The sporophyte generation produces many small, brown sori on the lower surfaces of the leaves. If the spores produced in these sori fall to a favorable warm, moist medium, they will grow into the gametophyte generation of sperm and egg producing plants. When egg and sperm of the gametophytes fuse, this gives rise to the new sporophyte generation. The indoor ferns are all of tropical origin. They include epiphytes and terrestrial ferns.
Many ferns produce rhizomes which increase the size of the clump of plants and act as propagules.
The plants known as asparagus fern and artillery fern are not true ferns. The genus Adiantum includes the maiden hair ferns . They are often found near streams and thrive in wet soil rich in organic matter and benefit from very high humidity and mists on their leaves. Asplenium nidus is the bird's nest fern . It produces wide fronds that are not subdivided into leaflets.