Oxford Democrat., 1920-06-08
Cross poliiuating.

Cross Pollinating.
| One might object to CROSS pollinatior
because when such Gross fertilization
takes place "scrub" is produced which
might be worse than either parent. II
such were the case It would be the height
Of folly to follow the teaching Of au
earlier letter In this series. It would be
far better for the Maine Agricultural
Experiment Station to be content with
the relatively small crop of apples now
being obtained from the 1900 Ben Davis
trees than to produce poorer apple than
the Ben Davis by -pollenization!
Neglecting the obvious sarcastic COM
ment that poorer apple than the Ben
Davis could not be produced, that oross-
pollination does not affect the quality OF
the apple is matter of common expert
ence. As pointed out In an earlier letter
in this series there are many varieties OF
apple trees that have never been known
70 produce single self-pollinsted fruit
But to test this out careful experiments
were made with varieties that can self
pollipste. Sek- -pollinsted and Cross pol
linated fruits were grown on the same
trees. These we're indistinguishable, the
one from the other In every particular,
so far as the fruit Is concerned. This
would have been expected from the fact
that the apple is like an enlarged branch
OF the mother tree. 1t does not receive
anything of genetic nature from the re
sulting union OF the pollen and the ovule.
1t Is the ovule alone that is affected by
this cross-pollinstion. The seeds from
self-pollinated and cross-pollinated fruit
will differ. But not the seed envelopes
Of which the flesh Of the pome is the
part that the apple grower is interested
in. A red apple will be just as red II
pollinated from green variety as II pol
linated with q red pollen variety. A
sweet apple will be just as sweet poli-
mated with wild crab as with sweet
variety. The resulting seeds from suob
crosses will be different, but the flesh
or marketable portion will remain un.
changed.
Although it may not have much prac
tca! Significance it is a matter of inter
est to learn, as far as one may, why most
apples are self-sterie and why some ap
Piles will not cross-fertilize with some
NdEl6tICb duu VIII VIII OtucEos
Sterility Of the apple is due to many
casual agents, which may be conveniently
grouped as external and as internal
Among the more commop external agents
that prevent fertilization Of the ovule are
diseases affecting the vitality of the trees
such as apple scab, and fire blight; In
sect infections; spray injury before, dur
ing or after Towering; and low tempera-
ture, cloudpess and colo continued rains
at Towering time. These factors which
are more or less under the control of the
grower are we'll recognized and the re.
medal agents and methods fairly we'll
understood by the practical grower.
The internal agents are not so easily
evident In the case of sterility. But in
general they have to do with the vigor
and kind of pollen and the ovule itself.
In the apple self-sterility to greater or
less amount Is apparently universal.
Successful crosses of self-sterile variety
with pollen from other varieties indicates
that the trouble is not with the ovule.
And on the other hand successful cross.
ing by using the pollen from such va
riety on another variety indicates that
the sterility Is not due to weak pollen.
Investigation has established the fact
that the problem Is one of interrelatiop
between the pistil and the pollen and the
pistil tube 1t has been found that iD
the self.sterile varieties when they are
sslf-fertilized that the pollen tube grows
more slowly than when the pollen Is de-
rived from other varieties. Thus in the
self-fertilized flower the rate of growth
- kha nh 10 oil hot
not traverse the length of the style and
fertilizs the ovule before the ovule with
ers and dies. With the CROSS, pollinated
flowers the pollen tube grows more rap
idly and easily reaches the ovule in time
for fertilization to take place. The ply.
sical basis of one form of this sterility
lies therefore in some of the factors
which hinders or prevents the growth of
the pollen tube in the style Of the same
variety. While this does not explain II
does locate the point Of attack to learn
the cause. And just what constitutes
this difference and how 1t may possibly
be overcome is still matter for investi-
cation.
The chief practical points brought ou:
In the three letters on apple sterility Of
which this Is the last are:
The apple grower should provide suit
able varieties for pollinators II large de-
pendable crops are to be had.
Random cross pollinston is not sud-
cient. 1t is necessary to learn the COM
patibility before any conclusion can be
drawn as to the variety to be selected as
pollinator.
The introduction of proper pollinators
increases the yield very materially.
The size, color and quality of the fruit
are not influenced by the kind Of pollen,
but depend upon the fixed character of
the mother parent.
The causes of self and cross. sterility
are to some extent external, and can be
largely controlled by proper orchard
management.
The chief internal cause of sterility is
the slowness of growth of the pollen
tube unless 1t has been stimulated by
compatible pollen. This cannot be con.
other than by taking steps necessary to
provide compatible pollen by the intro
duction Of suitable varieties.
CHAs. D. WOODS, Director.
The Maine Farmer on Ills Job.
Frank s. Adams of Bowdoinham, Chief
OF the Division of Markets, Maine De-
partment of Agriculture, has produced
some figures of interest to every person
in Maine, and especially every farmer in
Maine. He says:
"Did you realize that Maine farmers
are still doing businessP Why, just note
the following figures and judge whether
or not they have gone out Of or are con-
tinuing business at the old stand. These
figures are just summary of the Maine
farm products for the year 1919:
Commercial apples, 100000 bushels,
valne a. 600 OO0