Final answer:
Mendelian traits are described as discrete or discontinuous because they are inherited in distinct classes and show discontinuous variation. Mendel's experiments with such traits revealed that they were not blended in the offspring but inherited as distinct traits.
Step-by-step explanation:
Mendelian traits are often described as discrete or discontinuous in nature because they are inherited in distinct classes and show discontinuous variation. Unlike traits that exhibit continuous variation, such as human height, Mendelian traits have easily distinguishable traits, such as the color of flowers. Mendel's experiments with these types of traits demonstrated that they were not blended in the offspring, but rather inherited as distinct traits. This challenged the prevailing belief at the time that inheritance involved blending of parental traits.