Correct option (b) brad
Explanation:
Heterospory and seed habit are discussed mostly with respect to ligule. Development of two types of spores (microspores and megaspores) is called heterospory. Though all seed-bearing plants are heterosporous, it evolved in some pteridophytes. In early heterosporous plants, megaspores were released from the parent.
But in seed plants, these are retained and fertilised to become seed. This habit is seen in Selaginella which bears a small multicellular scale-like structure called ligule at the base of leaf on adaxial side.
