained, in order to make identification of various cells and tissues easier. In plant tissues, the walls of xylem cells (tracheids and vessel elements) and sclereids are stained red, while the walls of phloem cells are stained greenish-blue. Other cell types may be harder to distinguish by their staining pattern, but other characteristics such as shape, appearance, and wall thickness may be used for cell identification.
Types of sections for microscope slides
Cross-section: Imagine taking a chainsaw and cutting down a tree. If you look down on the top of the cut stem, you are looking at a cross-section. This is a cross-section of a Pine stem. No vessels are found in in pines and other confers. In this picture, most of what you see is tracheids. There are also a couple of resin ducts (large, circular structures), as well as ray parenchyma (appearing as vertical strands).
Radial section: Radial sections are cut along the radius of the stem. Imagine cutting a wedge out of a tree trunk and looking at the surface of the cut stem. In these sections, rays appear as horizontal sheets. Tracheids appear elongated, with circular bordered pits on their walls.
Tangential section: Tangential sections are cut along the outermost surface. In these sections, tracheids appear elongated, and rays appear appear circular.
