Question

Which of the following is an aquatic fern?
(a)Adiantum
(b)Dryopteris
(c)Salvinia
(d)Equisetum

Answer 1

Hint: Ferns are capable of growing in different environments such as aquatic, terrestrial, epiphytic (growing on trees or tree branches), and epilithic (growing on rock). The aquatic ferns commonly grow in water. The fern belongs to a closely related neotropical species. It is an aquatic weed and is also called Kashmir's sorrow.

Complete answer:
Salvinia is a true aquatic fern with both annual and perennial species ( e.g., S. nutans) (e.g., S. Molesta). The plant body consists of a floating stem bearing on the upper surface two rows of large green hairy leaves, and strongly branched leaf roots on the lower surface.

Additional Information: Adiantum is popularly cultivated as houseplant and garden fern. Dryopteris is generally called wood ferns. Equisetum grows in the fields and is commonly called horsetail.
Salvinia molesta commonly referred to as giant Salvinia, or Kariba weed after ingesting a large portion of Lake Kariba between Zimbabwe and Zambia is an aquatic fern native to south-eastern Brazil.
One suggested usage exploits the hydrophobic trichomes, which do not repel oil. This makes them candidates to mop up oil spills, as in thirty seconds they become contaminated with oil. S. Molesta trichomes served as the basis for similarly hydrophobic polycarbonate synthetics.
So, the correct answer is, ‘Salvinia’.

Note: Water ferns are common around the world in tropical and warm temperate areas, and some are cultivated as plants for aquariums. Even though water ferns often root in mud, they float more often in riverine habitats on the surface of shallow water in ditches, lakes, and stagnant backwaters.