436 BROOKLYN BOTANIC GARDEN MEMOIRS 
tion to the expected ratios. In families No. 15405 and 15406, which 
were given the most careful and detailed study, there was little evi- 
dence of the suppression of dominant characters, except that in a 
few specimens it was a little difficult to be quite sure whether the 
A lobe was present or not and it is not improbable therefore that a 
few heteris plants have been erroneously included in the rhomboidea 
group, but this does not affect the ratios relative to the presence or 
absence of the B factor. On the whole, the three families derived 
from F, plants of pedigree 14378, showed the least marked tendency 
to the suppression of the dominant lobing, and these families show a 
close approximation to the expected ratio 45 AB :15aB:3 Ab:1ab. 
The close agreement with this ratio in these families, indicates not 
only the duplication of the B factor but also the independence of the 
two B factors from the A factor. 
While 15:1 ratios in the F, give evidence of duplication, it is 
highly important to carry the analysis forward at least into the F3 
generation in order to secure more convincing proof that the B factor 
was really duplicated in the dominant parent of the original cross. 
Until now the only families beyond the Fz which have been grown from 
material in which the B factor is duplicated, have been derivatives 
from the earlier Tucson cultures and, as before, these families were 
grown primarily for the study of the capsules, and only incidental 
attention was given to the rosettes. The ratios in these families are 
also defective, therefore, but they give, nevertheless, strong support 
to the hypothesis that the B factor is duplicated in the Tucson plants. 
These F; families are brought together in Table 5. 
This table has been arranged into the three groups which are 
expected in the Fs; of a cross involving duplication of determiners. 
In the first section are the families which bred true to the B lobing; 
in the second section are those which split in the ratio 15 : I, and in 
the third section are those which split into 3:1. The results may be 
summarized as follows: 19 F; families contained neither tenuis nor 
simplex individuals, seeming to indicate that the I9 parents of these 
had at least one of the B factors homozygous; 3 families showed 
ratios which may be assumed to represent the 15 : 1 class, showing 
that the 3 parents of these had both B and B’ present in the hetero- 
as probably having a duplication of the B lobe. As stated in footnote to Table 1, 
15: 1 and 3:1 ratios might both occur in the F: families grown from plants in a 
single F, family, if the wild form used in the cross happened to be heterozygous for 
one or the other of the B factors. Thus 
BBB'b’ X bbb’b’ = BbB’'d’, yielding 15 : 1, and Bbb’b’ yielding 3 : I. 
This situation appears to have been realized in two cases, involving F, families 
14357 from Wales and 14368 from Berlin. These two crosses are included in both 
Tables 1 and 4. 
