Evolutionary history of plants phloem on the outside. Since xylem cells comprise dead, lignified tissue, subsequent rings of xylem are added to those already present, forming wood. The first plants to develop secondary growth and a woody habit, were apparently the ferns, and as early as the Middle Devonian one species, "Wattieza", had already reached heights of 8 m and a tree-like habit. Other clades did not take long to develop a tree-like stature. The Late Devonian "Archaeopteris", a precursor to gymnosperms which evolved from the trimerophytes, reached 30 m in height. The progymnosperms were the first plants to develop true wood, grown from
Botanical Garden named after Rostovtsev and a botanical garden was headed by Professor V. G. Khrzhanovsky. When it was built a greenhouse for subtropical plants. At present, on the basis of the botanical garden, summer scientific research and production practice is conducted. Students study there ways of plant reproduction, morphogenesis, as well as technologies of landscape design. Periodically free excursions are organized for all comers. In the botanical garden there are landscapes, ornamental and experimental sites, as well as a greenhouse with an area of about 400 m². According to data for 2012, in the botanical garden there are about 600 species and forms of