Dispersal is a mechanism where by offspring mature at a location away from the parental plant. Notice the location of the sporangia on the sporophyte. Phloem for seasonal two way flow of water from leaves to roots in summer and from roots to leaves in spring. Presence of lignin a substance which re-enforces cell walls for better support. Once plants became abundant, the competition for light began as light became a limited resource.
Competition increases the strength of natural selection.
However, due to vascular tissue, moisture need only be seasonal for reproduction. Vascular tissue and the roots involved can draw water into the plant from the ground. See figure 29.11 Life cycle of ferns. Notice that the egg is retained in the archegonium, fertilization takes place in the archegonium, sporophyte grows out of the gametophyte. But the Gametophyte is only a few mm across while the sporophyte is quite large.