The potato virus "X": Its strains and reactions

The virus, the subject-matter of the following study, is known under several names: theX virus of Dr Kenneth M. Smith (1931), the common mosaic of Quanjer (1923), the healthy potato virus of Johnson (1925), which he also called tobacco ringspot (a name now given to a quite distinct virus, viz. that described by Wingard (1928) and others (Thung, 1936), and potato virus 1, the name now given by Smith (1937). The extensive work which Smith, the writer and his colleagues, have done on this virus during the last four years has led to the appellation of the X virus being generally adopted as the most convenient, as well as the least committal, of its synonyms, and it is the one which will be adhered to in this paper. Smith drew attention to the variation in virulence of the symptoms exhibited by the virus infection he then called tobacco ringspot, induced by the inoculation of the juice of a potato suffering from what appeared to be simple mosaic.