ABSTRACT
The Gramineae are defined as monocotyledonous plants that have hollow, or rarely solid, jointed stems and leaves in two rows on stems, with embryos lateral to the endosperm and seeds that are borne between two scales. Such a simple definition characterizes one of the largest and most important families of flowering plants whose origin dates back to the Jurassic period of the Mesozoic era, approximately 130 million years ago (Thomasson, 1986). The uncertainty is due to a lack of a definite grass archetype in the fossil records. Members of the approximately 8000 species occur from forests, forest margins, and cooltemperate open meadows, to open savannas and semiarid tropic and subtropical regions. This present-day distribution is a consequence of several evolutionary lines leading to a diversity of species.
