I have
crossed the blue flowered thorny form, usually known as _Datura Tatula_,
with the white thornless type, designated as _D. Stramonium inermis_.
Thorns and blue pigment are obviously active qualities, as they are
dominant in the hybrids. In the second generation both pairs of
characters are resolved into their constituents and paired anew
according to Mendel's law. After isolating my hybrids during the period
of flowering, I counted among their progeny:
128 individuals with blue flowers and thorns
47 individuals with blue flowers and without thorns
54 individuals with white flowers and thorns
21 individuals with white flowers and without thorns
----
250
The significance of these numbers may easily be seen, when we calculate
what was to be expected on the assumption that both characters follow
Mendel's law, and that both are independent from each other. Then we
would have three-fourths blue offspring and one-fourth individuals with
white flowers. Each of these [301] two groups would consist of
thorn-bearing and thornless plants, in the same numerical relation.
Thus, we come to the four groups observed in our experiment, and are
able to calculate their relative size in the following way:
Proportion
Blue with thorns 3/4 X 3/4 = 9/16 = 56.
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