INTRODUCTION. Variability is one of the main characteristics of a living organism. This is what makes them different from unvaried inanimate objects. This characteristic is as important as metabolism, propagation, heredity and others.

The term "variability" is rather vague and is understood in different ways. As a prominent Dutch geneticist and botanist Gugo de Friz said in his work "The Theory of Mutation" (1901): "There is nothing more variable than the meaning of the word "variability". Some authors use it in such a wide sense that you can not understand what they mean".

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Translation Irina Koudina (Okounkova , Mosсow, Russia, e-mail: irinkos2@yandex.ru)