Mature stems of 2 genotypes selected for high and low digestibility were used. The quantification was used to localise the stem portion showing maximum variation. Quantitative measurement of histological characters was carried out on stained cross sections using image analysis. Three stems per genotype were evaluated for histological characters and the rest of each genotype was used to determine NDF and Klason lignin content. Stems within each genotype did not show any significant differences. The 2 genotypes were significantly different for cortex thickness, cortex area, xylem vessel area, xylem fibre area, xylem cell wall density, and xylem cell wall thickness. The maximum variation for histological characters was observed at the stems base to facilitate the sampling to assess genetic variation. In future studies the available genetic variability for histological characters will be analysed within and among varieties in dense conditions.