BOTANY WITH BASICS OF HYDROBOTANY (AQUATIC PLANTS OF UKRAINE) - B.Ye. Yakubenko - 2011

IX. VASCULAR CRYPTOGAMS (PTERIDOPHYTES)

Division Polypodiophyta (Ferns)

Ferns are higher spore-producing plants in which the sporophyte is dominant over the gametophyte, with both generations represented as independent plants.

The sporophytes of extant and fossil ferns include perennial herbs, rarely annuals, and woody plants. Their vegetative body consists of a stem or rhizome, adventitious roots, and large, mostly pinnately compound leaves called fronds. It is believed that fronds evolved from rhyniophyte telomes through flattening or lateral fusion.

Sporangia are located on the leaves, arranged in free groups called sori, or fused into synangia. Most ferns are homosporous. Heterospory is characteristic of the aquatic ferns Marsileidae and Salviniidae.

The gametophyte is monoecious in homosporous ferns and dioecious in heterosporous ones. The vegetative body of the gametophyte is a green thallus with rhizoids, bearing antheridia and archegonia. The spermatozoa are multiflagellate. Water is required for Fertilization.

Ferns originated from rhyniophytes at the beginning of the Devonian period in the Paleozoic era and continue to play a significant role in the Earth's vegetation cover to this day. This division includes about 12,000 species, which are particularly abundant in tropical forests. The Division Polypodiophyta is divided into seven classes:

Class 1 - Aneurophytopsida

Class 2 - Archaeopteridopsida

Class 3 - Cladoxylopsida

Class 4 - Zygopteridopsida

Class 5 - Ophioglossopsida

Class 6 - Marattiopsida

Class 7 - Polypodiopsida

The first four classes are extinct plants. Extant ferns are represented by the classes Ophioglossopsida, Marattiopsida, and Polypodiopsida.

Aquatic ferns are represented by a single class, Polypodiopsida, and the subclasses Marsileidae and Salviniidae.