There are many procaryotic and eucaryotic organisms in plant kingdom. It is 
hoped that the study of plant histones will be useful in evolutionary studies. 
The histones of great variety of animal species have been studied and well 
characterized. Less information is available concerning plant histones. The 
general conclusion drawn from these investigations is that most organisms of 
eucaryotic plant and animal species contain the same five major histone 
fractions. Recently the histone-like proteins were found in some primitive 
eucaryotes and procaryotes. Data on histones from higher and lower eucaryotes 
and histone-like proteins of procaryotes are reviewed. Evolution of histones and 
their appearance prior to that of eucaryotic cell is postulated. The role of 
histones in evolution of nucleosomes is discussed.