Viper tongues

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The viper tongues (Ophioglossum) are a genus of ferns from the family of viper tongues (Ophioglossaceae).

Description
Like all plants in the family, the viper tongues have one or a few base leaves that spring from an underground, short stem. The leaves are divided to the ground or at least far down into two sections, a flat, sterile “spread”, the trophophyll, which is usually called “the leaf”, and a fertile part, the sporophyll.

The trophophyll is always undivided and complete in the viper tongues. From the form it is tongue-shaped, lancet-like, to heart-shaped. Its reason includes the sporophyll, so that at first glance the two leaf parts often seem to separate far above the ground. The flat part of the trophophyll can be seated or stalked. Its size varies considerably among the different species.

The mesh-like nervous nature of the trophophylls seems to indicate that the viper tongues are a derived group rather than an original group of ferns.

The not always present sporophyll is always long stalked. The sporangia are arranged on it in two vertical rows and are laterally overgrown, so that it seems as if they have been sunk into the sporophyll. The latter is narrowly linear and ends more or less acutely in most species.

In most species in temperate latitudes only a single leaf is formed per year, in tropical representatives of the genus sometimes up to five.

Dissemination and location claims
The genus is distributed worldwide, with most species occurring in the tropics and subtropics.

All but two species grow viper tongues on wet to wet soil on grasslands. They are probably often overlooked, because in a sterile state they look similar to the cotyledons of single-germ leaves.

The two species not mentioned growing on earth are Ophioglossum pendulum and Ophioglossum palmatum. These grow epiphytically and deviate a lot from the other species in habitus, which is why they are often called Ophioderma pendula or Ophioderma pendula. Cheiroglossa palmata can be divided into its own monotypical genera.

Species
The genus covers between 20 and 50 species worldwide.

European species
There are four species in Europe:
Ophioglossum azoricum: It is found in the Azores, Canary Islands, Madeira, Portugal, Spain, France, Great Britain, Iceland, Ireland, Italy, Corsica and Poland.
Ophioglossum lusitanicum: It is found in the Azores, Canaries and Madeira, Morocco, Algeria, Tunisia, Tanzania, Uganda, Portugal, Spain, France, Great Britain, Italy, Croatia, Greece, Albania, Cyprus, Near East Asia, Azerbaijan and Georgia.
Ophioglossum polyphyllum, occurs in Africa and Southwest Asia, but also in the Canary Islands.
Ordinary viper tongue (Ophioglossum vulgatum), comes in almost all of Europe,