Fossil plants systematics

Abstract

Prokaryotes under discussion below involve only bacteria and cyanobacteria (blue-green algae). The classification of living forms of prokaryotes is based on such characters as the configuration of the cells (cylindrical, spiral, spherical, etc.), the mode of their aggregation, mobility, size, mode of feeding, and other features. A character such as the cylindrical form of the cell may occur in combination with any others. Many other characters also combine freely. Because of this the prokaryote system, as was noted by G. A. Zavarzin, assumes the nature of a multidimensional latticework. The nodes of this latticework correspond to taxa, each taxon being defined by a specific combination of characters. Due to the fact that some of the combinations do not occur, missing units occur in the latticework. But the remaining portions of the lattice do not form a structure that may be treated as a phylogenetic tree. In the opinion of G. A. Zavarzin (1974), the construction of a prokaryote system on a phylogenetic basis is, in principle, impossible.