Mendel's principles of heredity: A defenceMendel, Gregor
Science
Mendel's principles of heredity: A defence
Mendel, Gregor
Heredity; Hybridization; Mendel's law; Weldon, Walter Frank Raphael. Mendel's laws of alternative inheritance in peas
With regard to this last character it must be stated that the longer
of the two parental stems is usually exceeded by the hybrid, which is
possibly only attributable to the greater luxuriance which appears in
all parts of plants when stems of very different length are crossed.
Thus, for instance, in repeated experiments, stems of 1 ft. and 6 ft.
in length yielded without exception hybrids which varied in length
between 6 ft. and 7-1/2 ft.
The hybrid seeds in the experiments with seed-coat are often more
spotted, and the spots sometimes coalesce into small bluish-violet
patches. The spotting also frequently appears even when it is absent as
a parental character.
The hybrid forms of the seed-shape and of the albumen are developed
immediately after the artificial fertilisation by the mere influence of
the foreign pollen. They can, therefore, be observed even in the first
year of experiment, whilst all the other characters naturally only
appear in the following year in such plants as have been raised from
the crossed seed.
THE FIRST GENERATION [BRED] FROM THE HYBRIDS.
In this generation there reappear, together with the dominant
characters, also the recessive ones with their full peculiarities,
and this occurs in the definitely expressed average proportion of
three to one, so that among each four plants of this generation three
display the dominant character and one the recessive. This relates
without exception to all the characters which were embraced in the
experiments. The angular wrinkled form of the seed, the green colour of
the albumen, the white colour of the seed-coats and the flowers, the
constrictions of the pods, the yellow colour of the unripe pod, of the
stalk of the calyx, and of the leaf venation, the umbel-like form of
the inflorescence, and the dwarfed stem, all reappear in the numerical
proportion given without any essential alteration. _Transitional forms
were not observed in any experiment._
Once the hybrids resulting from reciprocal crosses are fully
formed, they present no appreciable difference in their subsequent
development, and consequently the results [of the reciprocal crosses]
can be reckoned together in each experiment. The relative numbers
which were obtained for each pair of differentiating characters are as
follows:
Expt. 1. Form of seed.--From 253 hybrids 7,324 seeds were obtained in
the second trial year. Among them were 5,474 round or roundish ones
and 1,850 angular wrinkled ones. Therefrom the ratio 2·96 to 1 is
deduced.
Expt. 2. Colour of albumen.--258 plants yielded 8,023 seeds, 6,022
yellow, and 2,001 green; their ratio, therefore, is as 3·01 to 1.
Public-domain text, read in full here on John Shaqi.
Reviews
Reviews
No reviews yet
Be the first to share your thoughts on this work.
Join the Discussion
Join the discussion
Sign in to leave a comment or review.
Sign InorCreate an account