A botanist discovers a new species of plant in a tropical rainforest. Its characteristics include flagellated sperm, presence of xylem for conducting water, independent gametophyte and sporophyte stages, no seeds. This plant is most likely a

Fern

Explanation:

The plant discovered by the botanist is most likely a fern.

Ferns are referred to as seedless vascular plants. They do not produce seeds and they possess vascular tissues in the names of xylem and phloem. The xylem conducts water/mineral salts from the roots to the body of the plant while the phloem distributes manufactured foods from their sources to other parts of the plant.

Ferns also have independent gametophyte and sporophyte stages. The sporophyte produces haploid spores through meiosis which then germinates to the gametophyte. The gametophyte produces male and female gametes - antheridium and archegonium. The antheridium is motile and swims to meet the immotile archegonium during fertilization to produce the zygote which then divides mitotically to give the sporophyte.