Selaginella and Salvinia are considered to represent a significant step towards evolution of seed habit…
Selaginella and Salvinia are considered to represent a significant step towards evolution of seed habit because
female gametophyte is free and gets dispersed like seeds
female gametophyte lacks archegonia
magaspores possess endosperm and embryo surrounded by seed coat
embryo develops in female gametophyte which is retained on parent sporophyte
Solution
Selaginella and Salvinia are heterosporous as they produce two kinds of spores-mirco (small) spores and macro (large) spores. The microspores and megaspores germinate and give rise to male and female gametophyte, respectively. The female gametophyte in these plants are retained on the parent sporophytes for variable periods. The development of the zygotes into young embryos takes place within the female gametophytes. This event is the precursor to the seed habit considered to an important step in evolution.