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.
In these two experiments each pod yielded usually both kinds of seed.
In well-developed pods which contained on the average six to nine
seeds, it often occurred that all the seeds were round (Expt. 1) or
all yellow (Expt. 2); on the other hand there were never observed more
than five angular or five green ones in one pod. It appears to make no
difference whether the pods are developed early or later in the hybrid
or whether they spring from the main axis or from a lateral one. In
some few plants only a few seeds developed in the first formed pods,
and these possessed exclusively one of the two characters, but in the
subsequently developed pods the normal proportions were maintained
nevertheless.
As in separate pods, so did the distribution of the characters vary in
separate plants. By way of illustration the first ten individuals from
both series of experiments may serve[34].
[34] [It is much to be regretted that Mendel does not give the
complete series individually. No one who repeats such experiments
should fail to record the _individual_ numbers, which on seriation
are sure to be full of interest.]
Experiment 1. Experiment 2.
Form of Seed. Colour of Albumen.
Plants. Round. Angular. Yellow. Green.
1 45 12 25 11
2 27 8 32 7
3 24 7 14 5
4 19 10 70 27
5 32 11 24 13
6 26 6 20 6
7 88 24 32 13
8 22 10 44 9
9 28 6 50 14
10 25 7 44 18
As extremes in the distribution of the two seed characters in one
plant, there were observed in Expt. 1 an instance of 43 round and only
2 angular, and another of 14 round and 15 angular seeds. In Expt. 2
there was a case of 32 yellow and only 1 green seed, but also one of 20
yellow and 19 green.
These two experiments are important for the determination of the
average ratios, because with a smaller number of experimental plants
they show that very considerable fluctuations may occur. In counting
the seeds, also, especially in Expt. 2, some care is requisite, since
in some of the seeds of many plants the green colour of the albumen is
less developed, and at first may be easily overlooked. The cause of the
partial disappearance of the green colouring has no connection with the
hybrid-character of the plants, as it likewise occurs in the parental
variety. This peculiarity is also confined to the individual and is
not inherited by the offspring. In luxuriant plants this appearance
was frequently noted. Seeds which are damaged by insects during their
development often vary in colour and form, but, with a little practice
in sorting, errors are easily avoided. It is almost superfluous
to mention that the pods must remain on the plants until they are
thoroughly ripened and have become dried, since it is only then that
the shape and colour of the seed are fully developed.
Expt. 3. Colour of the seed-coats.--Among 929 plants 705 bore
violet-red flowers and grey-brown seed-coats; 224 had white flowers
and white seed-coats, giving the proportion 3·15 to 1.
Expt. 4. Form of pods.--Of 1,181 plants 882 had them simply inflated,
and in 299 they were constricted. Resulting ratio, 2·95 to 1.
Expt. 5. Colour of the unripe pods.--The number of trial plants was
580, of which 428 had green pods and 152 yellow ones. Consequently
these stand in the ratio 2·82 to 1.
Expt. 6. Position of flowers.--Among 858 cases 651 blossoms were
axial and 207 terminal. Ratio, 3·14 to 1.
Expt. 7. Length of stem.--Out of 1,064 plants, in 787 cases the
stem was long, and in 277 short. Hence a mutual ratio of 2·84 to
1. In this experiment the dwarfed plants were carefully lifted and
transferred to a special bed. This precaution was necessary, as
otherwise they would have perished through being overgrown by their
tall relatives. Even in their quite young state they can be easily
picked out by their compact growth and thick dark-green foliage.
If now the results of the whole of the experiments be brought together,
there is found, as between the number of forms with the dominant and
recessive characters, an average ratio of 2·98 to 1, or 3 to 1.
The dominant character can have here a _double signification_--viz.
that of a parental-character, or a hybrid-character[35]. In which
of the two significations it appears in each separate case can only
be determined by the following generation. As a parental character
it must pass over unchanged to the whole of the offspring; as a
hybrid-character, on the other hand, it must observe the same behaviour
as in the first generation.
[35] [This paragraph presents the view of the hybrid-character as
something incidental to the hybrid, and not “transmitted” to it--a
true and fundamental conception here expressed probably for the first
time.]