Hymenophyllum is a genus of ferns in the family Hymenophyllaceae. Its name means "membranous leaf", referring to the very thin translucent tissue of the fronds, which gives rise to the common name filmy fern for this and other thin-leaved ferns. The leaves are generally only one cell thick and lack stomata, making them vulnerable to desiccation. Consequently, they are found only in very humid areas, such as in moist forests and among sheltered rocks. They are small and easy to overlook.
Trichomanes is a large genus of ferns in the family Hymenophyllaceae, termed bristle ferns.Some botanists place it in its own family, Trichomanaceae. All ferns in the hymenophylloid clade are filmy ferns, with leaf tissue typically 2 cells thick. This thinness generally necessitates a permanently humid habitat, and makes the fronds somewhat translucent.
The name bristle fern refers to the small bristle that protrudes from the indusia of these ferns.
At least one species now is known to exist solely in its gametophytic stage. Trichomanes intricatum has no known sporophytes and is native to eastern North America.
Crepidomanes is a genus of ferns in the family Hymenophyllaceae.
Credit for Descriptions to -Wikipedia