Kuksonia

Discovered in 1937 in the Silurian sandstones of Scotland (age about 415 million years). Later, kuchsonia was also found in the Upper Silurian deposits of Czechoslovakia , the USSR ( Podolia and Central Kazakhstan ) and the USA ( New York State ), as well as in the Lower Devonian of Western Siberia ^[4] .

Compared to other representatives of the flora of that time, Cuxonia were very developed organisms. They consisted of branching green stems with single sporangia of a bulbous shape at the apex, not more than 5 cm high. The stems branched in the most primitive way - dichotomously. The breeding of the Kuxonians was carried out by disputes . Attached to the ground with the help of rhizoids . Most likely, they were annuals and grew in water. Cuxonia acquired cuticles, this peel protected the plant from water loss, in addition, they had special stomata in a wax shell, which allowed them to make gas exchange and control evaporation , and also, if necessary, to consume nutrients from the environment .

Kuksonia is the earliest of the studied forms of plants that had primitive adaptations that allowed them to survive under the scorching sun. Soil at that time did not exist. In addition, at that time the Earth’s atmosphere was different from the modern one, therefore all living things on land were subjected to increased exposure to ultraviolet rays . Most likely, kuksonia grew in a swamp, the water in which contained silicic acid , and the plant residues, saturated with salts of this acid, were able to preserve the finest microstructure of tissues.

These plants were not pioneers of land ^[6] . Before them, the rocks and sands of the ancient continents covered the layered settlements of bacteria - bacterial mats , as well as lichens , fungi and algae , which prepared the ground for the first land plants.

Scientists have not come to an unambiguous conclusion about the position of kuchsonia on the phylogenetic tree of plants. Initially, the genus was included in the rhinophyte department. Since the end of the 20th century, it occupies an indefinite position ( incertae sedis ) among vascular plants ^[5] .