Classification of elongated plant viruses on the basis of particle morphology

Abstract

The length of the particles is the most useful feature for characterizing elongated plant viruses. The characteristic length value of a given virus, calculated as the arithmetical mean from the main maximum of the distribution curve is called "normal length." For electron microscopic preparations the exudate method has been used chiefly. Based upon the results of comparative measurements, a number of elongated viruses are placed in 12 groups according to their normal lengths. Additional characteristics, such as diameter, shape, thermal inactivation point, mode of transmission and serological relationship show correlations within each group and suggest higher systematic units into which viruses with different normal lengths can be combined.