Chapter 21, Problem 24A

Summary Introduction

To write:

The characteristics of ferns.

Introduction:

Pteridophytes are the seedless vascular plants with about 13000 species. They have sporophytic plant body, inconspicuous gametophytes containing small sessile antheridia and partially embedded erchegonia with 4-rowed neck.

Explanation of Solution

The most conspicuous of the pteridophytes are the ferns. Ferns are pteridophytes that bear sporangia in sori on the leaves which show circinate ptyxis in the young condition. The characteristics of ferns are given below.

• Ferns are seedless vascular plants of humid tropics and temperate areas. Some ferns live under sub-arctic conditions as well.
• The plant body is a sporophyte. It is differentiated into true leaves, stem, and roots.
• Roots are adventitious.
• Leaves are large and are known as fronds.
• Leaves possess apical meristem or growing point which, however, stops activity after reaches maturity.
• Sporangia occur on the leaves in clusters named sori. The fertile leaves are called sporophylls.
• Vegetative reproduction occurs by bulbils, adventitious buds, fragmentation of rhizome, etc.
• The gametophyte is thalloid and called prothallyus.
• Sperms are generally multiciliate or multiflagellate.
• An embryo stage is present.

Conclusion

Thus, the ferns are found in in moist environment and they can also survive dry conditions.