Which one of the following is a correct statements?

Some pteridophytes like Selaginella and Salvinia are heterosporous as they produce two kinds of spores micro (small) spores and macro (large) spores, which 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 gametophyte. This event is the precursor to the seed habit, considered to an important step in evolution.