Q. Bryophytes and fern allies were most prevalent during early plant evolution; however, many of these plants have been replaced by vascular plants. These "lower" plants possess flagellated sperm that have to swim through an aqueous medium to reach and fertilize eggs. From this information, in what kinds of habitat will you expect these plants to happen when they were abundant? On the other hand, vascular plants became dominant during the invasion of what type of habitat? What structures allowed them to infiltrate this new environment?