Statement I is incorrect: Equisetum is a homosporous pteridophyte with a free-living gametophyte; retention of the female gametophyte occurs in heterosporous genera like Selaginella and Salvinia. Statement II is correct: Ginkgo is a gymnosperm, and in gymnosperms, the male and female gametophytes do not have an independent free-living existence. Statement III is incorrect: The sporophyte in mosses (Polytrichum) is more elaborate than in liverworts (Marchantia). Statement IV is incorrect: Sexual reproduction in Volvox is oogamous. Statement V is incorrect: While the vegetative phase (plasmodium) of slime moulds lacks cell walls, their spores possess true walls which make them extremely resistant.