Consider the following statements regarding heterospory.

(I) Genera like Selaginella and Salvinia, which produce two kinds of spores, macro (large) and micro (small) spores, re known as heterosporous.

(II) The megaspores and microspores germinate and give rise to female and male gametophyte, respectively.

(III) The female gametophytes in these plants are retained on the parent sporophytes for variable periods.

(IV) The development of the zygotes into young embryos takes place within the female gametophytes.

(V) This event is a precursor to the seed habit and is considered an important step in evolution.

Which of the statements given above are correct?