Seed are sometimes sold commercially while still enclosed within the hard wall of the fruit, which must be split open to reach the seed. Different groups of plants have other modifications, the so-called stone fruits (such as the peach) have a hardened fruit layer (the endocarp) fused to and surrounding the actual seed. Nuts are the one-seeded, hard-shelled fruit of some plants with an indehiscent seed, such as an acorn or hazelnut. Seeds are produced in several related groups of plants, and their manner of production distinguishes the angiosperms ("enclosed seeds") from the gymnosperms ("naked seeds"). Angiosperm seeds are produced in
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