The ferns in which the entire sporangium develops from a single superficial cell of the sporophyll are known as

The young sporophyte of the $Pteris$ fern draws nourishment from the prothallus through:

The antherozoids of Dryopteris are .......

Read carefully the following statements about sexual reproduction in ferns:
$I.$ Water is essential for fertilization.
$II.$ The male gametophyte bears antheridia,while the female gametophyte bears archegonia,which produce antherozoids and egg cells,respectively.
$III.$ Antherozoids and egg cells fuse to give rise to a zygote. The zygote develops into a young embryo. The embryo gives rise to a sporophyte.
Which of the statements given above are correct?

The heart-shaped prothallus of a fern bears:

Which of the following statements is correct?