[1] Introductory Remarks
In this paper, I will describe experiments in which I artificially fertilized plants. When I got the same results over and over again, I did further experiments. Some people spend their whole lives studying this branch of science.
To do this for your whole life requires
lots of courage to keep going when it gets tough or boring. To study that long is the only way to
discover the secrets of evolution.
This paper will now present the results
of an experiment. This experiment was
done on a certain group of plants, for eight years until I reached a
conclusion. The reader must decide
whether the results are correct or not.
To have a successful experiment, you
need to choose the right plants most suitable for the experiment.
The selection of the plants must be done
very carefully so as to not risk anything or get incorrect results. The plants must:
1. Have different traits.
2. The hybrids of the plants must,
during the flowering period, be protected from bugs that could pollinate them
and create incorrect results.
3. The hybrids and their offspring
should always be able to produce seeds that can be grown into more plants.
If bugs did pollinate the plants, it
would have a bad effect on the results.
If the plants could no longer produce seeds that could be grown into
more plants, the experiments would be very difficult and it could even end
them. To determine the relationship
between plants, the plants must be closely watched at all times.
34 different pea plants were gotten and
were put into a two-year trial. They
were allowed to fertilize themselves and 22 were selected that always produced
offspring that looked exactly like the parent plant.
Suppose you have two plants that are
different for one particular characteristic. The goal of this experiment was to
find out why, when the two plants are crossed, only one characteristic shows
up.
The characteristics that were selected for these experiments were:
1. The shape of
the ripe seeds: either round or wrinkled.
2. The color of the inside of the seed:
either pale yellow, bright yellow or orange colored.
3. The color of the seed coat: either white or grayish
brown.
4. The shape of the ripe pods: either puffed up or wrinkled
and squished.
5. The color of the unripe pods: either
green or yellow. *
6. The position of the flowers on the
stem: either distributed along the main stem or bunched at the top of the stem.
7. The length of the stem: either tall or short.
A plant with each characteristic was
crossed with a plant with the opposite characteristic, and the following
numbers of fertilizations were done:
1st experiment 60 fertilizations on 15 plants.
2nd experiment 58 fertilizations on 10 plants.
3rd experiment 35 fertilizations on 10 plants.
4th experiment 40 fertilizations on 10 plants.
5th experiment 23 fertilizations on 5 plants.
6th experiment 34 fertilizations on 10 plants.
7th experiment 37 fertilizations on 10 plants.
* One pea plant group had a brownish-red colored pod, which turned
violet or blue when it ripened.
The plants were grown in garden beds,
and a few in pots, and were kept upright using sticks, branches of trees, and
strings stretched between sticks. For each experiment a number of potted plants
were put in a greenhouse, to make sure the results were correct and to make
sure that bugs didn’t pollinate them.
In other experiments, it was found that
if you crossed, for example, a tall plant and a short plant, the hybrids
produced were not medium-sized, they were tall! Peas are exactly the same.
Only one characteristic is shown. The “shown” characteristic is called dominating and the “unshown”
characteristic is called recessive.
The characteristics that were dominant in these experiments were:
1. The round shape of
the seed.
2. The yellow color of
the inside of the seed.
3. The grayish-brown
color of the seed coat.
4. The puffed up shape
of the pod.
5. The green color of
the unripe pod.
6. The distribution of
the flowers along the main stem.
7. The tall stem.
In this experiment, the hybrids produced
in earlier experiments were allowed to self-fertilize. In this generation the dominant traits
reappeared, along with the recessive ones.
If there were four offspring plants, three would show a dominant
characteristic and one would show a recessive characteristic, making a 3:1
ratio.
The characteristics that were recessive were:
1.
The wrinkled seed.
2.
The green color of the inside of the seed.
3.
The white color of the seed coat.
4.
The wrinkled, squished shape of the pod.
5.
The yellow color of the unripe pod.
6.
The flowers bunched at the top of the stem.
7.
The short stem.
* Exp. 1: Shape of the seed: 253 plants and 7324 seeds
were gotten. There were 5474 round
seeds and 1850 wrinkled seeds. The
ratio was 2.96:1.
* Exp. 2: Color of the inside of the seed: 258 plants
and 8023 seeds = 6022 yellow and 2001 green.
The ratio was 3.01:1.
Experiment 1 Experiment
2
Shape of Seed Color of Inside of Seed
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
7 88
24 32 13
8 22
10 44 9
9 28 6 50 14
10 25
7 44 18
* Exp. 3: Color of the
seed coat: Among 929 plants, 705 had
grayish-brown seed coats and 224 had white seed coats, giving a ratio of
3.15:1.
* Exp. 4: Shape of the
pods: Of 1181 plants, 882 of them had
puffed up pods and 299 had wrinkled ones. The resulting ratio was 2.95:1.
* Exp. 5: Color of the
unripe pods: 428 had green pods and 152
had yellow ones, giving a ratio of 2.82:1.
* Exp. 6: Position of
flowers on the stem: Among 858 plants, 651 had flowers distributed evenly on
the stem and 207 had flowers only at the top, giving a ratio of 3.14:1.
* Exp. 7: Length of
stem: Out of 1064 plants, 787 had a
tall stem, and 277 had a short stem, giving a ratio of 2.84:1.
If the results of the whole experiment
were brought together, the average ratio was 2.98:1, or 3:1.
The plants from the previous experiment (the offspring produced when the hybrids self-fertilized) were allowed to self-fertilize. The plants that showed the recessive characteristic produced offspring that were also recessive. Of those plants that had the dominant character, two thirds of them actually were hybrids and had both the dominant and recessive character, and one third had only the dominant character, for a ratio of 2:1.
Those plants that had only the dominant character produced offspring that all showed the dominant characteristic. The remaining hybrid plants produced some offspring that showed the dominant characteristic and some that showed the recessive characteristic, in a ratio of 3 dominant to one recessive, just like when their hybrid parents were allowed to self-fertilize.
The separate experiments in which the
offspring that showed the dominant characteristic were allowed to
self-fertilize had these results:
* Exp. 1:
Among 565 plants that were raised from round seeds, 193 produced round
seeds only, and 372 produced some plants with round seeds and some plants with
wrinkled seeds, in a proportion of 3:1.
* Exp. 2:
Of 519 plants that were raised from seeds for which the inside of the
seed was yellow, 166 produced seeds that were yellow inside and 353 produced
some seeds whose insides were yellow and some seeds whose insides were green,
in a ratio of 3:1.
* Exp. 3: The offspring of 36 plants produced only gray-brown seed coats, while some of the offspring of 64 plants produced grayish-brown seed coats and some produced white seed coats..
* Exp. 4: The offspring of 29 plants produced only
puffed up pods while some of the offspring of 71 plants had puffed up pods and
some had wrinkled pods.
* Exp. 5: The offspring of 40 plants produced only
green pods, while some of the offspring of 60 plants produced green pods and some produced yellow ones.
* Exp. 6.: The offspring of 33 plants had only flowers
distributed on the stem, while some of the offspring of 67 had flowers
distributed on the stem and some had flowers bunched on the top.
*
Exp. 7: The offspring of 28
plants had only tall stems, while some of the offspring of 72 plants had tall
stems and some had short stems.
Summary: The offspring produced when hybrids self-fertilized can be
classified as either hybrids (possessing both the dominant and the recessive
character), dominant (possessing only the dominant character), or recessive
(possessing only the recessive character).
The ratio was 2 hybrids to one dominant to one recessive (2:1:1 ratio).
If A
refers to one of the two constant characters, for instance the dominant
character, and a refers to the
recessive characters, and Aa refers
to the hybrid form in which both characters are present, the expression
A + 2Aa + a
shows the proportion of offspring of the self-fertilizing hybrids.
Summary: Experiments were done in which plants were crossed that differed
in two or three characters. For
example, crosses were done among plants that differed in all three of the
following characters: seed coat form
(round or wrinkled), color of the inside of the seed (green or yellow) and seed
coat color (grayish-brown or white).
Summary: Each parent plant had two factors that were
able to pass on traits from parent to offspring, but that only one of those
factors was present in the egg cell or the pollen cell. So hybrid parent plants produced eggs or
pollen, and equal numbers of the egg or pollen cells had the dominant character
and the recessive character.
Separate experiments proved that this
was true of both pollen and egg cells.
It is purely a matter of chance, which of the two sorts of pollen will
become united with each separate egg cell.
So when crossing two hybrids (Aa X Aa),
the hybrids are able to produce, besides the two parental forms, offspring that
are like themselves. A/a and a/A both give the same union Aa, since it makes no
difference in the result of fertilization to which of the two characters the
pollen or egg cells belong. So A/A +
A/a + a/A + a/a = A + 2 Aa + a.
Summary: Other experiments were used to determine whether the laws
discovered for peas applied to the hybrids of other plants. Several experiments were done with different
species of beans.
With some crosses of beans, looking at
traits that determine the form of the plants, the ratios of the numbers in
which the different forms appeared in the separate generations were the same as
with peas. But in other crosses with
other species of beans, in which flower color was examined, the results were
confusing.
Summary: With peas it was shown by experiment that the hybrids form egg
and pollen cells of different kinds, and that this holds the key to the
variability of their offspring. So in
peas, it is beyond a doubt that when a new embryo is formed, a perfect union of
the elements of both reproductive cells must take place. How could we otherwise
explain that among the offspring of the hybrids, both original types reappear
in equal numbers and with all their peculiarities?
But even the truth of the law formulated
for peas must still be confirmed and some of the more important experiments
must be repeated.
It is important to compare the
observations made regarding peas with the results arrived at by the two
authorities in this branch of knowledge, Köreuter and Gärtner, in their
investigations. A description follows of experiments carried out by Kölreuter,
Gärtner, and others, including experiments made with respect to the
transformation of one species into another by artificial fertilization.