Socio-economic factors contribute to shaping patterns in the species richness of the living collections of the world's botanic gardens.

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A number of papers show the formation of a new membrane on the surface of protoplasm run out after cutting of Characeae alga cells in a medium containing bivalent cations.The drops of isolated protoplasm were prepared by cutting of Nitella cells in a special decompression chamber under the conditions of turgor pressure compensation. The drops were transferred into agar microcapsules (Fig. 1), the preparation of which was described in detail earlier (Salyaev, 1968). The walls of agar microcapsule were transparrent therefore protoplasm drops were clearly observed in a light microscope (Fig. II). All other operations such as fixation, dehydratation and embedding in epoxy resins were made in agar microcapsule.Electron microscopic investigation revealed that the method of a drop preparation preserved all components of a protoplasmic ultrastructure: endoplasmic reticulum, ribosomes, mitochondria etc., the hyaloplasm being rather hydrated (Fig. III). The surface of isolated protoplasmic drop was shown to be a typical membrane 80-90Åthick (Fig. IV).

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