Gould (1968) has divided the family of grasses (Gramineae) into 25 tribes and 177 important genera. Seed dormancy occurs within 18 of the tribes and has been recorded in one or more species in at least 78 of the genera (Table 1.1). Seed dormancy is one of a number of adaptive traits, such as seed size and shape, that are polymorphic in character. Together these characteristics provide diversity and fitness for both opportunistic settlement and enduring occupation of temporally and spatially diverse habitats (Jain & Marshall, 1967). Within each grass species there can be considerable variation in the degree of polymorphism associated with the expression of seed dormancy. The degree of polymorphism is a function of the form of reproduction (self– or cross– pollination) in each species. Some species rely on genetic diversity and others on phenotypic plasticity for adapting to varying environments through the trait of seed dormancy.