Psilotopsida

Psilotum nudum

The class includes two rather unequal Psilotopsida plant families, the fork -leaved plants and the adder's tongue plants.

Features

The relationship between the two families has been elucidated only in recent years with molecular biological methods, as both families have simplified morphological structures.

The reduction of the root system is a common feature in the fork blade plants the roots are missing at all. The gametophytes live underground, are not photosynthetically active and have a mycorrhiza. The sporangia sit adaxial ( toward the stem axis ), and they develop eusporangiat ( the sporangium has several cell layers ).

System

The fork blade -like are the sister group of all other ferns. From the fork blade plants no fossils are known, the adder's tongue plants are in the fossil record only since the late Paleocene ( Botrychium wightonii ). There are only about 100 species in six genera.

• Order adder's tongue -like ( Ophioglossales ) Family adder's tongue plants ( Ophioglossaceae ) with about 80 species in four genera

• Family Fork -leaved plants ( Psilotaceae ) with 12 species in two genera