Question

In Dryopteris, the sori are borne
A. Laterally
B. Abaxially
C. Adaxially
D. Marginally

Answer 1

Dryopteris is a fern genus that belongs to the family Dryopteridaceae, and they are commonly known as wood ferns, male ferns, or buckler ferns. These species are distributed in Asia, America, Europe, and Pacific islands with a large diversity in Eastern Asia.

Complete answer:
According to the Pteridophyte Phylogeny Group classification, these ferns are placed in the family Dryopteridaceae. These species are with the highest diversity in eastern Asia. There about 300-400 species are present in the genus Dryopteris (i.e. male shield fern). These ferns are found in moist shady places in tropical, subtropical, and temperate regions.
In Dryopteris, the leaf base possesses an adventitious bud, while the lamina is bipinnate (completely or incompletely). Fers multiplied vegetatively by fragmentation of the rhizome and the development of adventitious buds. These adventitious buds present at the leaf base separates and grows into a new plant.
Leaflets of a mature leaf bear yellowish-brown spots or mass with having clusters of sporangia on the underside (or abaxial surface) of a fertile frond known as sori, and leaflets, and leaves carrying sori or sporangia are called sporophylls. Many of the species have stout, slowly creeping rootstocks which form a crown with a vase-like ring of fronds. In ferns, sori develop in two rows, one on either side of the midrib, and each row contains four to six sori except in smaller leaflets which have one to two sori or can be sterile. Each of the sori is covered by a membranous sheath of its own and this covering is known as true indusium, and these covered sori of Dryopteris are kidney-shaped in the outline and this characteristic has given the name of male shield fern to Dryopteris.

Hence, the correct answer is option (B).

Note: In some species of ferns, sori are protected during the development by a film of tissue known as an indusium which forms an umbrella-like cover. These sori occur in the sporophyte generation, sporangia within producing haploid meiospores. When sporangia mature, indusium shrivels so that spore release is unimpeded, and the sporangia then bursts and releases out the spores.