Matthiola Incana

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Abstract
The trisomic form Crenate (7ii + 1ICr), derived from the "double-thrower" variety Snowflake (diploid singles Ss, heterozygosis maintained by non-viability of S. pollen; doubles ss), has been selfed and crossed with pure single (SS or +/ + ), and the results have been compared with expectation on the basis of a two-lethal hypothesis identical, except as to crossing over, with that devised by Haldane and Waddington for diploid double-throwers (Snowflake singles, in the present author''s symbols, l a Sl w/LssLw=l s l w/s; 6% of recombination between s and l w loci assumed, and no recombination between l s and s loci). Normal (7II)F1 hybrids ( + /s) gave ordinary disomic selfing ratios (about 3 single :1 double) in F2. Data from selfing and crossing of Crenate double-thrower singles indicate that they are always Sss; the selfing ratios indicate extensive elimination of the extra chromosome, and suggest both non-random segregation in the trisome and selective elimination of Crenate single. From selfing of Crenate F1, the F2 progenies corresponded well in 3 cases with the expectation for the F1 constitution + /s/s (normals, 5 single:4 double; trisomics, 7 single:2 double), in 1 case with that for + /s/l s l w (5:1 and 1:0), and in 1 case with that for +/s/sl w (2:1 and 5:1). The trisomic form Slender (7II + lISl) carries an extra fragment, which in a CrSl plant often conjugated with the extra Cr chromosome. Ratios from selfing and crossing indicate that the Slender Snowflake singles tested carried only one S, and this more often in the Sl fragment[long dash]conclusions definitely established for one plant by somatic variation; crossing over often transfers the S gene to a whole chromosome. F1 Slenders from crosses with pure single have given at least 3 kinds of selfing ratios (all very unlike those given by Crenate), which correspond well with hypothesis when the deficient constitution of the Sl extra chromosome is considered.