When two constant species of Nicotiana are crossed, the hybridization, if successful, gives a uniform F1 exhibiting unmistakable hybrid characteristics. There have, however, been sporadic reports of the production of occasional plants in interspecific hybridization in Nicotiana which differ from the expected hybrid type. Manifestly some of these results have been due to error, dependent particularly on the use of parent species one or both of which have not been constant; but it is difficult to explain all the reports in this way.During the season of 1923 two plants were obtained which were outstanding exceptions to the general rule of uniformity of F, interspecific progenies. Both occurred in F1 progenies of Nicotiana Tabacum 9 X N. sylvestris c<. As a rule this cross gives a uniform, vigorous, nearly completely sterile F1 hybrid which is a replica on an enlarged scale of its particular Tabacum parent (cf. Goodspeed and Clausen, 1917 a and b). Two such hybrid progenies grown in 1923 gave the usual results, except that in each population one exceptional plant appeared which was a replica on a reduced scale of its immediate Tabacum parent. Both of these plants had 24 chromosomes. Since the chromosome number in Tabacum is n = 24 (White, 1913) and in sylvestris n = 12 (Goodspeed, 1923), the exceptional plants were evidently Tabacum haploids. One of these exceptional plants appeared in an F1 of N. Tabacum var. purpurea 9 X N. sylvestris 6<. Among 58 plants grown, 57 were of the expected hybrid type. The exceptional plant was obviously a reduced replica of purpurea. It exhibited all the differential characters peculiar to purpurea; but the expression of the characters was somewhat exaggerated. This exaggeration of purpurea characters was particularly evident in the leaf base, which in purpurea is sharply constricted almost to the midrib.
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