Shasta Daisies by Mr. Burbank's Porch
Mr. Burbank took what the farmers of New England
had always considered a troublesome weed — the daisy — and
transformed it into a flower of wondrous beauty. Every step in this
transformation is explained in detail in the opening chapter of
this volume. The direct color photograph print above, of
Mr. Burbank's door-yard, shows how the Shasta
daisy may be employed in lawn beautification.
LUTHER BURBANK
HIS METHODS AND DISCOVERIES AND
THEIR PRACTICAL APPLICATION
PREPARED FROM
HIS ORIGINAL FIELD NOTES
COVERING MORE THAN 100,000 EXPERIMENTS
MADE DURING FORTY YEARS DEVOTED
TO PLANT IMPROVEMENT
WITH THE ASSISTANCE OF
The Luther Burbank Society
AND ITS
ENTIRE MEMBERSHIP
UNDER THE EDITORIAL DIRECTION OF
John Whitson and Robert John
AND
Henry Smith Williams, M. D., LL. D.
VOLUME II
ILLUSTRATED WITH
105 DIRECT COLOR PHOTOGRAPH PRINTS PRODUCED BY A
NEW PROCESS DEVISED AND PERFECTED FOR
USE IN THESE VOLUMES
NEW YORK AND LONDON
LUTHER BURBANK PRESS
MCMXIV
Copyright, 1914, by
The Luther Burbank Society
Entered at Stationers' Hall, London
All rights reserved
Volume II — By Chapters
Foreword Page 3
I The Shasta Daisy
—How a Troublesome Weed »
Was Remade Into a Beautiful Flower I
II The White Blackberry
— How a Color Transformation
Was Brought About
HI The Scented Calla
— How Fragrance Was Instilled
in a Scentless Flower
IV The Stoneless Plum
— An Experiment in
Teaching a Plant Economy
VII The Burbank Cherry
— The Explanation of
a Double Improvement
VIII The Sugar Prune
— How a Tree Was Changed
to Fit the Weather
IX Some Interesting Failures
-The Petunia With
the Tobacco Habit — and Others
349357
39
V The Royal Walnut
— Speeding the Growth 197
of a Leisurely Tree -L O <
VI The Winter Rhubarb
— Making a Crop for -t s-(\
a High Priced Market J-O"
—The Petunia With 9 7 1
List of Direct Color Photograph Prints 305
FOREWORD TO VOLUME II
Having, now, a broad general understanding
of the work — of the underlying principles, of the
methods involved, and of the possibilities — let us
listen to Mr. Burbank as he tells us just how he
produced nine of his most striking transformations.
There are many Burbank productions which
may be rated as much more important to the
world than those treated in this volume; but
these have been selected because they reflect,
better than others, the various ways in which his
methods have been combined to produce final,
fixed results; thus serving to give the reader a
complete exposition of working detail in the
smallest possible space.
In this volume, then, we have Mr. Burbank's
own fascinating story, for the first time told, of
the exact steps which he took in producing a
number of widely different plant transformations;
together with many of his own observations on
life — plant, animal and human — from which we
gain a new insight into the relation between his
viewpoint and those of other workers in the same
and parallel lines.
THE EDITORS.
and
The Shasta Daisy
By comparing this new flower with its parents, shown
urther on, it will be seen that in size, shape, color, grace,
even leaf and stem, a new race has been created. More than ever
will this be appreciated when it is understood that
the flowers of the Shasta often attain
a diameter of eight inches.
THE SHASTA DAISY
How A TROUBLESOME WEED WAS RE-MADE
INTO A BEAUTIFUL FLOWER
WHITE is white," said one of my garden-
ers, "and all these daisies are white.
They look just the same color to me."
"Yes," I said, "white is white — there is no doubt
about that. But these daisies are not white — and
they do not look just alike to me. No one of them
is pure white, but there is one that is nearer white
than the rest, or else my eyes deceive me."
All the other gardeners agreed with the first
one, and it was some time before a visitor came
who was not of the same opinion. Person after
person was questioned, and each one declared
that all the daisies in the row seemed to be
pure white in color. No one could discriminate
between them.
But one day an artist from San Francisco
visited the garden, and when she was shown the
row of daisies and asked about their color, she
[VOLUME II — CHAPTER I]
LUTHER BURBANK
answered instantly that there was one much
whiter than all the rest; and to my satisfaction
she indicated the one that all along had seemed
quite different from the others to my eye. There
was no question, then, that this plant bore flowers
nearer to purity in whiteness than any others of
all the thousands of daisies in my garden.
Needless to say that particular plant was
selected for use in future experiments, for the
ideal I had in mind was a daisy that would be of
the purest imaginable white in color. How the
ideal was achieved — after fifteen years of effort —
will appear in due course.
The daisies in question, of which the plant
bearing the nearly white flowers was the best
example, had been produced by several years of
experimentation which had commenced with the
cultivation of the common roadside weed familiar
to every one in the East as the ox-eye daisy,
and known to the botanist as Chrysanthemum
leucanthemum. This plant, which grows in such
profusion throughout the East as to be considered
a pest by the farmer, was not to be found in
California until these experiments were begun.
I brought the plant chiefly as a souvenir of
boyhood days. But I soon conceived the idea
of bettering it, for it had certain qualities that
seemed to suggest undeveloped possibilities.
[8]
Original New England Ox-Eyes
The above direct color photograph print shows two New
England Ox-Eyes, actual size, such as Mr. Burbank brought
from his Massachusetts home when he came to California in 1875.
This transported flower or weed formed the basis of the
series of experiments which led to the
production of the Shasta Daisy.
LUTHER BURBANK
In its native haunts of New England, the
ox-eye, as everyone knows, is a very hardy plant
and a persistent bloomer. Its very abundance
has denied it general recognition, yet it is not
without its claims to beauty. But it did not greatly
improve or very notably change its appearance
during the first few seasons of its cultivation at
Santa Rosa; nor indeed until after I had given it
a new impetus by hybridizing it with an allied
species.
MATING THE OX-EYES
The plant with which the cross was made was
a much larger and more robust species of daisy
which I imported from Europe, where it is known
colloquially as the ox-eye daisy, although the
botanist gives it a distinct name, in recognition of
its dissimilar appearance, calling it Chrysanthe-
mum maximum. There is also a Continental
daisy, by some botanists considered as a distinct
species and named Chrysanthemum lacustre,
which is closely similar to the British species, and
of this seeds were secured from a German firm.
Both these plants have larger flowers than the
American daisy, but are inferior to it in grace of
form and abundance of bloom. The plants have
a coarse, weedy appearance, with numerous un-
sightly leaves upon their flower stalks, whereas
the stalk of the American daisy is usually leafless.
[10]
The Shasta Daisy and Two oj Its Parents
The upper flower is a form oj the Shasta Daisy
slightly different from that shown on page six, the curving rays of
which give a better realization of the kinship between the daisy and
the chrysanthemum. At the bottom are shown a Japanese
daisy at the left, and an European daisy at the rightt
proportionate size. The two small flowers
the bottom may truly be called direct
ancestors of the larger flower above.
isy a
both
LUTHER BURBANK
Notwithstanding the rather unsightly appear-
ance of the European ox-eyes, I determined to
hybridize them with the American ox-eye, in the
hope of producing a plant that would combine
the larger flowers of the European with the grace,
abundant flowers, and early blooming qualities
of the American daisy. The cross was first
made with the English daisy C. maximum, by
taking pollen from this flower to fertilize the
best specimens of the American daisy that I had
hitherto been able to produce.
When the seeds thus produced were sown next
season and the plants came to blooming time, it
was at once evident that there was marked
improvement. Some of the flowers appeared
earlier even than those of the American daisy;
they were very numerous, and were larger in size
than the flowers of either parent. But all the
flowers had a yellowish tinge, unnoticed by the
average observer, but visible to a sharp eye on
close inspection. And this tendency to dinginess
in color was not at all to my liking.
Further improvement was attempted by cross-
ing the hybrid plant with the German daisy just
referred to. A slight improvement was noticed,
but the changes were not very marked.
By selecting the best specimens of the hybrid,
which now had a triple parentage, I had secured,
[12]
THE SHASTA DAISY
in the course of five or six years, a daisy which
was very obviously superior to any one of the
original forms as to size and beauty of flower,
and fully the equal of any of them in ruggedness
and prolific blooming.
But the flowers were still disappointing in that
they lacked that quality of crystal whiteness
which was to be one of the chief charms of
my ideal daisy. So year by year I anxiously
inspected the rows of daisies in quest of a plant
bearing blooms whiter than the rest; and seeds
were selected only from the prize plants.
The daisy spreads constantly, and one root
stalk will, if carefully divided, presently supply a
garden. But of course each plant grown from the
same root stalk is precisely like the parent, and
while I thus secured a large bed of daisies
that combined approximate whiteness with all the
other good qualities I was seeking, yet the purest
of them all did not appear to my eye unqualifiedly
white.
And when my judgment was confirmed by the
decision of the artist, I determined to seek some
new method of further improvement that should
rid my daisies of their last trace of offending
pigment.
In casting about for a means to achieve this
end, I learned of an Asiatic daisy known to the
[13]
LUTHER BURBANK
botanist as Chrysanthemum nipponicam; and
presently I obtained the seed of this plant from
Japan.
AID FROM JAPAN
This Japanese daisy was in most respects
inferior to the original American ox-eye with
which these experiments had started. It is a
rather coarse plant, with objectionable leafy stalk,
and a flower so small and inconspicuous that it
would attract little attention and would scarcely
be regarded by any one as a desirable acquisition
for the garden. But the flower had one quality
that appealed to me — it was pure white.
Needless to say no time was lost, once my
Japanese plants were in bloom, in crossing the
best of my hybrid daisies with pollen from the
flowers of their Japanese cousin.
The first results were not reassuring. But in a
subsequent season, among innumerable seedlings
from this union, one was found at last with
flowers as beautifully white as those of the Jap-
anese, and larger than the largest of those that the
hybrid plants had hitherto produced. Moreover
the plant on which this flower grew revealed the
gracefulness of the American plant, and in due
course was shown to have the hardy vigor of all
the species.
From this remarkable plant, with its combined
[14]
The Shasta and a Selected European Ox-Eye
The direct color photograph print above gives a good
comparative idea of the difference in size between the
average Shasta daisy and the largest oj its European parents. The
European Ox-Eye, at the right above, is perhaps three times
as large as the average of its kind, and represents
an improvement in size and Jprm brought
purely through selection.
LUTHER BURBANK
heritage of four ancestral strains from three
continents, thousands of seedlings were raised
each year for five or six ensuing seasons, the
best individuals being selected and the others
destroyed according to my custom, until at last
the really wonderful flower that has since become
known to all the world as the Shasta Daisy was
produced.
So at last I had the pure white daisy of which
I had dreamed.
Moreover I had a flower that excelled my
utmost expectations as to size, grace and abundant
blooming qualities; a blossom from four to
seven inches in diameter, with a greatly increased
number of ray flowers of crystal whiteness, and
with flower stem tall and devoid of unsightly
leaves; a plant at once graceful enough to please
the eye and hardy enough to thrive in any soil;
a plant moreover of such thrifty growth that
it reached its blooming time in its first season,
although none of its ancestors bloomed until the
second season; and of such quality of prolificness
that it continues to bloom almost throughout the
year in California, and for a long season even in
the colder climates.
CONFLICTING TENDENCIES
The Shasta Daisy, sprung thus magically — yet
not without years of coaxing — from this curiously
'[16]
THE SHASTA DAISY
mixed ancestry, exceeded my utmost expectations
in its combination of desirable qualities. I can
hardly say, however, that the result achieved was
a surprise; for my experience with hundreds of
other species had led me to anticipate, at least in
a general way, the transformations that might be
effected through such a mingling of different
ancestral strains as had been brought about.
There was every reason to expect, while
hybridizing the American and European ox-eyes,
that a plant could ultimately be produced that
would combine in various degrees all the qualities
of each parent form. By selecting for preservation
only those that combined the desirable qualities,
and destroying those that revealed the undesirable
ones, a fixed, persistent hybrid race that very
obviously excelled either one of its parent forms
was produced.
Nor is there, perhaps, anything very mystifying
about this result, for the simpler facts of the
hereditary transmission of ancestral traits are now
matters of common knowledge and of every-day
observation.
No one is surprised, for example, to see a
child that resembles one parent as to stature, let
us say, and the other as to color of hair and eyes.
So a hybrid daisy combining in full measure
the best qualities of the European and the
[17]
LUTHER BURBANK
American ox-eyes, as did my first hybrid race,
perhaps does not seem an anomalous product,
although certainly not without interest, in view of
the fact that its parent stocks are regarded by
many botanists as constituting at least two distinct
species.
But the final cross, in which the Japanese plant
with its small flowers, inferior in everything except
color, was brought into the coalition, calls for
explanation. A general impression has long
prevailed that a hybrid race whether of animals
or of plants is likely to be more or less inter-
mediate between the parent races; so perhaps the
common expectation would have been that the
cross between the new hybrid race of daisies and
the obscure Japanese plant would result in a
hybrid with medium-sized flowers at best, and,
except possibly in the matter of whiteness of
blossom, an all round inferiority to the best plants
that I had developed.
And in reality, there appeared the beautiful
mammoth Shasta, superlative in all its qualities,
surpassing in every respect each and all of the
four parent stocks from which it sprang.
This apparently paradoxical result calls for
explanation. The explanation is found, so far as
we can explain the mysteries of life processes at
all, in the fact that by bringing together racial
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LUTHER BURBANK
strains differing so widely a result is produced
that may be described as a conflict of hereditary
tendencies. And out of this conflict conies a
tendency to variation.
The reasons for this are relatively simple.
Heredity, after all, may be described as the sum
of past environments. The traits and tendencies
that we transmit to our children are traits and
tendencies that have been built into the organisms
of our ancestors through their age-long contact
with varying environmental conditions.
The American ox-eye daisy, through long
generations of growth under the specific climatic
conditions of New England, had developed certain
traits that peculiarly adapted it to life in that
region.
Similarly the European daisy had developed a
different set of traits under the diverse conditions
of soil and climate of Europe.
And in the third place, the Japanese daisy had
developed yet more divergent traits under the
conditions of life in far away Japan, because these
conditions were not only more widely different
from the conditions of Europe and America than
these are from each other, but also because the
Japanese plant came of a race that had in all
probability separated from the original parent
stock of all the daisies at a time much more
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THE SHASTA DAISY
remote than the time at which the European and
American daisies were separated.
THE PLANT AS A CAMERA
To make the meaning of this quite clear, we
must recall that a given organism — say in this
case a given stock of daisies — is at all times
subject to the unceasing influence of the conditions
of life in the midst of which it exists. The whole
series of influences which we describe as the
environment is perpetually stamping its imprint
on the organism somewhat as the vibrations of
light stamp their influence on a photographic
plate.
Indeed, as I conceive it, the plant is in effect a
photographic plate which is constantly receiving
impressions from the environing world.
And the traits and tendencies of the plant that
are developed in response to these impinging
forces of the environment are further comparable
to the image of the photographic plate in that
they have a greater or less degree of permanency
according to the length of time during which they
were exposed to the image-forming conditions.
If you expose a photographic plate in a
moderately dim light, let us say, for the thou-
sandth part of a second, you secure only a very
thin and vague negative. But if without shifting
the scene or the focus of the camera, you repeat
[23]
LUTHER BURBANK
the exposure again and again, each time for only
the thousandth of a second, you will ultimately
pile up on the negative a succession of impres-
sions, each like all the rest, that result in the
production of a strong, sharp negative.
But if in making the successive exposures, you
were to shift the position of the camera each time,
changing the scene, you would build up a negative
covered with faint images that overlap in such a
way as to make a blurred and unmeaning picture.
And so it is with the plant. Each hour of its
life there come to it certain chemicals from the
soil, certain influences of heat and moisture
from the atmosphere, that are in effect vibrations
beating on its protoplasmic life-substance and
making infinitesimal but all-important changes in
its intimate structure. The amount of change
thus produced in a day or a year, or, under
natural conditions, perhaps in a century or in a
millennium, would be slight, for the lifetime of
races and plants is to be measured not in these
small units but in geological eras.
Nevertheless the influence of a relatively brief
period must make an infinitesimal change, com-
parable to the thousandth-second exposure of the
negative.
And when a plant remains century after
century in the same environment, receiving gen-
[24]
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LUTHER BURBANK
eration after generation the same influences from
the soil and atmosphere, the stamp of these
influences on its organic structure becomes more
and more fixed and the hereditary influence
through which these conditions are transmitted
to its descendants becomes more and more
notable and pronounced.
So it is that a plant that has lived for countless
generations in Japan has acquired a profound
heredity tending to transmit a particular set of
qualities; and when we hybridize that plant
with another plant that has similarly gained its
hereditary tendencies through age-long residence
in Europe, we bring together two conflicting
streams that must fight against each other and
strangely disturb the otherwise equable current
of hereditary transmission.
Long experience with the hybrids of other
species of plants had taught me this, and hence
it was that I expected to bring about a notable
upheaval in the hereditary traits of my daisies by
bringing the pollen of a Japanese plant to the
stigmas of my hybrid European and American
ox-eyes. That my expectations were realized, and
more than realized, is matter of record of which
the present Shasta Daisy gives tangible proof.
We shall see the same thing illustrated over
and over again in our subsequent studies.
[26]
THE SHASTA DAISY
In offering this explanation of the extraordi-
nary conflict of tendencies, with its resulting new
and strange combination of qualities that resulted
from the mixing of my various strains of daisies,
it will be clear that I am assuming that the
different ancestral races were all evolutionary
products that owed their special traits of stem
and leaf and flower to the joint influence of
heredity and environment.
I am assuming that there was a time in the
remote past when all daisies had a common
ancestral stock very different from any existing
race of daisies.
TOURING THE WORLD
The descendants of that ancestral stock spread
from the geographical seat of its origin — which
may perhaps have been Central Asia — in all
directions. In the course of uncounted centuries,
and along channels that are no longer traceable,
the daughter races ultimately made their way to
opposite sides of the world. Some now found
themselves in Europe, some in America, some in
Japan.
Thousands of years had elapsed since the long
migration began; yet so persistent is the power
of remote heredity that the daisies of Europe and
America and Japan even now show numerous
traits of resemblance and proof of their common
[27]
More Evidence oj Chrysanthemum Cousinship
The flowers shown above, selected from some of Mr.
Burbank's Shasta experiments, have more the appearance of
the chrysanthemum, almost, than oj the daisy. It will be noted that
the flower at the lower lejt gives evidence of doubleness to
such an extent that the center has begun to fill up.
Mr. Burbank has, in fact, produced some
daisies in which the center
is completely filled.
THE SHASTA DAISY
origin that lead the botanist to classify them in
the same genus. But, on the other hand, these
races show differences of detail as to stem and
leaf and flower and habit which entitle them to
rank as different species.
As the likenesses between the different daisies
are the tokens of their remote common origin and
evidences of the power of heredity, so their
specific differences betoken the influences of the
different environment in which they have lived
since they took divergent courses.
The Japanese daisy is different from the Ger-
man daisy because the sum total of environmental
influences to which it has been subjected in the
past few thousand years is different from the sum
total of influences to which the German daisy has
been subjected. Not merely differences due to
the soil and climate of Japan and Germany
today, but cumulative differences due to ancestral
environments all along the line of the migration
that led one branch of the race of daisies eastward
across Asia and the other branch westward across
Europe.
ARE ACQUIRED TRAITS TRANSMITTED?
But all this implies that the imprint of the
successive environments was in each case an
influence transmitted to the offspring; and this is
precisely what I mean to imply.
[29]
LUTHER BURBANK
To me it seems quite clear that the ohserved
divergencies between the European and the Jap-
anese daisy are to be explained precisely in this
way. I know of no other explanation that has any
semblance of plausibility.
It is my personal belief that every trait
acquired by any organism through the influence
of its environment becomes a part of the condition
of the organism that tends to reproduce itself
through inheritance.
In other words I entertain no doubt that all
acquired traits of every kind are transmissible as
more or less infinitesimal tendencies to the off-
spring of the organism.
But it would not do to dismiss the subject
without adverting to the fact that there are many
biologists who dispute the possibility of the trans-
mission of acquired traits. Indeed one of the most
ardent controversies of recent years has had to do
with that point; and doubtless many readers who
are not biologists have had their attention called
to this controversy and perhaps have received
assurance that traits acquired by an individual
organism are not transmitted.
I shall not here enter into any details of the
controversy, although doubtless we shall have
occasion to revert to it. But it is well to clarify the
subject in the mind of the reader here at the
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outset, by pointing out that this controversy, like
a good many others, is concerned with unessential
details, sometimes even with the mere juggling of
words, rather than with essentials.
As to the broad final analysis of the subject in
its remoter bearings, all biologists are agreed.
There is no student of the subject speaking with
any authority to-day, who doubts that all animal
and vegetable forms have been produced through
evolution, and it requires but the slightest consid-
eration of the subject to make it clear that Herbert
Spencer was right when he said that no one can
be an evolutionist who does not believe that new
traits somewhere and somehow acquired can be
transmitted.
Otherwise there could be no change whatever
in any organism from generation to generation or
from age to age: in a word there would be no
evolution.
The point in dispute, then, is not whether any
trait and modification of structure, due to the
influence of environment, is transmissible, but
only as to whether environmental influences that
affect the body only and not the germ plasm of
the individual are transmissible. But when we
reflect that the germ plasm is part and parcel of
the organism, it seems fairly clear that this is a
distinction without a real difference.
[32]
THE SHASTA DAISY
As Professor Coulter has recently said, it is
largely a matter of definition.
We shall have occasion to discuss this phase
of heredity more fully in another connection. In
the meantime, for our present purpose, it suffices
to recall that biologists of every school will admit
the force of the general statement that heredity
is the sum of past environments, and — to make the
specific application— that our Japanese daisies and
our German and American daisies are different
because long generations of their ancestors have
lived in different geographical territories and
therefore have been subject to diverse environing
conditions.
In a word, then, the Shasta Daisy which stands
today as virtually a new creation, so widely dif-
ferent from any other plant that no botanist would
hesitate to describe it as a new species, owes its
existence to the bringing together of conflicting
hereditary tendencies that epitomize the ancestral
experiences gained in widely separated geograph-
ical territories.
Without the aid of man, the plants that had
found final refuge in Europe and America and
Japan respectively, wrould never have been brought
in contact, and so the combination of traits that
built up the Shasta Daisy would never have been
produced.
[33]
LUTHER BURBANK
In that sense, then, artificial selection created
the Shasta Daisy, but the forces evoked were those
that nature provided, and the entire course of my
experiments might be likened to an abbreviated
transcript of the processes of natural selection
through which species everywhere have been
created, and are to-day still being created, in the
world at large.
NEW RACES OF SHASTAS
Once the divergent traits of these various
strains had been intermingled, the conflict set up
was sure to persist generation after generation.
Each individual hereditary trait, even though
suppressed in a single generation by the prepo-
tency of some opposing trait, strives for a hearing
and fends to reappear in some subsequent gen-
eration.
So the plant developer, by keenly scrutinizing
each seedling, will observe that no two plants of
his hybrid crop are absolutely identical; and by
selecting and cultivating one divergent strain or
another, he may bring to the surface and further
develop traits that had long been subordinated.
Seizing on these, T was enabled, in the course
of ensuing years, to develop various races of the
Shasta, some of which were so different that they
have been given individual names. The Alaska,
for example, has even larger and more numerous
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blossoms than the original Shasta, with longer
and stronger stems and more vigorous and hardy
growth. The Westralia has blossoms of even
greater size, and exceptionally long, strong and
graceful stems, and the California has a slightly
smaller flower but produced in great profusion;
and its blossoms instead of being snowy white like
those of the other races, are bright lemon yellow
on first opening.
Moreover the enhanced vitality due to cross-
breeding and the mingling of different ancestral
strains, was evidenced presently in a tendency to
the production not merely of larger blossoms, but
of blossoms having an increased number of ray
flowers.
The daisy is a composite flower, and the petal-
like leaves that give it chief beauty are not really
petals but are technically spoken of as rays. The
flowers proper, individually small and inconspic-
uous, are grouped at the center of the circling rays.
In all the original species the ray flowers consti-
tute a single row. But the hybrids began almost
from the first to show an increased number of
longer and wider ray flowers, some of which over-
lapped their neighbors.
By sowing seed from flowers showing this tend-
ency, I developed after a few generations a strain
of plants in which the blossoms were characterized
[36]
A Sport Among the Shastas
Among the thousands of aberrant forms which showed
themselves during the production of the Shasta daisy, none,
perhaps, was more strikingly singular than the sport or freak shown
above. In this, as will be seen, the rays, instead of being
flat and overlapping, are separate and tubular, flaring
out into graceful formations at the ends.
LUTHER BURBANK
by two rows of ray flowers instead of one. Con-
tinuing the selection, flowers were secured in
successive generations having still wider and
longer rays and increased numbers of rows, until
finally a handsome double-flowered variety was
produced.
Aberrant forms were also produced showing
long tubular ray flowers and others having the
rays fimbriated or divided at the tip.
And all these divergent and seemingly different
types of flowers, it will be understood, have the
same remote ancestry, and represent the bringing
to the surface — the segregation and re-combination
— of diverse sets of ancestral traits that had long
been submerged.
It is certain that no plant precisely like the
Shasta Daisy or any one of its varieties ever
existed until developed here in my gardens at
Santa Rosa. But the hereditary potentialities of
every trait of the new flower were of course
present in one or another strain of that quadruple
parentage, else they could never have made
appearance in the ranks of the hybrid progeny.
entertain no doubt as
to the transmissibility of
inherited or acquired traits.
THE WHITE BLACKBERRY
How A COLOR TRANSFORMATION
WAS BROUGHT ABOUT
TO SPEAK of white blackbirds or of white
blackberries is to employ an obvious con-
tradiction of terms. Yet we all know that
now and again a blackbird does appear that is
pure white. And visitors to my experiment
gardens during the past twenty years can testify
that the white blackberry is something more than
an occasional product — that it is, in short, a fully
established and highly productive variety of fruit.
I doubt, however, whether there is record of
anyone having ever seen a truly white blackberry
until this anomalous fruit was produced.
Nevertheless it should be explained at the out-
set that the berry with the aid of which I developed
the new fruit was called a white blackberry. It
was a berry found growing wild in New Jersey,
and introduced as a garden novelty, with no pre-
tense to value as a table fruit, by Mr. T. J. Lovett.
[VOLUME II — CHAPTER II]
LUTHER BURBANK
He called the berry "Crystal White," but this was
very obviously a misnomer as the fruit itself was
never white, but of a dull brownish yellow. It
had as little pretension to beauty as to size or
excellence of flavor, and was introduced simply
as a curiosity.
When a white blackbird appears in a flock, it
is usually a pure albino of milky whiteness. It
may be regarded as a pathological specimen, in
which, for some unknown reason, the pigment that
normally colors the feathers of birds is altogether
lacking.
It is not unlikely that the original so-called
white blackberry was also an albino of this
pathological type. But if so, hybridization had
produced a mongrel race before the plant was
discovered by man, or at least before any record
was made of its discovery; for, as just noted, the
berry introduced by Mr. Lovett could be termed
white only by courtesy.
Nevertheless the berry differed very markedly
from the normal blackberry, which, as everyone
knows, is of a glossy blackness when ripe. So
my interest in the anomalous fruit was at once
aroused, and I sent for some specimens for
experimental purposes soon after its introduc-
tion, believing that it might offer possibilities of
improvement.
[40]
The "Crystal White," So Called
Mr. Burbank learned that a wild blackberry of New
Jersey, pictured above, lighter in color than any other black-
berry, had been introduced as a garden novelty under the name
"Crystal White" Although lighter than any other blackberry,
it was of a muddy brown color, as can be seen from the
photograph; and the berries were small and oj
poor flavor. This wild berry, however, was
the first step in the production of
Mr. Burbank's perfected
white blackberry.
LUTHER BURBANK
Making use of the principles I have found suc-
cessful with other plants, my first thought was to
hybridize the brownish white berry with some
allied species in order to bring out the tendency
to variation and thus afford material for selective
breeding.
CREATING A REALLY WHITE BLACKBERRY
The first cross effected was with the Lawton
blackberry, using pollen from the Lawton berry.
The Lawton is known to be very prepotent; it is
of a very fixed race and will reproduce itself
from seed almost exactly, which is not true of
most cultivated fruits. Its seedlings often seem
uninfluenced when grown from seed pollenated
by other varieties.
It was to be expected, therefore, that the cross
between the Lawton and the "white" berry would
result in producing all black stock closely resem-
bling the Lawton; and such was indeed the result.
But the Lawton also imparts its good qualities
to hybrids when its pollen is used to fertilize the1
flowers of other varieties. As a general rule it is
my experience that it makes no difference which
way a cross is effected between two species of
plants. The pollen conveys the hereditary tend-
encies actively, and so-called reciprocal crosses
usually produce seedlings of the same character.
That is to say, it usually seems to make no
[42]
The Lawton Blackberry
A fine flavored, well fixed race oj blackberries is the
Lawton, shown above. If the pollen of the wild white berry
had been applied to the pistil of the Lawton berry little variation could
have been expected, the latter being so prepotent. But, by apply-
ing pollen from the Lawton berry to the flower of the so-called
"Crystal White," Mr. Burbank produced variations
which retained the lightness of color of the
wild parent and combined the size,
flavor and other good qualities
of the well fixed Lawton.
LUTHER BURBANK
practical difference whether you take pollen from
flower A to fertilize flower B, or pollen from flower
B to fertilize flower A.
This observation, which was first made by the
early hybridizers of plants more than a century
ago, — notably by Kolreuter and by Von Gaertner,—
is fully confirmed by my observations on many
hundreds of species. Nevertheless it occasionally
happens that the plant experimenter gains some
advantage by using one cross rather than the
other. In the present case it seemed that by using
the Lawton as the pollenizing flower, and growing
berries on the brownish white species, a race was
produced with a more pronounced tendency to
vary.
Still the plants that grew from seed thus pro-
duced bore only black berries in the first genera-
tion, just as when the cross was made the other
way. It thus appeared that the prepotency of
the Lawton manifested itself with full force and
certainty whether it was used as the staminate or
as the pistillate flower.
When the flowers of this first filial generation
were interbred, however, the seed thus produced
proved its mixed heritage by growing into some
very strange forms of vine. One of these was a
blackberry that bloomed and fruited all the year.
This individual bush, instead of dying down like
[44]
THE WHITE BLACKBERRY
others, kept growing at the top like a vine or tree,
and when it was two or three years old it was so
tall that a step-ladder was required to reach the
fruit. Its berries, however, were rather small, soft,
and jet black in color.
This plant, then, was an interesting anomaly,
but it gave no aid in the quest of a white black-
berry.
But there were other vines of this second filial
generation — grandchildren of the Lawton and the
original "Crystal White"— that showed a tendency
to vary in the color of their fruit, this being
in some cases yellowish white. Of course these
bushes were selected for further experiment. Some
were cross-fertilized and the seed preserved.
The vines that grew from this seed in the next
season gave early indications of possessing varied
qualities. It is often to be observed that a vine
which will ultimately produce berries of a light
color lacks pigment in its stem, and is greenish or
amber in color, whereas the stem of a vine that is
to produce black berries is dark brown or purple.
A few of the blackberry vines of the third genera-
tion showed this light color; and in due course,
when they came to the fruiting age, they put forth
heavy crops of clear white berries of such trans-
parency that the seeds, though unusually small,
could readily be seen through the translucent pulp.
[45]
Signs oj Success — Yellow-White Berries
From among many^ crosses between the Lawton and the
poor ""Crystal White," a berry very much improved in size
was secured, as shown above, and the form, texture and flavor were
brought up to the point, almost, of the good Lawton parent,
while the color, though still Jar Jrom white, was much
lighter than even that ot the wild ""Crystal White"
THE WHITE BLACKBERRY
These were doubtless the first truly white
blackberries of which there is any record. But
there were only four or five bushes bearing these
white berries in an entire generation comprising
several hundred individual bushes, all having pre-
cisely the same ancestry.
From among the four or five bushes, the one
showing a combination of the best qualities was
selected and multiplied, until its descendants
constituted a race of white blackberries that
breeds absolutely true as regards the white fruit
Now BREEDS TRUE FROM SEED
The descendants of this particular bush were
widely scattered and passed out of my control.
But subsequently from the same stock, I developed
other races, and finally perfected, merely by selec-
tion and interbreeding from this same stock, a
race of white blackberries that breeds true from
the seed, showing no tendency whatever to revert
to the black grand-parental type.
This is, in short, a fruit which if found in the
state of nature would unhesitatingly be pro-
nounced a distinct species. Its fruit is not only
snowy white in color, but large and luscious, com-
parable in the latter respect to the Lawton berry
which was one of its ancestors.
"Was there ever in nature a berry just like
this?" a visitor asked me.
[47]
LUTHER BURBANK
Probably not; but there was a small white
berry and a large luscious black one, and I have
brought the best qualities of each together in a
new combination.
THE ANOMALY EXPLAINED
Reviewing briefly the history just outlined, it
appears that the new white blackberry had for
grandparents a large and luscious jet black berry
known as the Lawton blackberry and a small
ill-flavored fruit of a yellowish brown color. The
descendant has inherited the size and lusciousness
of its black ancestor, and this seems not altogether
anomalous. But how shall we account for the fact
that it is pure white in color, whereas its alleged
white ancestor was not really white at all?
The attempt to answer that question brings us
face to face with some of the most curious facts
and theories of heredity. We are bound to
account for the white blackberry in accordance
with the laws of heredity, yet at first blush its
dazzling whiteness seems to bid defiance to these
laws, for we can show no recognized white
ancestor in explanation.
A partial solution is found if we assume, as we
are probably justified in doing, that the original
stock from which the so-called "Crystal White"
berry sprang was a pure albino. It has already
been suggested that such was probably the case.
[48]
THE WHITE BLACKBERRY
There is, indeed, no other very plausible expla-
nation available of the origin of the anomalous
berry. White is not a favorite color either among
animals or among vegetables. Except in Arctic
regions it is very rare indeed to find an unpig-
mented animal or bird, and white fruits are
almost equally unusual.
In the case of animals and birds, it is not diffi-
cult to explain the avoidance of white furs and
feathers. A white bird, for example, is obviously
very conspicuous, and thus is much more open to
the attacks of its enemies than a bird of some
color that blends with its surroundings. So we
find that there is no small bird of the Northern
Hemisphere, with the single exception of the snow-
bunting, which normally dresses wholly in white.
The exception in the case of the snow-bunting is
obviously explained by the habits of the bird itself.
And even this bird assumes a brownish coat in
the summer.
There are a few large water-fowl, notably the
pelican and certain herons that wear snowy white
plumage habitually throughout the year. But
these are birds of predacious habits that are little
subject to the attacks of enemies, and it has been
shown that the white color, or bluish white, tends
to make the birds inconspicuous from the view-
point of the fish that are their prey.
[49]
LUTHER BURBANK
So in the case of the tiny snow-bunting and of
pelicans and herons, the white color of the plum-
age is seen to be advantageous to its wearer and
hence is easily explained according to the prin-
ciple of natural selection. The same is true of the
white plumage assumed by those species of grouse
and ptarmigan that winter in Arctic or sub-arctic
regions; and contrariwise, the pigmented coats of
the vast majority of the birds and animals of
temperate zones are accounted for on the same
principle.
But just why the fruits of plants should almost
universally be pigmented seems at first not
quite so clear. It is ordinarily supposed to be
advantageous for a plant to have its fruit made
visible to the birds and animals, that the aid of
these creatures may be gained in disseminating
the seed. And it must be obvious that a
white blackberry would be as conspicuous in the
woodlands where this vine grows as are the jet
black berries of the ordinary type.
Why, then, you ask, has not natural selection
developed a race of white blackberries?
I am not sure that any one can give an
adequate answer. Perhaps it is desirable to have
the seeds of a plant protected from the rays of
the sun, particularly from those ultra-violet rays
which are known to have great power in producing
[50]
Some Lea/ Variations
Not only were the effects of the crosses evident in the
berries, but in the leaves as well, as can be seen from the
color photograph print above. In his almost endless selection from
the variations produced. Mr. Burbank bore in mind not only
the color and quality oj the berries, but the size.
shape and abundance of leaves, since, in the
final result, these organs oj digestion are
to play an important part.
LUTHER BURBANK
chemical changes. Recent studies of the short
waves of light beyond the violet end of the
spectrum show that they have strong germicidal
power.
It will be recalled that the celebrated Danish
physician Dr. Finsen developed a treatment of
local tubercular affections based on the principle
that ultra-violet light destroys the disease germs.
And most readers have heard of Dr. Woodward's
theory that very bright light is detrimental to all
living organisms.
Possibly too much sunlight might have a dele-
terious effect on the seeds of such a plant as the
blackberry. Indeed, the fact that the berry quickly
develops pigments under ordinary conditions, and
develops them much earlier than the stage at
which it is desirable to have the fruit eaten by
birds, suggests that this pigment is protective to
the fruit itself in addition to its function of
making the fruit attractive to the bird.
But be the explanation what it" may, the fact
remains that very few fruits in a state of nature
are white; and no one needs to be told that fruits
of the many tribes of blackberries, with the single
exception of the one under present discussion, are
of a color fully to justify the name they bear. Yet
the experiment in breeding just recorded proves
that, at least under the conditions of artificial
[52]
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I
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!?' «§ S § £. S S
LUTHER BURBANK
selection, a race of berries may be developed
which, though having the flavor and contour of the
blackberry, is as far as possible from black in
color.
The fact that this race of white berries was
developed in the third generation from parents
one of which is a jet black fruit and the other a
fruit of a brownish tint, seems at first glance to
give challenge to the laws of heredity.
ATAVISM AND UNIT CHARACTERS
Even though we assume that a remote ancestor
of our newly developed white blackberry was a
pure albino, the case still seems mysterious. Sim-
ilar cases of reversion to the type of a remote
ancestor have been observed from time to time
by all breeders of animals and by students of
human heredity, and it has been customary to
explain such cases of reversion, or at least to label
them with the word "atavism."
If this word be taken to imply that all traits
and tendencies of an ancestral strain are carried
forward from generation to generation by heredity,
even though unable to make themselves manifest
for many generations, and that then, through some
unexplained combination of tendencies, the sub-
merged trait is enabled to come to the surface and
make itself manifest, the explanation must be
admitted to have a certain measure of tangibility.
[54]
THE WHITE BLACKBERRY
Nevertheless there is a degree of vagueness
about the use of the word "tendencies" that robs
the explanation of complete satisfactoriness.
Meantime the human mind is always groping
after tangible explanations of observed phenom-
ena. It is always more satisfactory to be able to
visualize processes of nature. It was for this rea-
son that Darwin's theory that natural selection is
the most powerful moving factor in the evolution
of races gained such general recognition and still
remains as the most satisfactory of all hypotheses
of evolution.
And it is for the same reason that a tangible
explanation of the phenomena of atavism or the
reversion to ancestral types has gained a tremen-
dous vogue in recent years.
The explanation in question is associated with
the name of the Austrian monk Mendel, who made
some remarkable experiments in plant breeding
about half a century ago, and who died in 1884,
but whose work remained quite unknown until his
obscure publications were rediscovered by Pro-
fessor Hugo De Vries and two other contemporary
workers, and made known to the world about the
year 1900. Since then a very large part of the
attention of the biological world has been devoted
to the further examination of what has come to be
spoken of as Mendelian principles.
[55]
Color Variations in the Canes of the Blackberry
Not only is the leaf a guide to the kind of fruit which a
plant will produce, but in many cases the stem or cane gives a
reliable indication. With most berries it is the rule that the light stalk
will produce the lightest color berry — and the darker the stalk
the darker the berry. From the variations above it
will be seen that Mr. Burbank was able to
select for lightness of color even before
he used the leaves as an indi-
cation to size and form.
Some Stems oj the Blackberry's Cousin
The direct color photograph print above shows some
typical rose stems — varying in color, shape and thorniness.
The rose, and the blackberry, and the apple, and sixty-two other plants,
dissimilar in appearance, are all members of the same family*
and often give evidence of the possession of common
family traits. In his work with the rose, described
later* Mr. Burbank made use of similar
methods to those employed in *.he
production of the white
blackberry.
LUTHER BURBANK
And, as is usual in such cases, unwarranted
expectations have been aroused in some quarters
as to the real import and meaning of the new point
of view; also a good deal of misunderstanding as
to the application of the so-called Mendelian laws
of heredity to the work of the practical plant
developer.
In view of the latter fact it is well to bear in
mind that such experiments in plant breeding as
those through which I developed the white black-
berry and hundreds of others were made long
before anything was known of Mendel and his
experiments, and at a time when the conceptions
now associated with Mendelism were absolutely
unknown to any person in the world. It is well
to emphasize this fact for two reasons: first, as
showing that practical breeding, resulting in the
bringing to the surface of latent traits, — for
example, whiteness in the blackberry, — could be
carried to a sure and rapid culmination without
the remotest possibility of guidance from "Men-
delism"; secondly, because from this very fact
the interpretation of my experiments has fuller
significance in its bearing on the truth of the
Mendelian formulas than if the experiments had
been made with these formulas in mind.
This is true not alone of the creation of the
white blackberry, but of the similar development
[58]
THE WHITE BLACKBERRY
of the Shasta Daisy and of a host of other new
forms of plant life that will find record in succes-
sive chapters of the present work.
But while I would thus guard the reader
against the mistake, which some enthusiasts have
made, of assuming that the Mendelian formula
about which so much is heard nowadays must
revolutionize the methods and results of the plant
breeder, I would be foremost to admit that the
remarkable work of Mendel himself, together
with the work of his numerous disciples of the
past ten years, has supplied us at once with
several convenient new terms and with a tangible
explanation or interpretation of a good many facts
of plant and animal heredity that heretofore have
been but vaguely explicable, even though clearly
known and demonstrated as facts.
The case of the white blackberry with which
we are at the moment concerned, is a very good
illustration in point.
My experiments in the development of that
berry, might be interpreted in the older terminol-
ogy something like this: The big, luscious, black
Lawton blackberry proved prepotent when crossed
with the small brownish "Crystal White," and the
offspring were therefore all large luscious black
berries closely similar to the prepotent parent.
But the qualities of the other parent were latent in
[59]
The Stem Finally Selected
The direct color photograph print above shows the stem
of the final white blackberry. By comparing its color with the
color of other stems shown, it will be seen that the dark, purplish-brown
of the black Lawton has given way to the light greenish stem of the final
white blackberry. The color of the stem, it should be understood, is
only a guide to the color of the berry which is later to be produced. It
does not form the basis of an absolute, fixed law, for outcroppings oj
old heredity sometimes appear in the stem but not in the fruit. The selec-
tion by the stems, is, however, of sufficient certainty to warrant its use in
such experiments as the production oj the white blackberry. Where it
failed as a guide in three or Jour cases, it succeeded in
hundreds or thousands of cases.
THE WHITE BLACKBERRY
these offspring, and, — the tendency to variation
having been stimulated by the hybridizing of these
different forms, — the offspring of the second gen-
eration showed great diversity, and a tendency to
reversion to the traits of the more obscure or less
prepotent of the two grandparents.
In the still later generations, the conflict of
hereditary tendencies continuing, an even more
striking reversion, according to the principle of
atavism, took place in the case of a few of the
many progeny, bringing to light the pure white
berry as an inheritance from a remote and long
forgotten ancestor.
THE MENDELIAN EXPLANATION
Now this, as I say, would fairly explain the case
of the white blackberry in such terms as were uni-
versally employed at the time when this interesting
fruit was developed.
But the evolutionist of today, considering the
same facts, would be likely to offer an explanation
in Mendelian terms that would have the merit of
adding a certain measure of tangibility to the
mental picture of the actual processes involved
in the hereditary transmission of traits through
which the white blackberry was developed. And
there can be no question of the convenience of
these terms and of their value in aiding to conjure
up such a picture, provided it be not supposed that
[61]
LUTHER BURBANK
the presentation of such a formula is to clarify all
the mysteries of heredity and to do away with the
necessity in the future — as some misguided enthu-
siasts have assumed — of laborious and patient
experiments akin to those through which the tri-
umphs of the plant developer have been achieved
in the past.
In a word, the Mendelian formulas, if accepted
at their true valuation and for their real purpose,
may be regarded as placing new and valuable
tools in the hands of the plant experimenter, just
as did the formula of natural selection as put for-
ward by Darwin; but we must in one case as in the
other guard against imagining that the phrasing
of a formula may properly take the place of the
practical observation of matters of fact.
Bearing this caution in mind, let us note the
changed terminology in which the Mendelian of
today interprets the observed facts of the develop-
ment of the white blackberry. His explanation
would run something like this:
When the Lawton blackberry is crossed with
the whitish berry, all the offspring of the first filial
generation are black because blackness and white-
ness are a pair of "unit characters," both elements
or factors of which cannot be manifested in the
same individual; and blackness is the "dominant"
character of the two, whiteness being "recessive."
[62]
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LUTHER BURBANK
But the hereditary factors or "determiners"
that make for whiteness, though momentarily sub-
ordinated, are not eliminated, and half the germ
cells produced by the hybrid generation in which
blackness is dominant, will contain the factor of
whiteness, whereas the other half contain the
factor of blackness. And when in a successive
generation a germ cell containing the factor of
whiteness unites with the germ cell of another
plant similarly containing the factor of whiteness,
the offspring of that union will be white, their
organisms inheriting no factor of blackness
whatever.
It may chance, however, that for many succes-
sive generations a germ cell containing only the
factor of whiteness fails to mate with another
similar germ cell and so no white-fruited progeny
is produced. In such a case generation after gen-
eration the white factors continue to be produced
in the germ cells, but the union with a germ cell
containing the black factor obscures the result just
as in the case of the first cross, because the factor
of blackness continues to be dominant.
But, however long delayed, when a cell con-
taining the white factor or determiner does mate
with a similar cell, the offspring is white and — in
the older terminology — reversion or "atavism" is
manifested.
[64]
THE WHITE BLACKBERRY
A very simple and tangible illustration of the
phenomena in question is furnished by the experi-
ments in animal breeding made by Professor
William E. Castle of Harvard. These experiments
furnish a peculiarly appropriate illustration in the
present connection because it chances that the
animals experimented with are comparable to our
blackberries in that they are respectively black
and white in color.
The animals used in the experiment are guinea
pigs.
AN ILLUSTRATION FROM THE ANIMAL WORLD
Professor Castle shows that if a black guinea
pig of a pure strain is mated with a white guinea
pig of a pure strain, all the offspring of the first
generation will be black; and it is therefore said
that blackness is prepotent or dominant, and
whiteness recessive. But if two of these black off-
spring are interbred, it is an observed fact that
among their progeny three out of four individuals
will be black like their parents and one of their
grandparents, and the fourth one will be white
like the other grandparent.
The Mendelian explains that the factor of
whiteness was submerged, dominated by the
factor of blackness, in the second generation; but
that half the germ cells of these black individuals
contained the factor of whiteness, and that by the
[65]
White Blackberries on the Bush
The direct color photograph print above gives evidence that
Mr. Burbank selected his white blackberries not only Jor color*
taste, size, firmness and the season of bearing, but also for the Jorm,
hardiness and other good qualities of the bush that bears them.
In the final production of any new Jruit all oj these
qualities and many others must enter into consid-
eration— and a perfect balance or combi-
nation oj them is the triumph
oj final selection.
THE WHITE BLACKBERRY
mere law of chance the union of these germ cells
brought together about one time in four two of the
cells having the recessive white factor; such union
resulted in a white individual.
Meantime by the same law of chance the other
three matings out of the four brought together in
one case two black factors and in two cases a
mixture of black and white factors.
As black is dominant, these individuals having
the mixed factors would be individually black
(just as those of the first cross were black) ; but
their progeny in due course will repeat the
formula of their parent by producing one white
individual in four.
It should be explained that the Mendelian, in
expressing this formula, usually substitutes for
the word "factor," as here employed, the newly
devised word "allelomorph," although the less
repellent equivalent "determiner" is gaining in
popularity. He calls the body substance of an
animal or plant a "zygote," and he describes an
individual that contains factors of a single kind,
as regards any pair of unit characters (say only
for blackness in the case of our blackberries or
Professor Castle's guinea pigs) as a "homozygote" ;
contrariwise a body having both types of factors
(blackberries or guinea pigs of the second genera-
tion, for example) as a "heterozygote."
[67]
LUTHER BURBANK
But these big words, while it is convenient to
know their meaning, need not greatly concern us.
It suffices to recall the convenient terms "domi-
nant" and "recessive"; to recognize that a good
many antagonistic traits may be classed as unit
characters; and to welcome the conception of the
division of the factors or determiners of such a
pair of unit characters in the germ cell, as enab-
ling us to form a tangible picture of the modus
operandi through which the observed phenomena
of heredity may be brought about.
MIXED HERITAGE OF THE BLACKBERRIES
It remains to be said that the case of our black-
berries is a little more complex than the case of
the guinea pigs just referred to, because there is a
second pigment involved. The "Crystal White"
berry, it will be recalled, was not white but brown-
ish in color. There were thus transmissible two
pairs of unit characters involved as regards the
matter of color, namely (1) black versus white,
and (2) yellow or brown versus white.
The black factor or determiner dominated
absolutely in the first generation; but in the second
generation a certain number of germ cells were
paired in such a way as to eliminate the black but
retain the yellow factor.
It required a third mixture of the germ-cell
factors to produce a union in which neither black
[68]
THE WHITE BLACKBERRY
nor yellow factors appeared, the offspring of this
union being of course the pure white blackberry.
The presence of the yellow factor accounts
for the further fact, to which reference should
be made, that there were various intermediate
types of berries, neither black nor white, which
appeared in successive generations but which are
eliminated by selection as they did not fall in with
our plan of development of a white race.
The explanation just given makes it clear that,
once a union of germ-cell factors having only the
white element was effected, the black and the
yellow factors being entirely eliminated from that
particular individual, the germ cells arising from
that individual would necessarily contain only the
factor of whiteness; hence that all the progeny of
that individual would "breed true" and produce
white berries.
Such is indeed the observed fact with my devel-
oped strains of white blackberries. Grown from
the seeds, these breed far truer to their parentage
than is the case with most cultivated fruits. As
to certain other qualities they may vary, but all
are white.
The Mendelian explanation obviously cannot
add any force to this observed and long ago
recorded fact.
But it does serve to explain the observed fixity
[69]
LUTHER BURBANK
and permanency of the new and anomalous breed.
It enables us in a sense to understand the para-
doxical fact that a berry having a whole galaxy
of black ancestors may have no strain of black-
ness, no tendency to reversion to the black type, in
its composition.
But we must not put the cart before the horse
by supposing that the new explanation adds any-
thing to the force of the previously observed facts.
Hypotheses are for the interpretation of observed
phenomena, not phenomena for the interpretation
of hypotheses.
One other word in this connection. To would-
be plant experimenters who ask my opinion of
matters connected with the old versus the new
interpretations of heredity, I am accustomed to
say:
"Read Darwin first, and gain a full comprehen-
sion of the meaning of Natural Selection. Then
read the modern Mendelists in detail. But then-
go back again to Darwin."
Bear in mind Professor J. M. Coulter's com-
ment that "Mendelism has extended from its
simple original statement into a speculative
philosophy," and try for your own satisfaction to
separate the usable formulae from the intricate
vagaries of the new creed of heredity.
Let me cite a recent assertion of Professor
[70]
The White Blackberry Perjected
The success of Mr. Burbank's production may be judged
by the firm, luscious, pure white fruit as shown above. The
white blackberry is now a thoroughly fixed race coming true from the
seed— a fruit which, if found in the state of nature, would
unhesitatingly be pronounced a distinct species. It is
whiter than the whitest blackberry man ever saw
before and compares in size and luscious-
ness with its paternal ancestor*
the Lawton.
LUTHER BURBANK
William E. Castle, himself one of the foremost
experimenters along the lines of the newest
theory :
"As to how a new race is begotten we have not
got much beyond Darwin; indeed many of us have
not got so far."
The man who has got as far as Darwin in the
matter of understanding racial origins, — to say
nothing of getting beyond him — even in our day,
is no tyro in the study of heredity.
—Read Darwin first;
then read the modern
Mendelists; and then
— go back to Darwin.
THE SCENTED CALLA
How FRAGRANCE WAS INSTILLED
IN A SCENTLESS FLOWER
NOT long ago a young woman visitor who
had learned that the function of odor in
flowers is to attract bees and other insects
made a remark at once naive and wise.
"It seems wonderful," she said, "that bees
and other insects should have the same taste in
perfumes that we human beings have. The rose
and the apple blossom are sweet to them as
well as to us; whereas one might expect that
they would care for something quite different,
especially when we remember that cultivated
people generally like more delicate perfumes than
those that please uncultivated people."
This remark, as I said, was at once wise and
nai've.
It was wise because it showed a tendency to
seek causes for things in nature instead of taking
them for granted as most people are prone to do.
[VOLUME II— CHAPTER III]
LUTHER BURBANK
It was nai've because it quite overlooked the
true significance of the function of odors in
nature.
A moment's further reflection would have
shown the young woman that it is not at all a
question of the bee liking the things that man
likes, but a question of man having learned to
like the things that the bee likes.
The scent of the flower was not put forth to
please or displease man, but to please and attract
the insect.
And man learned to like the odors that were
constantly presented to him largely because they
were constantly presented; just as you may learn
to like a food — say, for example, olives — by
repeatedly tasting it, though at first you do not
care for it.
The exception, of course, is the odor that
is associated with unhygienic things, such as
decaying vegetable and animal matter. These
are attractive to the insects that feed on them
because the substances that produce the odors are
to these insects wholesome. But they do not
attract the bee because they contain nothing on
which that insect can feed; and they do not
attract us because for us the substances that
produce them are pernicious.
But doubtless the carrion beetle finds the odor
[74]
THE SCENTED CALLA
of decayed meat a much more attractive aroma
than the odor of orange blossoms.
And, to make direct application to the case in
hand, unquestionably the flies and other insects
that are useful to the calla in pollenizing its
flowers would be quite unattracted by the sweet
and pervasive odor that is given out by the new
race of scented callas which I am about to
describe.
How THE CALLA Is FERTILIZED
It was on smelling the perfume of my scented
calla that the visitor made the remark I have
quoted. And she followed it with this question:
"If the odor of plants is of use to them in
attracting bees, why do not all the callas have a
perfume like this new one you have developed?"
And here again a moment's reflection would
perhaps have supplied the answer. The calla
does not need to attract the bee, therefore the
production of the chemical substances that give
out a sweet perfume would have been a waste of
energy for this flower. Perhaps there may have
been a time in the past when the calla, like so
many other flowers, depended on bees for cross-
fertilization, and lured them with its scent; but
nowadays the process of cross-fertilization in this
plant is effected in a quite different fashion.
If you closely examine the calla you will
[75]
LUTHER BURBANK
observe that what you would casually speak of
as a single blossom is in reality a case or shield-
in point of fact a modified leaf — twisted into a
sort of cornucopia and adjusted about a central
stalk or "spadix" on which many minute and
inconspicuous blossoms are clustered.
The object of this arrangement is doubtless in
part to give protection to the flowers, but largely
to supply a conspicuous signal to attract night-
roving insects, in particular various species of
small gnats and flies.
In point of fact the white canopy of the calla
affords a very convenient place of refuge for
numerous small insects.
Tests have shown that the air inside the calla
"blossom," particularly toward its base, where
the insects congregate, is perceptibly warmer than
the outside air.
It has been proved by recent experiments
that the chemical processes associated with plant
growth generate heat. Germinating seeds, for
example, give out a measurable quantity of heat.
So it is not strange, perhaps, that the partially
confined air at the base of the tubular calla
flower-case is at all times a little warmer than
the surrounding atmosphere.
In any event the insects find this a snug corner,
the attractiveness of which is further enhanced by
[76]
The Spadix of a Calla Lily
From this direct color photograph it will be seen
that the central stalk within the lily, called the spadix, is
in fact a composite flower itself, on which many minute and incon-
spicuous blossoms are clustered. These blossoms
may be clearly seen on the print above.
LUTHER BURBANK
the presence of a certain amount of edible pollen.
In short, for such insect tribes as like the particular
fare which the calla offers, its beautiful white
tube constitutes a highly attractive lodging-place
and lunchroom.
Meantime, while the insects are lodging at the
base of the stalk on which the true flowers grow,
these flowers shed their pollen and let it settle on
the backs of the visitors.
And when, in due course, the insects resume
their voyaging, they carry the pollen with them
and in time transport it to other calla blossoms;
for when they enter the new flower they are
likely to find the stalk at its center a convenient
alighting place, and crawling down this are sure
to leave some of the pollen in contact with
receptive pistils.
That the pistils shall be those of a different
plant from the one that supplied the pollen is
ensured by Nature's familiar device of having the
stamens and pistils of the same flower ripen at
different times.
A GIFT OF NATURE
All this sufficiently explains the utility of the
large white modified leaf or spathe which we
commonly speak of as the calla's flower, and also
the normal habit of this flower in producing only
the musty odor which is rather disagreeable to us,
[78]
THE SCENTED CALLA
but which is obviously attractive to the particular
insects which the calla needs as coadjutors.
But it does not explain how it chanced that
among a large quantity of seedlings of a tribe
of calla known as the "little gem," I one day
found a single specimen that not only lacked the
disagreeable smell of the others, but had a
mild yet unmistakable aroma that was distinctly
pleasing.
Explanations aside, such a specimen did appear
among my callas, and it was by raising seedlings
from this anomalous specimen and carefully
selecting the best specimens for successive gener-
ations that I developed the perfumed calla.
The first plants that grew in the first generation
from seeds of my first scented calla showed
no improvement over their parent in point of
fragrance. But in the second generation, as so
often happens, there was a marked tendency to
variation, and from among the numerous seedlings
of this generation I was able to select one that had
a fully developed and really delightful perfume.
By propagating this specimen as usual, by
division, scented callas precisely like the mother
plant were soon developed in quantity.
Other races showing the quality of scent-
production in varying measure were produced
from the seed, but no one of the seedling varieties
[79]
LUTHER BURBANK
ever equalled the selected plant, and the finest
fragrant callas in existence to-day are all the
descendants, through the process of division, of
the original second generation seedling.
This new race of callas was named the
"Fragrance."
Fortunately it chanced to combine with the
habit of perfume production the habit of abundant
and constant blooming. Indeed, in this regard
it probably excels all other varieties of calla.
THE NEW CALLA A "SPORT"
It thus appears that the perfumed calla was
developed through selection and in the short
period of two generations, from a perfumed
individual that appeared "spontaneously" among
some thousands of odorless seedlings.
Using a term that is peculiarly popular in
recent years, we might say that so marked a
variation from the normal or usual form of calla
constituted a "mutation."
In the size and color and general appearance
of its flower, as well as of its entire structure,
the new calla precisely resembled its fellows. Yet
we are surely justified in speaking of so very
marked an anomaly as the production of a strong
perfume as constituting an important departure
from the normal.
No one knows precisely what the chemical
[80]
A Freak Calla
ThisCalla Lily, found on Mr. Burbank's grounds, gives
a clear idea oj the relation of the spathe to spadix. It will
be seen that while the spadix bears the blossoms, the spathe is, in point
of fact, a modified leaf twisted into a sort of cornucopia around
it. Through some lack of balance in the heredity of
the plant shown above, the spathe took back to
the days, evidently, when this trans-
formation was in the making.
LUTHER BURBANK
changes are that produce the perfume of a flower,
or through precisely what transmutation of forces
one flower is made to produce an odor quite
different from the odor of other flowers.
But for that matter no one knows just what are
the conditions that induce the stimulus that we
interpret as an odor of any kind. The sense of
smell seems the most mysterious of our senses.
But whatever these inherent conditions may be,
they constitute changes in the intimate structure
of the plant itself that must be admitted to be
important in character, inasmuch as they have to
do with the well-being of the plant, and may even
determine — through their appeal or lack of appeal
to insects — the perpetuation or the elimination of
a species.
In the case of my scented calla it was perfume
alone that differentiated a particular individual
from thousands of other individuals growing in
the same plot.
On this basis alone I selected out this particular
flower, put it in a plot by itself, gave it every
encouragement, and determined that its progeny
should live and perpetuate the particular strain it
represented; whereas but for this single feature
of variation, that individual plant would in all
probability have been destroyed along with
hundreds of others.
[82]
THE SCENTED CALLA
The development of the scented calla, then,
through artificial selection based on the recog-
nition of the value of fragrance as an addition
to the attractiveness of this flower, represents
in a small way and in epitome the history of
the development of numberless races in nature
through the operation of natural selection.
In this particular case, natural selection prob-
ably would not have resulted in the production
of a race of scented callas, because, as already
pointed out, fragrance of this character has no
value for this particular flower. It might even
chance that the fragrance which to our senses
is exquisite would prove unattractive or even
repellent to the flies that normally frequent the
spathe of the calla and aid it in perpetuating its
species.
In that case natural selection would certainly
ensure the early destruction of the race of scented
callas. It may well have been through such
discriminative selection on the part of insects that
the calla lost its scent in the past ages. For of
course natural selection can operate quite as
effectively in weeding out organisms that have
undesirable traits as in perpetuating organisms
that show favorable variations.
One process is necessarily complementary to
the other; they are two sides of the same shield.
[83]
LUTHER BURBANK
In another connection we shall have occasion
to deal more at length with the processes of
natural selection; and we shall see numberless
examples before we are through of the way in
which artificial selection is instrumental in
developing new races of plants.
FOUNDATIONS OF NATURAL SELECTION
But for the moment I will consider a little
more at length the question of the origin of the
variation which resulted in giving this particular
calla a perfume that was not normal to its race.
In so doing, we shall gain a clue to the genesis of
other types of variation or mutation through which
various and sundry new races of cultivated plants
have originated, and through which also, we have
every reason to believe, numberless species of
animals and plants in a state of nature have been
evolved.
The presentation of this subject puts us in
touch with one of the newest and doubtless one
of the most important aspects of the problem of
evolution.
Since Darwin we have fully understood that
all evolution of organic forms must have its origin
in variations. No two individuals even of the same
species are precisely alike, and it is not at all
unusual to find individuals of a species showing
very considerable differences, even as regards the
[84]
Another Freak Calla
This oddity was observed on one of Mr. Burbank's yellow
Calla plants. It will be noted that the true leaf shows a
tendency to turn yellow, while the spathe has the green markings of
the leaf on its back. This is but one of innumerable freaks or
sports such as are encountered in large quantity
production of plants; and it is from these odditiest
oftent that new ideas of old and useful
heredity within the plant are made
evident to the plant improver.
LUTHER BURBANK
essentials of size and form and function. Indeed,
a certain range of such variations is considered
to be absolutely normal.
One would never state, for example, that any
particular bird has a wing or beak or tail of
precisely a given length; instead of this the
ornithologist records the average or mean length,
or the limits of variation shown by different
specimens.
And it is universally recognized, since Darwin
gave us the clue, that the building up of new
species must be brought about through the selec-
tion of favorable variations. A bird with an extra
long wing, for example, might be able to fly a
little faster and secure its insect prey with greater
facility than its fellows; and this slight advantage
might be instrumental in saving the life of such a
bird, and thus enable it to transmit its peculiarity
to offspring that would constitute a long-winged,
swift-flying race.
Take the following incident as a tangible
illustration :
In the summer of 1904 it chanced that there
was a severe drought in New England and there
were entire regions in which the insects upon
which the common house martin feeds failed to
be hatched at the usual time. The result was
that there was dearth of food for the martins, and
[86]
THE SCENTED CALLA
a very large proportion of these birds died of
starvation.
In some cases forty or fifty birds would be
found starved to death in a single bird-house.
There are entire regions in New England
to-day where the martin is a rare or unknown
bird, although prior to 1904 it was abundant.
Now we may reasonably assume that any
individual martins that escaped were those that
had either greater powers of flight or a stronger
inherent tendency to make wide flights in search
of food than their fellows. The few individuals
thus saved furnish us a concrete example of the
survival of the fittest through natural selection.
And this illustration is cited at length because it
makes tangible the fact, to which I shall have
occasion to revert time and again, that the
processes of nature through which species have
been developed in the past are still in operation
everywhere about us.
Many people are disposed to think of natural
selection as a principle referring to past times
and to the development of organisms long since
perfected.
In point of fact past times are like present
times in the operation of their laws. The
re-actions between organism and environment are
now what they always were. No race is perfected,
[87]
LUTHER BURBANK
no organism freed from the struggle for existence;
although, of course, under the conditions of
civilization the operation of "natural selection"
may be modified through man's influence, and the
conditions of life for a given organism radically
changed by artificial selection.
EVOLUTION THROUGH MUTATION
But let us not forget our theme. With the
case of the scented calla to furnish our text, I
was about to speak of those variations from the
normal on the part of any given organism which
lie outside the ordinary range of variation and
;which therefore constitute so definite and pro-
nounced a departure that they have long been
spoken of as "sports."
To these the present day evolutionist, following
Professor Hugo de Vries, gives the name of
"mutations."
It has already been said that the appearance of
a scented calla constitutes such a change. But of
course the anomalies that are usually listed as
mutations are as a rule of an even more noticeable
character. A classical illustration was given by
Darwin himself in the case of the Ancon ram,
which was born with legs only half the normal
length, and from the progeny of which was
developed a short-legged race of sheep.
But the word mutation had not come into
[88]
Mr. Burbank's Original Yellow Calla
The plant from which this flower was developed is of
African origin. It is a not distant relative of the familiar White
Calla, belonging to the Genus Richardia. These plants, although
universally called Callas by the florist, are not so named by the
botanist, the true Calla being a quite different flower of no
great horticultural importance. The Yellow Calla, known
also as the Pride of the Congo, was originally of
a greenish yellow color, but has been made
to take on the rich hues above
shown by selective breeding.
LUTHER BURBANK
vogue in Darwin's time, and the idea of evolution
through such marked departures from the normal
was subordinated, in Darwin's interpretation of
the origin of species, or at least in that of his
immediate followers, to the idea of advance
through the preservation of slight variations.
So when, just at the close of the nineteenth
century, Professor Hugo de Vries came forward
with his "mutation theory," it had all the force of
a new doctrine, and was even thought by some
enthusiasts — though not by its originator — to be
in conflict with the chief Darwinian doctrines.
The observations that led Professor de Vries
to the development of this theory were made on a
familiar American plant that had found its way
to Europe and was growing in profusion by the
roadside near Amsterdam. The plant is known
as the evening primrose.
Professor de Vries noted a hitherto unde-
scribed variety of this plant in a field near
Amsterdam. He took specimens of the plant to
his famous experimental gardens and carefully
watched the development of successive genera-
tions of seedlings.
To his astonishment he produced in the course
of a few generations more than a dozen divergent
types of evening primrose, all descended from the
original plant, each of which bred true to the new
[90]
THE SCENTED CALLA
form suddenly assumed. Professor de Vries spoke
of these sudden and wide variations from type on
the part of his evening primrose as constituting
"mutations."
He conceived the idea that similar mutations
or sudden wide variations had probably consti-
tuted the material on which natural selection
had worked in the past. Such mutations being
observed to occur in the case of the evening
primrose, it is not unnatural to argue that
similar mutations must occur in the case of other
organisms; and it requires no argument to show
that such wide variations offer better material for
the operation of the laws of natural selection than
could be offered by the minute and inconspicuous
variations that had hitherto been supposed to
constitute the basis of evolutionary changes.
There were many reasons why the mutation
theory appealed to contemporary biologists, thus
accounting for its very cordial reception.
For example, there are numberless instances
in nature where the development of a useful
organ is exceedingly hard to explain on the basis
of natural selection, because the organ in its
incipient stages could have no utility. Similarly
a modification in the location of an organ — say
the shift in the flatfish's eye until both eyes are on
one side — is difficult to explain as a process taking
[91]
LUTHER BURBANK
place by infinitesimal stages, on the basis of
natural selection.
A slight shift in position of the eye of the flatfish
would have no utility whatever. It is only when
the shift has become sufficient to bring the eye on
the upper side of the fish that the creature would
have any advantage over other flat fish whose eye
is on the under side.
If we imagine a mutation in which a fish
appears with an eye distorted in location suffi-
ciently to be usable while its owner lies flat on
its side in the mud, we can readily understand
how such a mutation might be favorable to the
individual and thus might furnish material for
the development through natural selection of a
race of flatfish having both eyes on one side.
We have every reason to believe that the
races of flatfish now existing have recently —
in a geological sense — developed their observed
condition of having the eyes thus located; indeed
proof of this that amounts to demonstration is
furnished by the fact that the young flatfish even
to this day is born with its eyes located like those
of other fishes, the migration of the eye, so to
speak, taking place as the individual develops
the racial habit of lying on its side.
But as I said, it is unquestionably difficult to
conceive How tKe useful distortion came about
[92]
|8 ?1 ri^£!,~
i&rrr*
•«>
•SH
I
LUTHER BURBANK
unless it began suddenly as a "sport" or mutation.
This is one instance among many.
And so Professor de Vries' observation, which
proved that mutations do sometimes seemingly
occur "spontaneously" in nature was seized on as
affording a solution of one of the puzzles of
evolution, and the mutation theory was pretty
generally regarded as a valuable supplement to
the Darwinian theory of evolution.
It should be clearly understood, however, that
neither Professor de Vries himself nor anyone
else speaking with authority, has thought of the
mutation theory as in any sense contradicting the
Darwinian theory of natural selection. On the
contrary, it is to be regarded as supplementing
and supporting that theory. .If creatures are
subject to large variations in a single generation,
such variations afford peculiarly good material
for the operation of natural selection. Moreover,
evolution by mutation would presumably be
much more rapid than evolution that depended
for its' leverage upon minute variations.
WHAT CAUSES MUTATION?
Incidentally the idea of relatively rapid
evolution, thus given plausibility, answered the
objection of certain geologists who had questioned
whether the earth had been habitable long
enough to permit the evolution of the existing
[94]
THE SCENTED CALLA
forms of life through the cumulative effect of
slight variations.
The mutation theory is thus in many ways
acceptable. But to give the theory finality it is
obviously necessary to proceed one step farther
and ask this question: What causes mutation?
And it is equally obvious that the question must
be hard to answer.
Professor de Vries, to be sure, made the
assumption that the changes in his evening prim-
rose were probably due to altered conditions of
nutrition incident to the growth of the plant in a
new soil. He further developed a thesis that
probably all species are subject to mutation
periods, which recur at more or less regular
periods of their, life history, and which thus
ensure a degree of variation that will make racial
evolution possible.
The authority of de Vries sufficed to give wide
vogue to his theory; yet it must be admitted that
the explanation offered lacks tangibility and at
best amounts to little more than begging the
question.
To say that altered nutrition produces varia-
tion in a plant is in effect to state the fundamental
truth that all plants are more or less responsive
to their environment.
But there is nothing specific in the case
[95]
LUTHER BURBANK
of the primrose that explains in any precise
way the relation of the change to the particular
differences, let us say, between the soil of the
original home of the primrose and the soil of
Holland. Moreover in numberless other instances
plants have been transplanted from one region to
another without showing any such pronounced
tendency to develop new races.
It was recognition of the difficulties thus
presented, undoubtedly, that led Professor de
Vries to devise the rather visionary hypothesis of
periods of mutation with which his theory was
cumbered.
But it is a well recognized law of logic
that one should never seek remote and obscure
explanations of observed phenomena unless all
explanations of a more tangible character have
been proved untenable. And it has seemed to
me from the outset that in the case of the evening
primrose a very much more plausible explanation
is at hand than the one devised by the originator
of the mutation theory.
In a word, the varied tribes of evening primrose
which Professor de Vries developed in his gardens
at Amsterdam were overwhelmingly suggestive of
various and sundry new forms of hybrid plants
that I myself have developed year after year in
my experimental gardens at Santa Rosa.
[96]
THE SCENTED CALLA
The primus blackberry, the phenomenal berry,
and the sunberry, are, if you wish so to consider
them, instances of pronounced mutation, inas-
much as they are fixed forms of plants that vary
widely from the parent forms.
In a single row I can show walnut trees six
inches high that are of the same age with others
six feet in height, both grown from seeds of
the same tree. The Shasta daisy and the white
blackberry are mutants in the same sense. And
as the reader will discover in due course, the list
of such anomalies might be extended to tiresome
lengths.
In a word, it is perhaps not too much to say
that my entire work has consisted in dealing with
mutations in plant life. My chief work might be
held, and I believe justly held, to be an exposition
of the truth of the theory of mutation insofar as
it applies to the explanation of the origin of
species.
Over and over again, hundreds of times in the
aggregate, I have selected mutants among my
plants, and have developed from them new fixed
races. But in the vast majority of cases I knew
precisely how and why these mutants originated.
They were hybrids; and they were mutants
because they were hybrids.
And so from the outset I have believed that
[97]
LUTHER BURBANK
Professor de Vries' celebrated evening primroses
had the same origin. It is true that the parent
form was not known to be hybridized, and that
there was no known form of evening primrose
at hand through which hybridization could have
taken place.
But the precise origin of the original plants
found near Amsterdam is entirely unknown; and
the curious conformity of their offspring, under
Professor de Vries' observation, to the habitual
variation of hybrid races in the third and subse-
quent generations is so pronounced that it cannot
well escape the observation of anyone who has
had large experience with such races.
This fact was at first overlooked by most
biologists, largely because they lacked such
experience. But now there is a growing tendency
to take this view of the case.
Attempts have even been made in very recent
years to produce a similar series of mutational
forms of evening primrose by direct hybridization
of existing forms. And while the results have not
been absolutely definitive, they are unquestionably
suggestive; and there is without doubt a growing
appreciation of the fact that plants may be made
to take on the notable changes which we described
as mutations by the hybridizing of allied races;
and that this explanation of the origin of mutation
[98]
The Scented Calla
This color print shows Mr. Burbank's Jamous
scented Calla. It will be seen that the flower retains the physical
characteristics oj the ordinary Calla from which it was developed. The
scented variety was developed by selective breeding, the original
scented specimen being a "sport" that appeared among
the almost numberless specimens in Mr.
Burbank's garden. By similar selective
breeding Mr. Burbank has developed
and improved the odors of
many other flowers.
LUTHER BURBANK
has full validity, whether or not it be accepted as
the sole explanation.
We shall see the truth of this contention
illustrated in scores of cases in the course of these
studies.
THE FINAL INTERPRETATION
Meantime for the purposes of present illus-
tration it is necessary to revert to the case of our
scented calla.
After what has just been said it will be obvious
that I would explain this mutation as a reversion
due to cross-fertilization.
In other words, some remote ancestors of the
calla may have been scented, and a chance
mingling of ancestral germ plasms in the course
of the production of thousands of seedlings of
the calla, may have led to such a union of sub-
merged hereditary factors as enabled this latent
propensity to make itself manifest.
According to this view, the case is comparable
to that illustrated by an experiment in which
Professors Bateson and Punnett hybridized two
white-flowered peas of different strains and
produced offspring bearing flowers colored blue
and pink and purple.
The white parent forms were so nearly
identical as to be entirely indistinguishable
except that a magnifying-glass showed the pollen
[100]
THE SCENTED CALLA
grains of one form to be round and the pollen
grains of the other form to be oval. This
insignificant difference, however, is full proof
that the plants belong to different strains.
The union of the divergent strains seemingly
brought together pairs of hereditary color-factors
—if we hold to the Mendelian explanation — that
had been separated and hence had gone unmated
for an indefinite number of generations.
In the same way, we may suppose, I had
brought together, through a happy chance, in the
course of these breeding experiments with the
calla, two strains that bore complementary odor-
factors, the union of which released and made
tangible the latent quality of perfume-bearing,
which, in all probability, no calla of either
strain had outwardly manifested for hundreds
or perhaps for thousands of years.
—No race is perfected — no
living thing is freed from
the struggle for existence.
O gj *< ^J N^J S£oS'(**JiQ>QK.
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THE STONELESS PLUM
AN EXPERIMENT IN TEACHING
A PLANT ECONOMY
I WAS showing some specimens of the remnants
of stones in various specimens of my new
plums to a visitor one day. I indicated a
stone that was like the crescent of the new moon
in shape.
"This," I said, "is my plum as it was when
the stone was only partially taken out of it.
And this" — indicating another one with only a
fragment of stone not as large as a grain of
wheat — "is the same plum four or five generations
later."
The visitor laughed. "That," said he, "reminds
me of the museum that showed a skull labeled
The skull of William Shakespeare,' and another
labeled The skull of William Shakespeare when
he was a boy.' There is this difference, however,
that Shakespeare's head, according to the museum
record, got larger as he advanced in age, whereas
[VOLUME II — CHAPTER IV]
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LUTHER BURBANK
your plum stone became smaller." And then,
becoming quite serious, my visitor inspected a
series of fragmentary plum stones that had been
placed before him, and added:
"To make a stone grow smaller was certainly
a notable feat. How did you manage it?"
This is a question that has been asked more
often, in connection with the stoneless plum,
than in the case of almost any other of my plant
productions. For a plum which looks on the
outside precisely like any other, but which is
found to be stoneless, never fails to excite
surprise.
Even visitors who know what to expect, when
asked to bite through one of these specimens,
can seldom refrain from exclamations of wonder
when the teeth go right through the fruit as
readily as they would through a strawberry.
Many persons are not greatly interested in the
daisy that combines four specific strains, because
they know nothing of the difficulty of making such
a union, and are quite unmoved by the spectacle
of a white blackberry or a fragrant calla,
because they have seen white fruits before, and
because fragrant flowers are rather the rule than
the exception. But no one ever saw an edible
stone-fruit without a stone until one was pro-
duced here on my farm.
[106]
THE STONELESS PLUM
So "How did you do it?" is the universal
question of laymen and scientific botanists alike
on seeing this really remarkable fruit.
And when an attempt to answer the question
is made, the story seems absurdly short and
simple; yet to my mind it recalls reminiscences
of what was perhaps the most strenuous series of
experimental efforts that I ever undertook— a
quest that occupied a considerable share of my
time for a period of fifteen years, and which even
now is not altogether completed.
As you follow the outline of this story, please
recall that while it takes but a phrase to tell of
the pollenizing of two plum flowers and the
production of one anomaly in the first generation
and of some other anomaly in the second, in
reality a period of five or six years has elapsed
between the pollenizing experiment and the
observation of the second generation results.-
When this is borne in mind and it is further
recalled that breeding through many generations
is necessary to secure the results desired, it will
be clear that the production of a stoneless plum
was an achievement that required its full share
of patient waiting.
THE RAW MATERIALS
At an early stage of my almost endless series
of experiments in the hybridizing of plums, I
[107]
LUTHER BURBANK
chanced to hear of a so-called seedless plum that
was said to grow in France, where it had been
known for a long time as a curiosity. About
1890 I sent to the Transom Freres Nurseries in
France and secured twigs of this plum, which was
known merely as the Sans Noyau.
These were grafted on one of my plum trees,
and in due course produced a crop of fruit, which
as expected, proved to be a blue-black, cranberry-
sized fruit, extremely sour, soft, and unfit for
eating either raw or cooked. The original shrub,
as I have been informed, and as it grew here, is
a rambling, thorny bush rather than a tree, utterly
worthless for any purpose except the one for
which I desired it.
The fruit, besides being flavorless and unpal-
atable, was scanty in yield.
Moreover the fruit was by no means seedless,
notwithstanding its French name. It was only
partially stoneless, as most specimens produced
fair-sized kernels in the fruit, and every kernel
had a thick rim of stone around one side partially
covering the kernel. While it therefore lacked
much of exhibiting the condition of stonelessness
that I had hoped to see, it did, nevertheless, show
a tendency to abandon the stony covering that has
always characterized all the fruits of the plum
family.
[108]
A Typical Stoneless Plum
In this stoneless plum the seed, with its germinal
substance, is retained, out the stone has been almost altogether
eliminated. The resulting jruit is a plum of such unique character that
you may bite through it almost as readily as you would bite
throueh a strawberry. The produdion oj this stoneless
plum is one oj Mr. Burbank's greatest achieve-
ments. It was accomplished through a
long series oj hybridizing experi-
ments jutly explained
in the text.
LUTHER BURBANK
•
From the outset I was convinced that by
proper hybridizing and selective breeding it could
be made valuable.
Next season the blossoms of the freak plum
were fertilized with the pollen of the French
prune and with that of numerous other plums
and prunes.
The seedlings from these crosses were grafted
to ensure their earlier bearing. In the first
generation I obtained some plums fully twice as
large as their seed parent. Most of these had
stones, however, and were soft, sour fruits. A
very few of them were partially stoneless, and
from these the work was continued.
GETTING RESULTS
The next generation showed some general
improvement in the growth of the tree and the
size and quality of the fruit. All the seedlings of
the cross from the Sans Noyau upon the French
prune were grafted and fruited, even though
many of them showed the thorny, dwarfed, ill-
shaped type of tree of the uncultivated ancestor.
After two or three generations there was a
marked tendency to improvement.
In a large lot of seedlings, in 1904, I obtained
two that seemed to me of favorable appearance—
for much can be known from the quality of leaf
and stem long before the time of fruiting.
[110]
THE STONELESS PLUM
And when, two years later, the grafts thus
selected bore fruit, it was delightful to find my
predictions verified; the fruit was almost abso-
lutely stoneless, only the faintest splinter of stone
occasionally appearing. And combined with this
stoneless condition there were qualities of size
and flavor that made the fruit practically equal to
the French prune. Moreover, as is often the case
with hybrids one strain of which is wild stock,
the new plum proved to be a very good bearer.
So my ideal of an eatable plum having no
stone about its seed was almost achieved.
I say almost achieved because there still
remained, in the case of the plums of best quality,
a fragment of shell which varied from a small
crescent about one side of the kernel to an almost
invisible granule. There were some individual
plants among the numberless seedlings that bore
fruit in which the stone was absolutely eliminated
and, in some cases, the seed also.
But it proved extremely difficult to combine
this quality of entire stonelessness with the
desirable qualities of size and flavor, lacking
which the fruit could have no practical value.
Further hybridizing experiments, aimed at the
production of an absolutely stoneless plum of
fine flavor, are still under way; but in the
meantime there are several varieties actually in
tin]
LUTHER BURBANK
hand that are of most admirable quality and yet
stoneless. In the ordinary French prune, from
three to six per cent, of the entire fruit is stone;
while in my stoneless prune called the "Conquest"
the fragment of stone does not represent more
than a thousandth part of the bulk or weight of
the fruit.
And among the eight or ten hundred varieties
of stoneless plums now growing in my orchard,
there are sure to be some that will show still
further improvement.
WHY THE TASK WAS DIFFICULT
The task of producing a stoneless plum had
proved very difficult chiefly because it had all
along been necessary to bear in mind a number
of quite different objective points.
It was not sufficient to produce a stoneless
plum. From the practical standpoint there would
be no object in that unless the fruit about the
stoneless kernel was of good size and of palatable
quality. And, unfortunately, there appeared to
be no tendency to correlate stonelessness with
good quality of fruit.
In point of fact the tendency was quite the
other way; and, indeed, this was to be expected
in view of the fact that the original partially
stoneless plum was a small, acid fruit growing on
a wild bush.
[112]
THE STONELESS PLUM
The problem was to combine two lines of
ancestry that were in many respects directly in
conflict. It would have been impossible to do
this had it not proved that stonelessness and good
quality of fruit, although not originally combined,
have the attributes of what may be called unit
characters, and hence can be assembled in a
single fruit in the later generations of a hybrid
progeny.
THE ORIGIN OF THE STONE FRUITS
A very natural question arises as to what had
originally caused the little French "bullace" — as
the Sans Noyau is sometimes called — to develop
the extraordinary tendency to give up the stony
seed-covering which no other member of the
family had ever been known to renounce.
The question is doubly significant when we
recall that some sort of shell or stony covering
is almost absolutely essential to the preservation
of the seeds of plants in general. The shell is
often very thin, as with the seeds of most garden
plants. It may be reduced to a mere filament of
cellulose, as in the case of a grain of wheat.
With pulpy fruits it is usually a very significant
covering, of which the seeds of the apple and
orange afford typical examples. And with the
great tribe of fruits represented by the plums,
cherries, peaches, apricots, and almonds, this
[113]
Peach and Almond Stones Compared
This illustration shows the similarity between the
stones of the peach and the almond, at the same time
revealing characteristic differences. Some horticulturists believe
that the almond was the original stock from which the peach was developed
through selective breeding in prehistoric times. Others do not accept
this theory* but all are agreed that peach and almond are pretty
closely related, and at least have common ancestors. Mr.
Burbank made interesting experiments in hybri-
dizing the almond and the peach which
are fully described in another volume.
THE STONELESS PLUM
shell has been developed until it is veritably
stone-like in texture.
Just why this extraordinary development of
the protective seed covering was necessary or
advantageous in the case of this particular tribe
of plants, it would perhaps be difficult to say.
It is altogether probable that the original pro-
genitor of the family of stone-fruits grew in central
Asia. I have received from that region a shrub
that may perhaps be regarded as the prototype of
the entire race of the stone-fruits — not perhaps
the direct progenitor, but an early offshoot from
the ancestral stock which has remained in the
original environment and has not, perhaps, very
markedly changed from the original state during
the hundreds of generations in which the other
branches of the family were spreading southward
and westward across Asia and Europe.
If we could know just what the enemies of the
primitive Asiatic stock of the stone-fruits were
like, we could perhaps surmise the reason for the
development of the unusual seed-cover.
Perhaps the stone was necessary to protect
the kernel from the teeth of monkeys or primitive
men; perhaps it was more particularly needed as
a protection against climatic conditions, to ensure
preservation during semi-arctic winters; or to
keep vitality in the kernel during protracted
[115]
LUTHER BURBANK
periods of drought, since, unlike most other
fruits, the seeds will rarely germinate if fully
dried.
As to all this we can only surmise. But we
may have full assurance that the thick, stone-like
seed-cover served a useful purpose, else it would
never have been developed and so persistently
preserved in all the divergent races of stone-fruits
that were evolved under the new conditions of
southwestern Asia and southern Europe to which
these fruits found their way.
The roving tribes of Arabia developed a modi-
fied form of the fruit adapted for preservation by
drying, and now termed the apricot. Other
people consciously or unconsciously selected and
developed the almond; and yet others the juicy
and luscious peach; while the plum ran wild and
put forth a galaxy of hardy offspring that made
their way to the north of Europe and also, along
some now obliterated channels, to the Western
Hemisphere.
But each and all of these descendants main-
tained, and some of them like the peach intensified
and elaborated, the unique characteristic of a
horn- or stone-like protective covering for the
seed.
And so, it becomes matter for wonderment
that with all these uncounted generations of
[116]
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LUTHER BURBANK
heredity clamoring for fruit with a stony covering
there should have developed in France a member
of the tribe, even though it be an inconspicuous
outcast, that rebelled against the family tradition
and dared to produce a seed that lacked a part
of the habitual covering.
How THE FREAK ORIGINATED
As to just how this break with tradition came
about, we can perhaps make a better guess than
we can as to the precise origin of the tradition.
It seems likely that the little bullace lost the
power to produce a protective stony covering for
its seed through the impoverished condition due
to some defect in the condition of the soil in
which it chanced to grow. Unquestionably the
production of the stone makes a strong draft upon
the resources of the tree. Obviously the material
to supply this dense horny structure must come
from the soil, and in case the exact chemicals
needed are supplied in scant quantity, the shrub
might be forced to economize in producing a shell
for its fruit kernel, just as a hen is forced to
economize in the shell covering of her egg in case
lime is lacking in her food.
The same sort of economy is practiced when
the human child finds inadequate nourishment.
In such case the bones may be not only small but
defective in mineral substance, a well-recognized
[118]
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LUTHER BURBANK
type of abnormality resulting with which medical
men are familiar.
So it seems plausible that a paucity of proper
food materials was the explanation of the origin
of the original Sans Noyau.
It is in keeping with this explanation that the
Sans Noyau, is, as we have seen, a small scraggly
shrub, a mere dwarf as compared with the
average stature of trees of its family; and that
its fruit is reduced to the proportions of a small
berry, and is utterly lacking in those qualities of
sweetness and flavor that are the almost universal
characteristic of other stone-fruits.
In a word, then, it is highly probable that the
plum that supplied the character of stonelessness,
upon which my experimental endeavors in the
production of a marketable stoneless plum was
founded, was a pathological product.
I may add that many other "sports" or muta-
tions in the vegetable world that have furnished a
basis for the evolution of new races or species
may very probably have had the same origin.
UP-HILL WORK
This explanation of the origin of the Sans
Noyau makes it easier to understand the difficulties
that attended the progress of this experiment.
Had the little plum been absolutely stoneless—
so that no factor whatever bespeaking a stony fruit
[120]
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LUTHER BURBANK
remained as part of its heritage — there would
probably have been no very great difficulty in
producing through hybridization a stoneless fruit
of good quality in the second or third generation.
All experiments seem to show that the stone
condition is, as might be expected, prepotent, or,
in the Mendelian phrase, dominant.
So in crossing an ordinary plum with a stone-
less one, it was to be expected that the offspring
of the first generation would bear stone-fruit. But
the latent or recessive trait of stonelessness may
be expected to reappear in a certain proportion of
the offspring of the second generation; and the
stoneless fruit thus produced may be expected to
breed true.
Such is what might be expected provided one
were dealing with an absolutely stoneless plum
as one of the progenitors.
But unfortunately we are not dealing with an
absolutely stoneless plum, but only with one in
which the tendency to produce a stone has been
minimized or partially suppressed. And so our
relatively stoneless plum of the second generation
still retains traces of the hereditary propensity to
produce the stony covering; and, as we have seen,
this propensity manifests itself in the fragmentary
stone, sometimes reduced to a mere speck in size,
that many of my stoneless plums exhibit.
[122]
THE STONELESS PLUM
Nevertheless there remains not a doubt that
from subsequent generations, from the stock in
hand, an absolutely stoneless plum that retains all
the valued qualities of the fruit and in all sizes,
colors and flavors desired will be produced.
That it has been possible to eliminate the
stone altogether, advancing thus markedly in this
regard upon the original partially stoneless form
with which the experiment began, suggests the
truth of a view now held by some prominent
biologists, notably by Professor William E. Castle
of Harvard, that a unit character may be modified
in successive generations — not merely blended or
made into a mosaic with other characters, but
actually modified as to its potentialities.
Professor Castle instances in support of this
view the case of guinea pigs bred by him that
developed a full-sized fourth toe on the hind foot
from a rudimentary stump of a toe.
The experiments just cited illustrate the oppo-
site condition of causing a rudimentary organ —
in this case a plum stone — to be altogether
eliminated.
It should not be overlooked that both experi-
ments are perhaps capable of interpretation in
other terms. In each case what actually happens
may perhaps be better explained as reversion to
a very remote ancestor. Doubtless there were
[123]
LUTHER BURBANK
among the ancestors of the guinea pig races with
four toes; and doubtless if we go far enough
back we should find ancestors of the plum that
produced a seed having no stony covering. And
we are perhaps not far wrong in assuming that it
was the long-subordinated influence of this vastly
remote ancestor that, in the case of my plums,
sided with me, so to speak, against the forces of
the more recent heredity, and made possible the
ultimate success of my hybridizing experiments.
THE VALUE OF THE NEW PRODUCT
We are so accustomed to putting up with the
annoyance of the stone in the fruit that we for
the most part never give it a thought. But a
moment's reflection makes it clear that the plum
stone serves man no useful purpose, while the
inconvenience it gives us is obvious.
It requires no argument to show that a solid
fruit without a stone would be far more accept-
able.
But this is not the only reason, although
perhaps a sufficient one, for the development of
the stoneless fruit. The other reason looks to
economy of production and saving of material
from the standpoint of the tree itself. It has been
estimated that a tree requires several times as
much solid material and the expenditure of far
more energy, to produce the stony covering of
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LUTHER BURBANK
the fruit seed than to grow the flesh of the fruit
itself.
So it might well be expected that other things
being equal, a tree bearing stoneless fruit would
prove at least twice as productive as one bearing
stone-fruit.
Under the conditions of nature, this increased
fruitage would by no means compensate for the
loss of the protective stony covering, for the seed
unprotected by its coat of mail would be at the
mercy of any bird or animal or insect that
attacked it.
There would probably be no representative of
the stone-fruit family in existence to-day were it
not for the protection afforded the seed by its
hard and indigestible covering.
Regardless of animate foes, the seed would
perish from the effect of sun, wind, rain, and
frost, if denied protection.
And this is by no means a mere matter of
inference. One of the great difficulties that
attended the experiments which I have just
narrated, was the preservation of the stoneless
seeds from one generation to another. It was
found to be exceedingly difficult. Various insects,
especially aphides, millipedes and eel-worms,
would get among them and quickly destroy them.
Fungous diseases also attacked them. And for
[126]
One Result oj Stonelessness
The picture on page 12$ showed the normal attachment oj
the stem to the stone oj the Jruit. The stoneless plum obviously
lacks this support. Hence ij the plum is very large the flesh may be
drawn out at the point oj attachment oj the stem by the weight of
the Jruit, thus pulling the plum out oj shape, as shown in
this figure. So strength of skin and firmness oj
texture are points that Mr. Burbank
must bear in mind in developing a
new race of stoneless fruits.
LUTHER BURBANK
several years more than three-fourths of the seeds
kept for planting were thus lost.
At a fairly early stage of the experiment I
had large quantities of seeds in hand, for I was
operating on an expansive scale in order to have
wide opportunity for selection. Several hundred
thousand plum seeds, all stoneless, were once
placed in cold storage, at freezing temperature,
as soon as they were gathered and cleaned. Some
were placed in sterilized sawdust, and some in
charcoal dust, and some in sand.
Another assortment, similarly packed, was
kept in boxes in a cool shady place until the first
of January, when all were planted. In both lots,
the seeds that had been kept in sand were in
better condition than those preserved in the
sterilized redwood sawdust. Those kept in char-
coal differed little from the other lots. The ones
in cold storage had suffered from blue mold
more than the others, but both lots were in fair
condition.
All were planted on the same day in rows side
by side. The seeds that had been kept in cold
storage germinated at once, and in a week were
all practically above ground. The seeds of the
other lot, which had come from the same trees,
did not commence to germinate for about six
weeks. Yet later in the season very little differ-
[128]
LUTHER BURBANK
ence could be seen between the two lots; on the
whole the cold storage seeds showed rather the
poorer growth.
FURTHER IMPROVEMENTS OF METHOD
An even better method of preserving the seed
was presently developed, and I was finally able to
preserve the stoneless seeds almost as securely as
if they had their original protective covering.
My new method consists in washing the
stoneless seeds in clear fresh water when first
removed from the fruit; immersing them for a
few minutes in a week solution of "Bordeaux
mixture" (sulphate of copper and lime-water),
then rinsing for a brief period in fresh water, and
placing them in damp sawdust that has been
sterilized by boiling, care being taken that the
sawdust is barely moist, not wet. The box con-
taining the seeds is placed on the north side of a
building, in a cool, shady place, and examination
is made from time to time to see that the seeds
do not become too dry or infested with insects or
mold.
If treated in this way, the seeds are practically
all saved; they may be planted out df doors
like other plum seeds, and they will germinate
promptly.
It is obvious that a seed requiring such careful
treatment to preserve it all the winter would
[130]
Another Stoneless Plum Compromise
Here the cavity left by an eliminated stone is filled by en-
larging the seed itself. This is not desirable from the standpoint
oj the horticulturist, but it is one way of overcoming the defect of a large
cavity within the fruit* which necessarily weakens the structure
of the fruit itself. Further breeding experiments may
reduce the size of the seed while increasing the pulp
in such a way that no cavity will remain.
LUTHER BURBANK
stand small chance of being able to perpetuate
its kind in a state of nature. But on the other
hand, it must be admitted that it is well worth
while to give the amount of attention required to
the preservation of these seeds, in view of the
enhanced value of their product.
It will be understood, however, that the aver-
age fruit-grower will not be required to concern
himself about the seeds, as his orchards will be
propagated by grafting in case of this fruit as is
customary with all orchard fruits.
There can be little doubt, then, that the time
is almost at hand when all our plums will be
grown without stones, since the experiment of
removing the stones from a large number of
varieties can now be followed up without great
difficulty.
The pioneer work has been done, and the cross
breeding of my best present varieties of stoneless
plums, to secure all the desirable qualities of any
existing plum, may readily be effected.
Even though the fruit should not be of better
quality than that which it supplants, the fact that
the elimination of the stone permits an increased
abundance of fruit, to say nothing of the value of
the stoneless fruit itself, will offer an inducement
that the progressive fruit raiser will find con-
clusive.
[132]
Many Plums on One Tree
A typical branch of a plum tree in Mr. Burbank's
orchard. Growing within easy reach are Jour or five varieties oj
plums that are very different Jrom one another in size and Jorm and
color* as well as in quality oj flesh. Oj course these plums are oj
quite different ancestry* and they would not have grown
normally on the same tree. But Mr. Burbank grafts
dons oj many stocks on the same branches*
to economize space. Several hundred
varieties may be jound growing
Jrom a single trunk.
LUTHER BURBANK
It should be added that the plum which has
been induced to vary in the matter of seed pro-
duction, is not always content merely to have cast
out the stone but sometimes tends to eliminate
the seed itself.
THE SEED ALSO MUST Go
One of my stoneless plums has nothing but a
jelly-like substance to take the place of the seed.
It is probable that plums actually seedless as well
as stoneless will prove favorites with some fruit
growers.
Of course plums that present this anomaly
cannot be propagated from the seed. But in
this regard they do not differ from a number of
cultivated plants, including the potato, the horse-
radish, and the sugar-cane. And for that matter
it must be recalled that very few orchard fruits
are reproduced from the seed. The favorite
varieties of apples and pears are so blended that
they do not breed true from the seed. If you
were to plant the seed of a Baldwin apple, a
Bartlett pear, or a sugar prune, there is only
the remotest chance that you would produce a
seedling that would resemble the parent.
Yet apples and pears and prunes are prop-
agated year after year by means of buds and
grafts. The same method of propagation would
of course suffice for the seedless plum.
[134]
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LUTHER BURBANK
It would still be possible, however, to produce
new varieties of seedless plums by using the
pollen of these varieties to fertilize the flowers of
other plums that were stoneless but not seedless.
The seedlings from such a cross would tend to
vary in successive generations, as all hybrids do.
A certain number of the offspring of the second
and later generations would doubtless be seedless,
and it would thus be possible to develop new
varieties of seedless fruit from a parent stock that
is itself incapable of producing viable seed.
The stoneless hybrids already produced repre-
sent almost every color of the plum — white, pale
yellow, orange, scarlet, crimson, violet, deep blue,
almost black, striped, spotted, and variously
mottled. They vary indefinitely in quality. Some
of them are of abnormal size. They ripen from
the middle of June until Thanksgiving.
So the stoneless plum already constitutes a
new race having numberless varieties, and the
possibilities of further improvement are limitless.
— 7n producing stoneless
fruits, we are simply
helping plants to catch
up with evolution.
THE ROYAL WALNUT
SPEEDING THE
GROWTH OF A LEISURELY TREE
IF ON visiting my grounds you were to notice
two trees, one ten times as large as the other,
growing side by side, you would perhaps be
surprised to be told that the two are of the same
age and grew from seed of the same parent. And
it perhaps would not greatly clarify the matter
in your mind to be told that these are varying
individuals of a remarkable hybrid known as the
Paradox Walnut.
But probably your interest would be aroused
in a tree that could show such diversity of
progeny.
The tree in question was developed more than
twenty-five years ago. One of its parents was
the native California black walnut tree; the
other parent was the European tree usually called
the English walnut, but with somewhat greater
propriety spoken of as the Persian walnut.
[VOLUME II— CHAPTER V]
LUTHER BURBANK
The European tree had been introduced in
California a number of years before the time of
my experiments, and it thrives in our climate and
produces abundant fruitage. I had heard of a
supposed natural European hybrid walnut, and I
determined to make the experiment of fertilizing
the flowers of the California species with pollen
from the Persian.
The experiment itself presented no particular
difficulties and the results were of a striking
character.
The nuts that grew from the hybridized
flowers were to all appearance unchanged. This,
of course, is quite what might have been expected,
for the influence of foreign pollen on the ovum
of a plant manifests itself in the innate qualities
of the seed, and not in the exterior qualities of
the fruit immediately produced. But when the
hybrid nuts were planted the following season,
a part of the seedlings that sprang from them
showed at once the effects of the intermingling of
racial strains.
As compared with seedlings of either the
California or the Persian walnut, they manifested
an enormously enhanced capacity for growth.
Indeed they sprang forward at such a rate as
presently to dwarf their pure breed relatives.
The phenomenal growth of these hybrid trees
[138]
A Sixteen Year Old Paradox
At sixteen years of age, Mr. Burbank's new Paradox
walnut trees were sixty feet in height and as much in breadth
of branches — the trunk being two Jeet in diameter at about four feet
from the ground. Meantime English ivalnuts on the opposite
side of the street averaged only eight or nine inches
in diameter at thirty-two years of age, and
had a spread of branches only about
one quarter that of the
youthful Paradox.
LUTHER BURBANK
continued year after year. The tree so far out-
stripped all competitors in the matter of growth
that it might fairly be said to represent a new
type of vegetation.
On this account, and in recognition of sundry
other anomalies, I named them Paradox.
At sixteen years of age these trees were sixty
feet in height and as much in breadth of branches,
the trunk being two feet in diameter at about four
feet from the ground. Meantime English walnuts
on the opposite side of the street averaged only
eight or nine inches in diameter at thirty-two
years of age, and had a spread of branches only
about one-fourth that of the youthful Paradox.
In addition to its quality of rapid growth, the
Paradox has wide-spreading branches with a
tendency to droop. It makes a beautiful shade
tree. The leaves are of extraordinary length,
sometimes measuring three feet, although usually
only about half that. Another curious charac-
teristic is that the foliage has a delicious apple-
like fragrance, of which the foliage of the parent
tree gives no suggestion.
These anomalies of growth and foliage show
the mingling of racial strains. A further result
of this mingling is shown in the fact that the
hybrid tree produces very few nuts. It is obvious
that the two strains brought together are so variant
[140]
The Blossom oj the Walnut
The walnut, like many other trees, is a wind loving plant
and depends upon the swish oj its branches in the breezes and
the breezes themselves to carry its pollen Jrom limb to limb and
tree to tree. The direct color photograph print shown here is
that of the pistillate, or pollen-receptive blossom oj the
walnut tree, upon whose slightly sticky surjace the
flying pollen finds lodgment, its grains fer-
tilizing the seed, combining with it
to produce a crop of walnuts,
LUTHER BURBANK
that their progeny is made relatively sterile. The
sterility is not absolute, however, for the few nuts
produced germinate readily if planted.
But another anomaly manifests itself in the
characteristics of the seedlings thus produced;
for these are the ones that show such extraordi-
nary variation in size.
In the same row, as already intimated, there
will be bush-like walnuts from six to eighteen
inches in height side by side with trees that have
shot up to eighteen or twenty feet; all of the same
age and grown from seeds gathered from a single
tree. This rate of growth continues throughout
life, and the fraternity of dwarfs and giants has
been a puzzle to layman and botanist alike.
These second generation hybrids vary as much
also in regard to foliage and general characteristics
of form and development as in size. Some resemble
the California walnut, others the Persian ancestor,
and there are scores of variations, the manner of
growth of some of which — notably those that
trail their limbs along the ground like a gourd or
squash — bears scant resemblance to that of any
walnut. From this extensive variation, it has
been possible to select trees of even more rapid
growth than the second generation hybrids, and
the field seems to be open for the production,
through selection in successive generations, of
[142]
THE ROYAL WALNUT
trees of still wider diversity of form and growth.
Curiously enough the wood of the Paradox
walnut is exceedingly hard, even harder and more
close-grained than that of the ordinary black
walnut. This is surprising in view of the rapid
growth of the tree. Ordinarily trees that grow
rapidly have soft wood, as every cabinet-maker
knows.
The Paradox further justifies its name by
producing a wood that has great firmness of
texture and is well adapted to take on a cabinet
finish.
All in all the production of the Paradox hybrid,
and the development of a race of hard-wood trees
of exceedingly rapid growth, constitutes a genuine
triumph in tree culture. A tree that grows to
the proportions of a handsome shade tree and
furnishes material for the cabinet-maker in six or
eight years, has very obvious economic import-
ance.
THE ROYAL WALNUT
At about the same time when the Paradox was
produced, I undertook another series of hybrid-
izing experiments with walnuts that resulted in a
tree scarcely less anomalous.
These experiments consisted of the mating of
the California walnut with the black walnut of
the Eastern United States. The latter tree pro-
[143]
A January i Walnut Grajt
The walnut graft shown above was made by Mr.
Burbank on January /, 79/3, and, as can be seen, was at that
time but a tiny cion.
\
The Same Graft Six Months Later
The color photograph print above shows the rapid
progress made by the grafted cion pictured opposite. This
photograph was taken on July i, 1013, six months
to a day after the grajt was made.
LUTHER BURBANK
duces perhaps the finest cabinet wood grown in
America, but it has almost disappeared from our
eastern forests owing to the rapacity and lack of
foresight of the lumberman. The California and
eastern walnuts are rather closely related, yet
the divergence is sufficient to give the hybrid a
character markedly different from either parent.
In some respects this hybrid, which was
christened the "Royal," showed characteristics
analogous to the Paradox. It had the same
tendency to extraordinarily rapid growth, and in
subsequent generations it showed the same
tendency to produce a varied company of dwarf
and of giant progeny. There was also a consid-
erable variation in foliage, although not the
extraordinary diversity shown by the second
generation seedlings of the Paradox.
In one important respect, however, the Royal
hybrid differed fundamentally from the other.
Instead of being relatively sterile, it showed the
most extraordinary fecundity. The first genera-
tion hybrids probably produce more nuts than
any other tree hitherto known. At sixteen years
of age one of these trees produced a harvest of
nuts that filled twenty apple boxes, each about
two feet long by one foot in width and depth.
In one year I sold more than a thousand
dollars worth of nuts from a single tree.
[146]
THE ROYAL WALNUT
The nuts themselves are closely similar in
appearance to those of the parent trees, but
are individually larger. Unfortunately seedlings
grown from the nuts cannot be depended upon to
reproduce all the good qualities of their hybrid
parents. Like most second generation hybrids,
they tend to "throw back" to the divergent
grandparental strains.
To propagate the race extensively, therefore, it
is advantageous to adopt the well-known method
of grafting.
It has been found that root stocks of the Royal
hybrid furnish very valuable stocks on which to
graft the English walnut in California. On most
soils a tree grafted on this hybrid will produce
several times as many nuts as a tree of corre-
sponding size growing on its own roots. The
trees are also much less subject to blight when
they are thus grafted.
GRAFTING THE WALNUT
The importance of the new walnut and the
fact that it may best be propagated by grafting
makes it desirable to add a few details as to the
method by which grafting is effected; for in the
case of this tree the process is far more difficult
than with ordinary fruit trees.
Grafting the walnut is not, indeed, as difficult
[147]
LUTHER BURBANK
as grafting the pecan or the hickory, with both of
which species the process was until recently
found impossible of accomplishment. In this
regard the walnut is rather to be likened to the
fig, both being difficult to graft, yet not presenting
insuperable difficulties for the skilled operator.
Persons who first attempted to graft the wal-
nut in California often failed four times out of
five; and budding was even less successful. But
the importance of the subject led to a careful study
of methods, and today grafters who thoroughly
understand their work are so successful that they
scarcely have more than two or three failures in
a hundred successful grafts.
To attain such success, however, it is necessary
to attend carefully to the various stages of the
process. The grafting should not be attempted
until quite late in the season; just after the buds
begin to start is the most opportune moment.
Hard wood should in all cases be selected for
grafting; the pithy tips are utterly worthless for
this purpose. Some grafters claim that only about
two cions should be used from the base of the
last year's growth where the wood is very firm.
Of course the principle of fitting the inside
bark or cambium layer of stock and cion accu-
rately together applies here as in the case of
every other tree. Further details of the method
[148]
Wood of the Paradox
It might naturally be supposed that the Paradox would
produce a sojt wood like that of most quick-growing trees.
Such is not the case, however. The wood of the Paradox is as hard,
almost, as that of the black walnut, and has the
beautiful walnut grain shown in the
photograph print above.
LUTHER BURBANK
will be given in a subsequent chapter, where the
special methods of grafting and budding will be
more fully examined. It suffices for the moment
to emphasize the fact that these methods of
propagation are as advantageous in the case of
the walnuts, whether hybrid or of pure strains, as
in the more familiar case of fruit trees.
Of course the stocks on which to graft must be
grown from nuts, and I have already pointed out
that the seedlings are likely to show diversity.
But all that is necessary is to plant the seeds
rather thickly, and then to save the seedlings that
show the best qualities.
STARTING A WALNUT ORCHARD
A practical method of producing a permanent
and profitable orchard with a foundation to last
for a century, is to plant some seeds of the Royal
hybrid in groups of three or four at intervals of
fifty feet each way. By the end of the first season
the strong growers will have asserted themselves,
and the others can be weeded out. There will
almost surely be at least one good tree in the
group. Failing that, there will be other groups
in which there are extra seedlings of good quality
that may be transplanted.
The seedlings should be allowed to grow for
four or five years, the ground about them being
cultivated and may be used for crops of corn,
[150]
Two Inches in Diameter in One Year
The cross section of a Paradox walnut trunk pictured
above shows the annual rings oj the treet or its yearly growth.
The photograph is made exact size, and it will be noted that some
of the markings are an inch apart, thus showing that
the tree increased in diameter two full
inches within the year.
LUTHER BURBANK
potatoes, beans, or pumpkins, but preferably not
sown with grain, lest the growth of the trees be
checked.
At the end of five or six years there should be
a fine walnut orchard with trees having trunks
three to six inches in diameter.
Now the stock is ready for grafting. The stock
branches selected for this purpose should not be
over two or three inches in diameter. The cions
grow rapidly and an orchard produced in this
way surpasses all others. Its trees have a natural
black walnut vigorous system of roots, with
undisturbed tap root. A year's growth has been
saved by not transplanting, and a start equivalent
to the growth of several years has been gained by
using the faster-growing hybrid.
So the English walnut grafted on this stock
becomes a producing tree at a very early age, and
an orchard of English walnuts thus grafted is
worth at least twice as much as one on its own
roots.
The tree thus grafted has not only the advan-
tages mentioned, but it is more wide-spreading
and therefore more productive than the original
tree; and the spread of limb is duplicated by the
root system, which thus ensures a good supply of
nourishment and the capacity to produce large
crops even in dry seasons.
[152]
Variation in Walnut Leaves
As in his work with all other plants, Mr. Burbank pays
strict attention to the selection of those seedlings which have
the most and the best leaves, and the best leaf formation. Many
seedlings, promising in other respects, have faulty leaves,
and promptly go to swell the bonfire of rejected
plants which Mr. Burbank burns every
few months.
LUTHER BURBANK
We have seen that the hybrid walnuts of
both the Paradox and the Royal types have the
peculiarity of producing trees of quick growth
and gigantic stature in the first filial generation,
and a mixture of dwarfs and giants in the second
generation.
THE STRANGE TRAITS OF HYBRIDS
The tendency to surpass their parents in
size is a characteristic that is very commonly
manifested when plants of different species are
hybridized. It is a familiar and now well-
recognized fact that the crossing of diverse
strains of living creatures, plant or animal, tends
to result in what for lack of a better term is
usually described as increased vitality.
It would appear as if the conflict of new
tendencies so stimulates the cellular activities as
to give them an unwonted capacity for repro-
duction.
In this case we are not concerned, as we were
in some of the other hybridizing experiments
already examined, with the prepotency or domi-
nance of the qualities of one parent. Instead of
this there is a distinct blending of characteristics
so that the new product is in many respects inter-
mediate between its parents in matters of foliage
and fruit. But in growing capacity it far surpasses
them both.
[154]
LUTHER BURBANK
Thus we have produced, as the offspring of
the slow-growing English walnut and the not very
rapidly growing California species, a tree that
grows so rapidly as presently to tower far above
either of its parents.
As to form of leaf and fruit the hybrid may
resemble one parent in one direction and the
other parent in another. The leaf of the Paradox
walnut, for instance, more closely resembles the
leaf of the English parent. The outside appear-
ance of the Paradox nut is also similar to that of
the English walnut. But on breaking the shell
we find that it is thick and strong like the
shell of the American species, and the kernel is
relatively small, quite different in form as well as
in flavor from that of the English walnut.
It cannot be said that any one has a very clear
notion as to precisely what the changes are that
give to a hybrid race this enhanced vitality. But
this mystery is after all only part of the great all-
pervading mystery of heredity, which in turn is
merged with the mysteries of life processes in
general.
WHY SOME ARE DWARFS
What I shall consider a little more at length
here, however, is the conduct of the seedlings
of the second generation grown from either the
Royal or the Paradox hybrids.
[156]
Some English Walnuts
Mr. Burbank's Paradox walnuts very closely resemble
the English walnuts shown here, but instead oj having thin
paper shells like these, they have the thick, woody shell of the
black walnut. The Paradox, however, was not selected as
a nut-bearing tree, but as a quick-growing lumber tree.
It produces very feiv nuts, in fact, but such as are
produced will germinate readily if planted.
LUTHER BURBANK
How does heredity explain the observed fact
that some of these are dwarfs that can by no
process of urging be made to attain anything
like the average stature of walnuts in general,
whereas others, sprung from nuts grown on the
same stalks, are giants that surpass even their
hybrid parent, not to mention their moderate-
sized grandparents. The fact of this diversity is
unquestionable. It affords a surprise to all who
inspect the trees of this strangely diversified
fraternity.
But how explain it?
A clue to the explanation is gained when we
learn that the California walnut, which, it will be
recalled, was a parent form in each of the hybrid
strains, is a tree showing great variability in the
matter of size when growing in a state of nature.
In the northern and central parts of California
it is usually a large spreading tree, often with
gracefully drooping limbs. But farther to the
south it becomes a mere shrub, and on the moun-
tains and hills about Los Angeles it is only a bush.
The nut diminishes in size correspondingly until,
in Texas and Mexico, it is scarcely larger than
a pea.
When growing still further to the south, in
New Mexico and Texas, the black walnut is some-
times classified as a different species.
[158]
THE ROYAL WALNUT
It appears to me, however, that these dwarfed
southern forms are only varieties that have
acquired different characteristics through the
influence of what for them has proved an unfa-
vorable environment. In any event there is no
reason to doubt that the dwarf form and the
relatively large one are descended from the same
original stock, though doubtless divergence has
gone on through numberless generations.
Meantime the English or Persian walnut, the
other parent of the Paradox, is also a variable
tree. In its native home it is very small, and even
the cultivated variety cannot be depended upon
to reproduce a given racial strain when grown
from the seed.
It is obvious, then, that the tendency to dwarf-
ness, which appears in such conspicuous fashion
in some of our second generation hybrids, may be
accounted for as reversion to dwarfed ancestral
strains in both parents in the case of the Paradox
and of one parent in the case of the Royal.
The tendency to grow relatively large prevailed
in the strains of walnuts that were used in my
hybridizing experiments, and the prepotency or
dominance of this tendency is clearly shown in
the hybrids of the first filial generation. But the
latent tendency to dwarfness, which in the Men-
delian phraseology would be termed a recessive
[159]
LUTHER BURBANK
trait, is able to reassert itself in a certain number
of the offspring of the second filial generation,
causing these to "throw back" to their dwarfed
ancestors in the fullest measure.
The capacity for large growth has been abso-
lutely left out of their individual make-up.
In the Mendelian phrase they are pure reces-
sives; or, using the more technical terminology,
they are "homozygous" as to the hereditary
factors or determiners of the unit character of
dwarfness.
The reader may or may not feel that the new
terminology adds to our comprehension of the
phenomena. But in either case the fact of the
appearance of the dwarf specimens of the second
generation among the hybrids is at least in a
sense explained by our knowledge that there were
dwarfs in their ancestry.
How ACCOUNT FOR THE GIANTS?
But while we are thus supplied with a more
or less satisfactory explanation of the appearance
of the dwarf hybrids, the colossal companions of
the same generation are as yet unaccounted for.
It is a familiar fact, as just pointed out, that
hybrids of different species do tend to take on
new capacities for growth. But what hereditary
warrant have the upstarts for thus out-doing
[160]
A Grafted Walnut Stump
When Mr. Burbank began his experiments with the
walnut, he found that those who attempted grafting this tree
Jailed at least four times out of Jive, and that budding was even less
successjul. By giving carejul attention to the various stages
of the process, as explained in the textt he was able
to make successful walnut grafts in large
quantities, averaging only two or three
failures to one hundred grafts.
LUTHER BURBANK
their parents? So far as we are aware, there is
no record of a pure bred walnut of any of the
three species involved that ever showed such
capacity for rapid growth or such propensity to
continue growing until it attains colossal propor-
tions as the hybrids manifest.
There is no recorded or observed ancestor
to whom we can appeal in explanation of the
development of these new races of giants.
As yet we are not denied at least a hypothetical
explanation that may perhaps account for the
observed colossal growth of these new races of
trees. The explanation demands that we go back
in imagination through very long periods of time,
and consider the ancestors of our walnuts not
merely for hundreds of generations but for
thousands or perhaps for millions of generations.
It is necessary, in short, to trace backward the
ancestral history of the walnut to those remote
epochs when the primordial strain from which
the present trees have developed grew in tropical
regions, and, in common with tropical vegetation
in general, doubtless acquired the habit of luxu-
riant development.
It is permissible even that we should place in
evidence the exuberant vegetation of that remote
geological era known as the Carboniferous Age.
In that time, as the records in the rocks
[162]
llh 3f
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BR.|Ss.|B' 3->"
^il^r0 •s.o
LUTHER BURBANK
abundantly prove, the conditions of climate now
restricted to the tropics prevailed even in the
temperate zones, and the vegetable life was char-
acterized by the abundant production of colossal
forms.
In successive ages the climate changed, and
it became necessary for the plants that were
unable to maintain existence under the changed
conditions to adapt themselves in size and in
structure to a less bountiful supply of food-stuffs
drawn from both soil and air; for the soil of the
temperate zone is relatively arid, and the air
probably became progressively less rich in car-
bon, owing to the permanent storage of vast
quantities of this substance in what ultimately
became the coal beds.
So it came about that all the descendants of
the colossal plants of the Carboniferous Era
formed races that were dwarfs by comparison.
Here and there a straggling species, like the
California redwoods, preserved a reminiscence of
its imposing heritage. But in general the trees
that make up our forests in the temperate zone
are but insignificant representatives of a lost race
of giants. These, then, are the remote ancestors
that may be invoked in explanation of the rapid
growth and relatively gigantic stature of our
hybrid walnuts.
[164]
Some Japanese Walnut Variations
In his experiments, Mr. Burbank has not only gone east
jor the English walnut, which is in reality the Persian walnut,
but he has gone west to Japan and China Jor the walnuts which grow
there, in seeking out new characters to combine with the native
California walnut. The nuts shown in the color photograph
print above are variations found among the Japanese
branch of the species and illustrate clearly the
changes in appearance as well as in other
characteristics which long continued en-
vironment works in plants.
LUTHER BURBANK
In this view the exceptional growth of these
hybrids betokens reversion to remote ancestral
strains that for countless generations have not
been able to make their traits manifest, but which
have always transmitted these potentialities as
submerged and subordinated tendencies. The
admixture of the divergent racial strains — one
from Europe, the other from California, or in the
case of the Royal, from origins separated by the
breadth of a continent — sufficed to bring together
factors of growth that for all these generations
had been separated, and the atavistic phenomenon
bf a giant walnut came into being.
Thus interpreted, the case of the big walnut
is not dissimilar to the case of our white black-
berries or to that of the fragrant calla.
In each of these instances, as in that of
numberless others that we shall have occasion
to examine, a mixture of racial strains brings
about a reversion to the structure or quality of
a remote ancestor.
In the case of the walnuts we have had
occasion to go back a few thousand generations
farther than in the other cases, but there is ample
warrant for believing that nature sets no limit on
the length of time throughout which a submerged
character may be transmitted, with full possi-
bilities of ultimate restoration.
[166]
r»s-s5*?>
I
LUTHER BURBANK
We shall have occasion to examine further
evidence of the truth of this proposition, drawn
from a quite different field, in a later chapter.
Here, for the moment, we may be contented
merely to place our colossal walnuts in evidence.
Towering above their dwarf blood-sisters, they
present a vivid object lesson in heredity that
appeals directly to the senses and strangely stim-
ulates the imagination.
— Nature sets no limit on
the length of time through-
out which a submerged char-
acter may be transmitted.
THE WINTER RHUBARB
MAKING A CROP
FOR A HIGH-PRICED MARKET
MORE than one enthusiast has declared
that the most important garden vege-
table that has been introduced to the
world in the past half century is the giant winter
rhubarb.
This no doubt is an over estimate, if for no
other reason than that it overlooks the Burbank
potato. Still, there is no question that my winter
rhubarb has proved to be of very great economic
importance. Although introduced quite recently,
it has already made its way to all quarters of the
globe, and it has proved of unusual value in
regions where no other rhubarb had hitherto been,
or could be grown.
At the Cape of Good Hope, for example,
efforts to grow rhubarb had been made for a
century at least, and always without success; but
the new variety proves an especially satisfactory
[VOLUME II— CHAPTER VI]
LUTHER BURBANK
crop there, as elsewhere, in warm, arid climates.
The plant has aroused very unusual interest
in conservative Great Britain, where the older
varieties thrive and have been extensively grown,
specimens having been obtained direct from my
plantation by Robert Holmes, a member of the
Royal Horticultural Society, and others. The
royal gardens of England are now supplied
with it.
Meantime the Emperor of Japan and the King
of Italy obtained it directly from my gardens, and
the plant has been taken back to its original home
in New Zealand, whence the original stock came,
and in its improved or, one might better say,
metamorphosed condition, it now finds favor
there, whereas its ancestral form was justly
regarded as a plant of no importance.
THE QUALITIES OF THE NEW RHUBARB
It must not be supposed that this widely
extended approval of the rhubarb is dependent on
any mere caprice. It is based on qualities of the
most enduring and substantial character. Other-
wise, it would not have been possible to plant
thousands of acres of this crop in California and
to find a ready market for the entire product in
the eastern United States. In point of fact, so
eager has been the market that the rhubarb has
been quite often called by its growers the "king
[170]
Crimson Winter Rhubarb
This picture shows that Mr. Burbank's new winter rhu-
barb retains the characteristic Jorm of the stalk of the ordinary
rhubarb, and its general appearance* except that the new form has a more
uniform tendency to redness of color. The peculiarity of the new
plant here shown is that it puts forth its stalk in the winter
at a time when the ordinary rhubarb is dormant.
The original plant from which this new
variety was developed was imported
by Mr. Burbank from
New Zealand.
LUTHER BURBANK
mortgage lifter." More than one substantial
fortune has been made by growing it here in
California and shipping it to the eastern States
during the holiday season when fruits and green
vegetables are relatively scarce.
It retains, as to general appearance, the aspect
of a greatly enlarged stalk of the familiar rhubarb
or pieplant of the eastern vegetable garden. But
the stalks are of a characteristic rich crimson
color, and as brought to the table the sauce made
from them is not only delicious in flavor, sug-
gesting the strawberry and raspberry, but it is
quite devoid of the stringiness or fiber-like texture
and the disagreeable "ground taste" of the
ordinary pieplant.
Many people who have hitherto regarded pie-
plant as a plebeian dish to be avoided are
enthusiastic in the praise of the new product.
The crimson winter rhubarb produces not
only far larger stalks than the old New Zealand
prototype, but at least ten times as many of them
to each plant. The stalks begin to appear in great
abundance early in September and continue to
produce a product of unvarying quality for eight
to twelve months together— in California through-
out the entire year — instead of for a few weeks
in the spring. So the popularity of the winter
rhubarb from the standpoint of the grower as well
[172]
THE WINTER RHUBARB
as of the dealer and consumer, is not hard to
understand.
It may be added, as further evidencing the
unusual qualities of the new plant, that it grows
in almost any soil, although giving quick response
to good conditions of cultivation like the older
varieties; that it propagates readily from root
division and under these circumstances breeds
altogether true to the perfected type; and that it
is hardy and requires no unusual attention, so that
any amateur may grow it in his garden even more
readily than he grows the ordinary rhubarb.
It must be understood, however, that the plant
cannot thrive in latitudes where it is buried under
snow, as the steady production of leaves appears
to be essential to its very existence.
In the colder parts of California it does indeed
cease to grow actively in the heart of winter, but
even then it submits to adverse conditions reluc-
tantly, if the phrase may be permitted; that is,
that it stops putting forth new leaves only when
the conditions are exceedingly unfavorable and
immediately resumes new growth when the
slightest change for the better in the weather
occurs.
THE ORIGIN OF THE WINTER RHUBARB
The importance of the new plant, and its wide
departure from the traditions of the rhubarb
[173]
LUTHER BURBANK
family, might lead one to suppose that the pro-
duction of the new variety had been a task of
great difficulty. Perhaps from the standpoint of
the average plant breeder it could hardly be
said that its creation was altogether easy; yet
compared with some of my other plant develop-
ments the production of this one was at least
relatively simple.
The original stock from which the new variety
was developed, came to me from the antipodes.
It was sent by the firm of D. Hay & Son from
Auckland, New Zealand.
The first two or three shipments were lost, as
the plants died on the way, but at last I obtained
half a dozen very diminutive roots that showed
some signs of life. These, as anticipated, produced
stalks during the winter instead of following the
conventional rhubarb custom of putting forth
stalks for only a few weeks in the spring.
The stalks of this original winter rhubarb,
however, were very small — about the size of an
ordinary lead pencil — and certainly not worth
cultivating for immediate use, as they would
have proved quite unmarketable. The plant was
admitted to have no great value in New Zealand.
Indeed, in point of quality of stalk the imported
plant berc no comparison with ordinary pieplant
of our gardens.
[174]
The Blossom oj the Rhubarb
, .TAf illustration shows the inconspicuous character of the
individual blossoms oj the rhubarb, and the way in which they are
massed together, as is usual with very small flowers. In hybridizing the
rhubarb it is only necessary to dust one head oj flowers against
another. Of course self-fertilization may take place in
many coses, and it will be necessary to examine
the seedlings themselves to determine
which ones are hybridized.
LUTHER BURBANK
It was solely and exclusively the quality of
winter-bearing that made the plant appeal to me
and suggested to me the possibility of developing
from it a valuable addition to our list of garden
vegetables.
My original stock of half a dozen plants soon
increased to a hundred or more. These plants
produced seed abundantly in successive years,
and all this seed was carefully planted and the
seedlings that grew from it, to the number of
hundreds of thousands, were closely examined
and tested as to various desirable qualities.
From among the thousands I was able to select
here and there a plant that showed exceptional
qualities of growth, standing well up above its
companions of the same age. Of course selection
was made of the plants showing this exceptional
virility, and in the course of a few years I had thus
developed, by persistent selection, a race of plants
that grew with extreme rapidity, and to a size, by
comparison, quite dwarfing that of the original
parent stock.
These fast-growing descendants of the New
Zealand plant had not only the desirable qualities
of texture and flavor of leaf stalk already referred
to, but they retained and advanced upon the
tendency of their ancestors to grow constantly
throughout the year. This anomalous tendency,
[176]
Giant Rhubarb and Crimson Rhubarb
The original winter rhubarb had a stalk no larger than a
lead pencil. By selective breedins Mr. Burbank improved the
plant until it was of marketable size, while retaining the quality of winter
bearing that was about the only merit of the original. S
sequently Mr. Burbank developed descendants of this
original stock that were oj gigantic size, excelling
his original winter rhubarb somewhat
as that excelled its New Zealand
ancestor. The contrast is
shown in this picture.
LUTHER BURBANK
rather than the improvement in the other qualities
of the plant, is obviously the one that requires
explanation. Remarkable improvement in size
and in other desired qualities through selection,
is a more or less familiar method of plant devel-
opment.
But the production of a race of pieplant that
departs radically from the most pronounced and
characteristic trait of the rhubarb family, namely
brief period of bearing, is something that requires
explanation.
A clue to the explanation is found when we
recall that the plants were sent me from a region
lying on the other side of the equator. The plants
were exceptional even there in that they had
shown a tendency to bear — that is to say to pro-
duce juicy leaf-stalks — during the cold season.
Through some unexplained freak of heredity or
unheralded selective breeding, they had developed
a hardiness that had enabled them to put forth
their leaves much earlier than is customary with
all other races of rhubarb.
The difference was only a matter of weeks, and
was of no greater significance, perhaps, than the
observed difference in time of bearing between
different varieties of other vegetables and fruits.
Everyone knows that there are early and late-
bearing varieties of most commonly cultivated
[178]
THE WINTER RHUBARB
vegetables and fruits — summer apples and winter
apples furnish a familiar illustration.
Perhaps someone had discovered a root of
rhubarb that chanced to have peculiar qualities
of hardiness, and had propagated it until he had
a variety that began bearing while the relatively
mild New Zealand winter was still in progress.
But this is only the beginning of the story. The
sequel appears when we reflect that the season
that constitutes winter in New Zealand is coinci-
dent with the summer time of the Northern
Hemisphere.
So when we say that the crimson rhubarb was
productive during the winter in its original home,
this is equivalent to saying that it had the habit of
bearing during our summer time. Transplanted
to California, the New Zealand product continued
to put forth its stalks, quite in accordance with its
hereditary traditions, during what, according to
its ancestral calendar, was the winter season,
although the climatic conditions that now sur-
rounded it were those of summer.
THE INFLUENCE OF ENVIRONMENT
But meantime this plant, like every other living
organism, was of course subject to the directly
stimulative influence of its environment. Its
hereditary traditions had developed what we may
speak of as an instinctive tendency to grow at a
[179]
LUTHER BURBANK
given time of year regardless of climatic condi-
tions; but they had also given it an equally
powerful tendency to respond to the stimulus of
cold weather, and to become productive not
merely in the season of winter but under the
climatic conditions of winter.
In other words, the combined influences of
heredity and of immediate environment were here
as always influential in determining the condi-
tions of plant growth.
But, whereas in New Zealand the environment
of winter — characterized by cold temperature-
coincided with the calendar months of June, July,
and August, in the new environment of Cali-
fornia the conditions of winter were shifted to
the calendar months of December, January, and
February. So the two instincts, one calling for
productivity in June, July and August, and the
other for productivity during cold weather, were
now no longer coincident, but made themselves
manifest at widely separated seasons, thus pro-
ducing a perpetual rhubarb.
So the net result was that, merely through the
retention of old instinctive habits under the trans-
formed conditions imposed by migration to the
Northern Hemisphere, the winter-bearing rhubarb
of New Zealand was transformed, by most careful
and persistent selection, into a summer- and
[180]
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§
LUTHER BURBANK
winter-bearing plant in California. And inas-
much as there are no sharp lines of demarcation
as to just when the pieplant begins and ends
bearing, the two seasons tended to merge, with the
practical result that some of these plants became
all-the-year bearers.
THE POWER OF HABIT
Possibly the use of the words habit and instinct
as applied to a plant requires a few words of
elucidation.
We ordinarily take the habits of a given plant
so much as a matter of course that we are prone,
perhaps, to overlook their close correspondence
with the habits of birds and animals and other
animate creatures. Yet a moment's considera-
tion will make it clear that we may with full
propriety speak of the fixed or regular "habits" of
plants, and that there is no logical reason why we
should not speak of them as being determined
by "instinct," which after all suggests only the
spontaneous response to environing conditions,
present or reflected through heredity.
And the force of the various instincts or habits,
in the case of the plant, as in the case of birds and
animals, is overwhelmingly powerful and quite
beyond the possibility of change in any given
generation.
To cite a single illustration from the case in
[182]
THE WINTER RHUBARB
hand, every gardener knows that he cannot by
any process of cultivation make the ordinary
rhubarb plant change its fixed habit of spring
production. No amount of coaxing and no man-
ner of soil cultivation or fertilization can take
from the rhubarb the impelling force of the
hereditary tendency to put forth its stalks in the
spring time rather than in summer or fall or
winter.
And a similar fixity of habit characterizes in
greater or less measure, most other familiar culti-
vated plants. Artificial selection has extended
the season in certain cases, and early or late-
bearing varieties have been developed as already
noted; but for each variety the habit of producing
at a given time of year is one of the most fixed
and — as regards any given generation — unalter-
able of tendencies.
Recalling this it will not seem strange that the
Australian winter rhubarb retains its habit of
winter production notwithstanding the fact that
it had been transplanted to a hemisphere where
the climatic conditions of its winter were dia-
metrically changed.
ILLUSTRATIONS FROM BIRDLAND
Perhaps the all-importance of this inherent
tendency to gauge habits in accordance with the
calendar will be more clearly apprehended if we
[183]
LUTHER BURBANK
cite an illustration from another branch of the
organic world.
Take the migrations of birds as a familiar
instance. If you watch the birds at all, you have
doubtless noted that the migrants that come to
temperate regions from the tropics arrive each
spring in your neighborhood at a date that you
may fix in advance with almost entire certainty.
The hardier birds, to be sure, such as the robin,
the blue-bird, and the meadow-lark, retire before
the blasts of winter somewhat unwillingly and
they begin their northward migration at a period
that may vary by a good many days or even weeks
according to the forwardness or backwardness of
the season. But the coterie of tender birds —
orioles, vireos, wood-robins, tanagers, fly-catchers
—which spend the winter in the region of the
equator, must begin their northward migration
without regard to the climatic conditions, inas-
much as their winter home is a region of per-
petual summer.
They start northward merely in obedience to
an instinctive time-sense that has been implanted
through long generations of heredity, and they
move across the zones with such scheduled regu-
larity as to reach any given latitude almost on a
fixed day year after year.
In Massachusetts or New York or in Ohio or
[184]
II !'
LUTHER BURBANK
in Iowa, for example, you will find the last flight
of migratory birds, comprising the various species
of wood-warblers and vireos, the orioles, and the
scarlet tanager, making their appearance between
the tenth and fifteenth of May each year, quite
without regard to the advancement of the season.
And a few months later you will note, if you
are observant, that these and the other migrants
disappear in the fall, having taken up their return
voyage at about the same calendar period year
after year, although in one season the September
days may be as hot as August and in another
season they may have the chill of November.
Countless generations of heredity have fixed
in the mechanism of the bird's mind the instinct
that impels it to migrate at a fixed season; and no
transient or variable conditions of the immediate
environment can alter that instinct, even though,
in a given case, its alteration might be vastly to
the advantage of the individual.
EVEN UNTO DEATH
As proving the latter point, and as further
illustrating the force of the instinctive time-sense
under consideration, let me recall the case of the
martins to which reference was made in an earlier
chapter — the case in which these birds starved to
death because in a particular season drought pre-
vented the hatching out of their insect food.
[186]
THE WINTER RHUBARB
Everyone knows that the martin is a bird of
very swift and powerful flight. Its estimated
speed is more than a mile a minute, and it habit-
ually remains hour after hour on the wing. It
was easily within the capacity of the martins that
starved to death in New England to have shifted
their location at the rate of something like two or
three thousand miles a day.
And assuredly within half that distance, prob-
ably within two or three hundred miles at the
most, they would have found an abundant supply
of food.
Now the season at which the martins actually
starved was August; only a few weeks, therefore,
before the time of their regular autumnal migra-
tion. Had the birds lived another month they
would instinctively have begun a long journey to
the south, and a single night's flight would have
brought them to regions where no doubt their
food needs would have been abundantly supplied.
From a human standpoint, it would seem only
natural that the birds, deprived of food, should
have begun their seasonal migration a few weeks
before the usual time; whereby their lives would
have been saved.
Whoever understands the force of hereditary
instinct will realize that such a departure as this
was for the birds impossible.
[187]
LUTHER BURBANK
The instinct of migration comes to the martins
in September, not in August, or at least not in
early August. The habit of migration is no more
determined by any conscious judgment of the bird
than is the habit of spring growth determined by
a conscious judgment of the rhubarb.
The force of untold generations of ancestors
impelled the martins to remain where they were,
even though starvation was the penalty.
Wings they had, with which they might have
sought and found a new environment where food
was plentiful; but they were powerless to use
the wings at this particular season, because the
particular week had not arrived at which the
hereditary clockwork of their organisms would
strike the hour for migration. Taken by and
large, it is better for the race of martins that
they should not migrate until September; this
fact had been established through the test of
thousands of generations, and the result was
registered indelibly in the organism of every bird.
Were it possible to destroy the racial tradition
in the interests of any single generation, the life-
habits of the species would become so variable
and desultory that racial continuity would be
endangered.
So the individuals of a generation throughout
a large region were sacrificed to a racial instinct
[188]
LUTHER BURBANK
which in the main was beneficial to the species.
It will be clear, I trust, how this illustration bears
directly on the case of our winter rhubarb.
RESTORING SUBMERGED INSTINCTS
It could make no difference to the roots of this
plant that they had been unwittingly transplanted
from a land where winter comes in July to a land
where that month betokens summer. The instinct
of bearing at that particular season had all the
force of the instinct that impels the bird to
migrate at a given time; and this instinct could
by no chance be repressed in a given generation,
any more than the martins could make over their
migratory instinct to fit a transitory condition.
But all this leaves quite unexplained the other
fact, which bore so important a part in our story,
that the New Zealand rhubarb when transplanted
to California assumed a new habit of bearing
during the cold season of the Northern Hemis-
phere which corresponded to the summer of its
original habitat and therefore to a calendar period
at which its immediate ancestors had been accus-
tomed to assume a condition of dormancy.
How is our theme of the power of instinctive
habit to be made to coincide with this seemingly
illogical departure?
Our answer is found, as it has been found
in the explanation of other anomalies of plant
[190]
THE WINTER RHUBARB
development, in an appeal from the immediate
ancestry of the rhubarb to the countless galaxies
of its vastly remote ancestry. We have already
pointed out that all plant life traces back its origin,
if you go far enough, to the luxuriant tropical
vegetation of the Carboniferous Era.
But in the case of the rhubarb it is not
necessary to go back so far as this to find an
ancestry habituated to tropical conditions.
In point of fact the rhubarb is, in all prob-
ability, a tropical plant that has but recently
migrated to temperate zones — using the word
recently in the rather wide sense necessary when
we are dealing with questions of racial develop-
ment under natural conditions. In other words,
it is perhaps only a matter of a few hundred
generations since all the ancestors of the existing
rhubarb tribes were growing in the tropics, and
hence, like tropical plants in general, were all-
the-year bearers.
In more recent generations, this habit of per-
petual bearing has been modified, in case of the
rhubarb as in case of nearly all plants of tem-
perate zones, to meet the altered conditions of a
climate in which summer and winter alternate.
To adapt themselves to this change of climate,
plants were obliged to go into retirement in the
winter season, and natural selection preserved
[191]
LUTHER BURBANK
only the races that showed this adaptability of
habit. Thus the common race of spring-bearing
rhubarb, as we know it, was developed.
But the latent capacity to bear at all seasons—
to live a fully rounded life throughout the
year — which may be considered the normal and
inherent propensity of all living things, and which
is observed to be the habit of tropical plants in
general, was never altogether lost. Submerged
generation after generation and century after
century, the hereditary factors that make for per-
petual growth were still preserved, capable, under
changed conditions, of being resuscitated and of
making their influence manifest.
The changed conditions came, in case of the
rhubarb, when the plant found itself in the new
environment of California.
New soil, new atmosphere, new climate — all
these are stimulative. Then successive gener-
ations of the plants were bred from seeds, and
we have already seen that the mixture of strains
thus effected tends to have a disturbing influence
on the germ plasm, permitting new combinations
of characters and resulting in the development of
new forms.
We saw this in the case of the Shasta daisy
and very notably in the case of the hybrid wal-
nuts. We shall note the same thing again and
[192]
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LUTHER BURBANK
again in connection with a multitude of other
plants.
In the case of the rhubarb, the response was
almost immediate. Artificial selection enabled
the plants that manifested the atavistic tendency
in largest measure, to propagate their kind.
And thus, in the course of a few generations
—though not without making selection among
hundreds of thousands of individuals — I was
enabled to assist the plant to bring to the surface
the long submerged tendencies that impelled it
to grow fast, to grow large, and to grow per-
petually.
No NEW PRINCIPLE INVOLVED
And thus the crimson winter rhubarb as it
finally came to perfection in my gardens is
accounted for. In developing it, no new principle
was invoked, no new method even. I merely
took advantage of opportunities afforded by the
translation of the plant from one hemisphere to
another, and aided the plant in putting forth
potentialities that had Jong been repressed but
which still stubbornly persisted as latent factors
or submerged tendencies in the racial germ-
plasm.
Perhaps the matter seems rather complex as
thus explained; and indeed all matters pertaining
to living organisms are complex in the last
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LUTHER BURBANK
analysis. But the methods of operation were in
practice simple.
Granted certain conditions and certain hered-
itary tendencies; granted, in other words, the
materials with which to work, it required only
clear-eyed selection and patient waiting — the
encouragement of some tendencies in the right
direction and the suppression of other tendencies
in the wrong direction — to produce the desired
result.
PROPAGATING THE WINTER RHUBARB
To make the story complete, however, it
should be recorded that, although the winter
rhubarb was developed by mere selective breed-
ing of a pure strain, yet the experiment was not
carried forward without numerous tests of the
hybridizing method.
From the outset the New Zealand plant was
crossed with the native rhubarb, hoping thus to
stimulate variability.
And, almost needless to say, variability was
stimulated. The hybrid plants took on sundry
forms and diverse habits. But it chanced that no
one of these forms was an improvement on those
that were secured by selection from the pure New
Zealand stock.
Nor did this New Zealand stock, even when
developed into my new all-the-year bearer, prove
[196]
THE WINTER RHUBARB
capable of sure propagation from the seed. It
can readily be propagated by dividing the roots
or by cutting out little sections of the root con-
taining a bud, so there is small necessity of
development from the seed. But in this case, as
with so many other cultivated plants, it is essential
to use this method of propagation if we wish to
have an absolutely fixed variety.
An obvious explanation would be that the
original New Zealand rhubarb was of mixed
racial strains. This, indeed, would account for its
tendency to vary, and contribute to its successful
development in California. The inter-breeding
which produced the winter-bearing strain, may
have been done quite by accident in New Zealand,
the plants that came to me embodying the full
possibilities of development without further
hybridizing.
PERPETUAL BEARING Now FIXED
It should be added, however, that even when
grown from seed, the new winter rhubarb always
manifests the tendency to perpetual bearing. This
one trait is fixed, though some of the other
qualities of the plant are still variable.
Using the new terminology we may say that
the tendency to winter-bearing is a unit character
that is latent or recessive, and that the winter
rhubarb has no factors of the opposite trait of
[197]
THE WINTER RHUBARB
limited bearing and therefore cannot revert so
long as it is in-bred. When crossed with the
spring-bearing race, however, the offspring some-
times revert to the old habit, as might be expected.
As already noted, nothing is gained by such
crossing. Nor is there any necessity for the
growth even of pure-bred seedlings. Propagation
by root-division answers every purpose, and, thus
multiplied, the new crimson winter rhubarb, in
its perfected varieties, constitutes a fixed race and
is a permanent acquisition to the list of garden
vegetables.
— It required only clear-
eyed selection and patient
watching — the encourage-
ment of tendencies in
the right direction and
the suppression of tenden-
cies in the wrong direction
— to produce the result.
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THE BURBANK CHERRY
THE EXPLANATION OF A
DOUBLE IMPROVEMENT
HOW MANY assistants have you in your
orchard?" a visitor asked me.
And when I replied, "About a hundred
thousand this morning, I fancy," my visitor
looked quickly this way and that across my
eighteen acre Sebastopol farm, and then seemed
politely incredulous.
"I don't see quite so many," he remarked. "In
fact I can see but eight."
"No," I said, "you don't see them; but you can
hear them if you listen. They are mostly up there
among the cherry blossoms. Notice how their
wings hum as they go from flower to flower."
"You mean the bees?"
"Just so; the bees — they are my most impor-
tant helpers at this season. I should get no cherry
crop without them, and for that matter no plum
crop, no apple crop, and very few flower seeds.
[VOLUME II — CHAPTER VII]
LUTHER BURBANK
In fact, most of us who grow fruit would soon go
out of business, or reduce our farms from acres to
square feet, if it were not for the bee helpers
buzzing about from blossom to blossom."
"But do you depend entirely upon the bees
to pollenize your cherries?" my questioner con-
tinued.
"Not altogether. I am obliged to do some
pollenizing, particularly at the beginning of an
experiment, to make sure of the exact cross that
I desire. But after the experiment is under way,
I for the most part leave the work to the bees.
They operate, as you see, on a large scale, making
a thousand pollenizing experiments where I could
make one. And in the end the results of their
work are highly satisfactory."
HOW POLLENIZATION Is EFFECTED
To illustrate the necessity for the aid of the
insect helpers, I usually show the method by
which cross pollenizing is effected when done by
human hands.
I select a blossom that is almost mature but
has not opened, and cut it across with a very
thin, sharp knife, taking the petals about half way
down, thus amputating all the stamens, but
leaving the pistil.
Pollen which has previously been collected
upon a watch crystal from some open flowers is
[202]
Ready /or Pollenation
A detached cherry blossom in which the pollen-bearers are
mature. The pollen may be shaken into a watch crystal for
Juture use or it may be applied directly to the head of a flower prepared
in the way shown on page 200. The object, of course, is to bring
the pollen of one flower to the pistil of another. The bees
aid constantly in accomplishing the same purpose.
LUTHER BURBANK
applied by lightly touching the finger to it, then to
the stigma, taking care to cover the top of the
stigma completely with the pollen.
This is a simple enough procedure, but it must
be done carefully, as the number of tests that one
experimenter can manage is limited.
Moreover, it is necessary, of course, in a case
that calls for hand pollenizing, to mark the blos-
som with a tag of some sort, else there would be
no record of the experiment, and no way of telling
whether it finally proved successful. Again, it is
usually desirable to remove other blossoms from
the cluster in which the artificially pollenized one
grows, to give a better opportunity for develop-
ment of this individual.
If, finally, we are to make absolutely certain
that no other pollen comes in contact with the
stigma, thus guarding against the possibility of
fertilization of the flower by other pollen than
that intended, it may be desirable to tie a paper
bag over the flower.
The latter procedure is not usually necessary,
particularly if care has been taken to cover the
stigma with pollen, as once this is done there is
almost no danger that any foreign pollen will find
lodgment. Moreover, the flower from which the
petals have been cut, as just described, will not
attract the bees, and would probably not be fer-
[204]
Seeking Aid oj the Bee
The method of pollenizing on a large scale sometimes
employed by Mr. Burbank is to place a branch oj wild cherry
blossoms* as shown in this picture, on a cultivated tree. The bees will
then effect cross-pollenation* and the virile qualities of the wild
cherry will be introduced into the strains of the cultivated
ones. As in the case oj the hybrid plums, the off-
spring of later generations may manifest
the good traits of both ancestral
strains in combination.
LUTHER BURBANK
tilized at all if our experimental pollenization
should fail.
TIME THE LIMITING FACTOR
But even when restricted to the essentials, the
process takes time; and although some thousands
of hand-pollenations are done annually in my
gardens and orchard, yet, as intimated, we try
to leave the bulk of this work to the bees. Of
course, these otherwise admirable helpers make
no distinction between different varieties of blos-
soms, passing freely from one tree to another,
regardless of the variety; but they usually confine
their attentions on any given day to trees of a
single species; that is to say, they do not ordinarily
pass from cherry blossoms to the blossoms of the
plum or almond, even if all are in season. They
seem to prefer not to mix their sweets. So they do
not distribute pollen to the wrong flowers as often
as might be supposed.
Where I wish to make pollenizing experiments
on a larger scale, I sometimes place a branch of
a cherry tree in full bloom among the branches
of the tree of another variety, with which I wish
to effect hybridization. The bees then transfer
the pollen from the borrowed limb to the flowers
on the surrounding branches, and a thoroughly
satisfactory cross pollenation is often thus brought
about.
[206]
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LUTHER BURBANK
If a visitor who observes my cherry trees in
the blossoming time chances to visit my orchards
a little later, at the time of fruiting, he will prob-
ably be disposed to admit that my method of
experiment has had very satisfactory results. For
the cherries that grow on my trees are among the
largest and most luscious, as well as the most
abundant, that have ever been produced.
The visitor will perhaps be surprised to find
many scores of cherries quite different in appear-
ance growing on the same tree. This, however, is
the result of grafting.
Seedlings grown from seed produced on a
single tree may vary widely, but the immediate
fruit of any individual tree is fairly uniform,
unless the tree has been grafted.
But trees on my farm always are grafted, so
the phenomenon of divers varieties of fruit on the
same tree is a familiar one.
AN UNSTABLE RACE
The cherry is at best a variable fruit. Like
most orchard fruits, it cannot be grown depend-
ably from seed. But, of course it is necessary in
producing new varieties to work from seedlings,
and from the standpoint of the experimenter who
wishes to produce new varieties, it is fortunate
that the tendency to vary exists. For, as our other
experiments have taught, in the case of plants
[208]
THE BURBANK CHERRY
already described, it is only when a tendency to
vary from a fixed racial type has been brought
about by hybridization, or otherwise, that the
material is furnished upon which the experi-
menter can build.
In the case of the cherry, all the familiar
varieties are the result of hybridizing experiments
performed either consciously or unconsciously in
the past.
By working with the seed of any existing
variety, one secures plants of numerous types that
suggest different possibilities of development.
THE IDEAL CHERRY
In the course of my experiments, however, I
have had occasion to bring together, through
artificial pollenization, various standard varieties
of the cherry, and, although I have not found it
necessary to send to foreign countries, yet the
stock with which I have worked represents races
which have been developed in regions as widely
separated as Russia, the eastern United States,
California, and Japan.
It has been my aim to combine the desirable
qualities of different races of cherries from these
widely separated regions, and the task here, as
in so many other instances, has chiefly consisted
in persistent selection among multitudes of seed-
lings of widely diverse types.
[209]
I PI
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THE BURBANK CHERRY
The foundation stock with which I chiefly
worked was the variety known as Early Purple
Guigne, crossed with the Black Tartarian; but in
subsequent crosses the qualities of Russian, French
and American cherries and of numerous others
were introduced, in an attempt to achieve the
ideal cherry.
A familiar but notable characteristic of the
cherry, in which it differs markedly from most
other fruits, is its habit of ripening at the very
beginning of summer, while many of the small
fruits are not yet in blossom. This characteristic
gives the cherry peculiar commercial value, as it
comes on the market at a time when there is a
scarcity of fruits.
It occurred to me many years ago that there
would be a still greater advantage if a cherry
could be produced that ripened several weeks
earlier than any variety then on the market.
So early ripening was one of the first ideals
at which I aimed. With that object in view I
naturally selected for my early hybridizing
experiments specimens growing on trees that were
observed to bear earlier, even if by only a few
days, than surrounding trees.
To come at once to the sequel of the story, I
may say that I was able after many years of
experimentation to produce a cherry that ripens
[211]
LUTHER BURBANK
about three weeks earlier than any variety
hitherto grown in California. This result was
achieved by persistent selection, generation after
generation, of specimens that manifested the
early-fruiting propensity. But the full bearing of
the story cannot be understood unless attention is
given to the almost numberless complications that
were involved.
SEEKING MANY ENDS AT ONCE
Had the only object sought been the produc-
tion of a cherry that ripened very early, it would
not have been very difficult to attain success.
In that case all other qualities could have been
disregarded, and attention given solely and exclu-
sively to the question of time of fruitage. The
cherries that ripen earliest each season being
selected, I should presently have produced a race
of early bearers, beyond peradventure. Selection
carried through a comparatively small number of
generations would have sufficed to give me what I
sought.
But a moment's reflection makes it clear that
there would be no commercial value in a cherry
that ripened earlier than its fellows, unless this
cherry combined with the quality of early
ripening other qualities of size and abundance and
fitness for shipping, that give the cherry its value
as a market fruit. It is obvious that in selecting
[212]
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LUTHER BURBANK
my cherries it was constantly necessary to bear in
mind not merely one quality but several qualities,
and it requires no great knowledge of plant exper-
imentation to see that this greatly complicated my
problem.
DIVERSIFIED QUALITIES REQUIRED
In point of fact, the qualities that are required
in a really satisfactory commercial fruit are much
more diversified than the ordinary observer would
ever suspect.
In the case of the cherry there are at least
a dozen quite distinct qualities, which might be
spoken of as unit characters, that must constantly
be borne in mind.
A cherry that will bring a good price in the
market must be large in size; it must be attractive
in color; it must be sweet and savory to the taste;
and it is of prime importance, particularly from
the California standpoint, that the fruit shall be
of such texture and quality of skin as to bear
shipment across the continent, and so reach the
Eastern market in good condition.
As much as this will be obvious to every eater
of "cherries.
But from the standpoint of the fruit grower,
there are many other qualities that are no
less important. It is necessary that the tree that
bears the cherries shall be hardy and able to with-
[214]
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LUTHER BURBANK
stand the frosts; that it shall have the quality of
vitality that makes it immune to the attacks of
insects; that it shall have abundant foliage to
protect the fruit from the sun; and that it shall be
a prolific bearer no less than a bearer of fruit of
marketable quality.
All this, in addition to the quality of earliness
of bearing to which reference has already been
made.
If we add that there are certain minor quali-
ties, to be borne in mind, such as the question of
length of stem, number of cherries to the cluster,
and tendency of the fruit to cling to the stone in
one case or leave it readily in another, an inkling
will be gained of the complications of the problem
in heredity that confronts the developer of an
improved race of cherries.
But the full significance of these complications
can scarcely be appreciated wholly by any one
who has not been confronted by them in actual
practice.
If I have been able to overcome them in a
relatively brief number of years, it is because I
have worked persistently, selected with discrimi-
nation, and invoked the aid of the bees in making
experiments on a large scale.
The modern student of heredity, in dealing
with cases such as this, is able to give a somewhat
[216]
The Earliest Cherry
By Jurther experiments in selective breeding, Mr. Bur-
bank has developed a cherry that is even earlier than the one that
bears his name. This new cherry is of handsome form and color and a
profuse bearer, as the illustration shows. There is, of course, a limit
to the development oj the habit oj early bearing, but what this limit
is can be determined only by long series of experiments in
selective breeding. Mr. Burbank is constantly on the
lookout for individual fruits that show peculiar
qualities, and these are carefully preserved
as material for further experiments.
LUTHER BURBANK
tangible illustration of the difficulties involved
with the aid of simple mathematics. He does this
on the basis of the Mendelian interpretation of
the method of transmission of unit characters of
which we have learned something in an earlier
chapter.
THE COMPLICATIONS ILLUSTRATED
It will be recalled that we had occasion to
consider such opposing traits as blackness and
whiteness in our white blackberry, large size and
dwarf size in the case of our walnut trees, stone
fruit versus stoneless fruit in cases of our plums,
and perfume versus lack of perfume in cases of
the calla, as pairs of unit characters that are
mutually exclusive in case of any individual, but
which both tend to recur in the second generation
of hybrid offspring.
It will be recalled, too, that a specific illustra-
tion of the formula according to which such
recurrence takes place, was found in Professor
Castle's experiments in crossing a black guinea
pig with a white one; in which case, although all
the offspring were black, the quality of whiteness
reappeared in one-fourth of the descendants of
the second filial generation.
Now it should be observed that this ratio of
one in four is a ratio that has been found to hold
good in a very great number of experiments
[218]
A Yearling Cherry
This picture shows the remarkable qualities of form and
foliage of a typical Burbank cherry tree one year old. Mr. Bur-
bank selects his seedlings always with an eye to many qualities of form
and vigor of growth* and color of leaf, that the less practiced plant
developer might overlook. He also eliminates any plants
that show susceptibility to mildew or other fungus
diseases. Hence his orchards are made up
of trees that are relatively immune
to disease and that do not
need to be sprayed.
LUTHER BURBANK
applied to various races of animals and plants,
when a cross has been made and a record kept of
the results with reference to a single pair of unit
characters, such as blackness versus whiteness in
the case of the guinea pigs. In such a case, where
the offspring of the second filial generation are
interbred, it has been clearly demonstrated, that
on the average, one-fourth of the offspring
of the second filial generation will resemble the
paternal grandparent, and one-fourth the mater-
nal grandparent; the remaining half being of
mixed heredity.
Stated otherwise, there is an even chance that
in any group of four offspring of the second filial
generation, one individual will resemble each
grandparent as regards a given unit character.
Applying this rule to the case of our cherries,
and considering for the moment only the matter
of early-bearing versus late-bearing, it should
result, if these qualities constitute a pair of unit
characters, that by crossing an early-fruiting
cherry with a late-fruiting one, the descendants of
the second generation would show one specimen
in four growing early fruit, one in four growing
late fruit, and two of intermediate tendencies.
All that would then be required would be to
breed exclusively from the one-fourth that were
early-bearers, destroying the three-fourths that
[220]
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LUTHER BURBANK
lacked this quality or had it mixed with the unde-
sirable quality.
NOT So SIMPLE IN ACTUAL WORK
But, unfortunately, the simplicity of the
formula vanishes as soon as we come to consider
a second, and third, and fourth pair of unit
characters.
Here also the formula has been worked out
in mathematical terms; and it appears that when
several characters are involved, we at once come
to deal with numbers that are no longer easy
to keep track of. Moreover, the various pairs
of unit characters may be juggled in an almost
infinite variety of ways.
We are seeking, for example, (1) an early-
bearing cherry of (2) good size, (3) fine color,
(4) sweet taste, and (5) good keeping quality.
Suppose, for the sake of argument, we consider
each of these to constitute, as contrasted with the
opposite condition, one member of a pair of unit
characters.
Then it appears that, according to the theory
of chances which underlies the interpretation of
the Mendelian formula, the probability that any
given combination of these five qualities will
appear in an individual specimen of the progeny
of the hybrid generation is only one in about five
hundred.
The Improved Giant
These are the improved descendants of the black cherry
shown on page 221. They represent perhaps the finest cherry
ever developed up to the present time, although still finer ones will doubt-
less appear in Mr. Burbank's cherry colony in succeeding years. All
the cherries in Mr. Burbank*s colony are now of aristocratic
lineage, and new combinations among them are made through
cross-pollenation each season. New seedlings are raised
and grafted into the colony, so there are always dons
on the tree that are not yet in bearing, and each
recurring cherry season brings its surprises.
LUTHER BURBANK
We shall have early-bearers that are of good
size and taste, but lack shipping quality; other
early-bearers that are good shippers but lack size
or taste; yet other specimens that have size and
taste and shipping quality, but lack the quality of
early bearing; and so on throughout all the possi-
ble combinations of five pairs of qualities.
But the combination of all the desired char-
acters in a single individual will take place very
rarely indeed.
And when we advance from five pairs of unit
characters to ten or twelve, as we have already
seen that we must do in the case of our cherry,
the matter becomes almost infinitely complex. As
we increase the number of qualities under consid-
eration, the number of possible combinations
among them increases at an alarming geometrical
ratio.
It appears that whereas there is an even
chance, when only a single pair of qualities was
in question, of producing one offspring like each
parent in each group of four; and whereas there
is the same even chance of producing one off-
spring like each parent in every group of 256
individuals when four pairs of unit characters are
in question — when we have to deal with ten pairs
of unit characters the possible arrangements have
become so bewildering and complex that there is
[224]
A Stalwart Injant
The seedling cherry here shown, putting Jorth its solid
clusters of blossoms while only knee-high, illustrates two or three
of the characteristic qualities of the Burbank orchard fruits — notable the
qualities of early and prolific bearing. Mr. Burbank constantly
selects with these qualities in mind, with the result that his
orchard trees generally bear fruit at afar earlier age
than ordinary ones. This precocious
little sapling is a typical plant in
Mr. Bur bank's gardens.
LUTHER BURBANK
even chance of producing a single offspring like
each grandparent only in each group of more
than a million progeny!
QUANTITY PRODUCTION NECESSARY
Such a computation, as made in accordance
with the Mendelian formula, in itself serves to
supply a ready answer to those Mendelians who
have questioned the necessity of making experi-
ments on the elaborate scale that I have all along
followed out. According to strict Mendelian
reasoning, it is clear that we must deal with
thousands of seedlings in order to stand a chance
of securing a single one that shows a desired
combination of qualities, when six or eight qual-
ities are in question — and I seldom work with
less than twice this number in view.
And the case is even more complex than this
computation would show, because I am always
concerned not merely to combine a half dozen or
a dozen desirable qualities, but to have a wide
range of choice among numerous individuals
showing this combination, that one may be found
which exhibits the desired qualities in the super-
lative degree.
It is fair to assume, then, that I should never
have secured the Burbank Cherry, and following
it my newer varieties of cherries that: (1) fruit
weeks before the usual cherry season, and
[226]
The Abundance Cherry
This shows the actual size and appearance of one oj Mr.
Burbank's newest cherries, called the Abundance. Like the
Giant Black Cherry, it is the product oj crossing between the various
highly developed members of the cherry colony. Mr. Burbank does not
introduce a new fruit unless it is equal to any existing variety in
all its qualities, and superior to any other in at least one
quality. The Abundance Cherry fully meets these
conditions, its pre-eminent quality being its
habit of prolific bearing. In size it is also
notable, as the illustration shows.
LUTHER BURBANK
(2) produce a superabundant crop of fruit of (3)
the largest size, (4) best color, (5) firmest texture,
and (6) finest quality; growing in (7) easily
gathered clusters on (8) trees of fine shape that
are (9) hardy and (10) immune to the attacks of
insects, had I not extended my experiments far
beyond the narrow limits of hand pollenation,
with the aid of my hosts of indispensable helpers,
the bees.
So the biometric computations give fullest sup-
port to the practical methods that I have employed
for the past forty years.
Meantime, the results of my experiments-
proving the possibility of segregation and reas-
sembly of these diverse qualities — give vivid
illustrations of the fundamental truth of the
theory of unit characters, if these be properly
interpreted.
GOOD FRUIT FROM BAD ANCESTORS
As a further illustration in point, note this
curious circumstance:
I have in various instances used as a parental
stock, for purposes of hybridization, a cherry that
produced a totally worthless fruit. The object of
this selection was to introduce into a developing
strain of cherries some good quality — say prolific
bearing — that the otherwise worthless cherry
showed in high degree.
[228]
THE BURBANK CHERRY
The immediate progeny of this cross would be
of no value as the bad qualities of the worthless
cherry were dominant. But among the remoter
descendants I have been able to discover indi-
viduals that combine the quality of prolific
bearing with the good qualities of the other parent
stock, and in which the undesirable qualities of
the original worthless ancestor were quite elim-
inated.
It must be clear that this result could not have
been brought about if the various pairs of qual-
ities— large size versus smalf size, sweetness
versus sourness, prolific versus shy bearing, and
the like — had not been separated in the germ
plasm of the hybrids in such a way that the unit
characters could be sorted out and any good
quality transmitted to the later generations, unim-
paired by its contact with the opposing bad
quality.
In other words, had there been a blending of
traits in the sense in which the older experi-
menters imagined the traits of hybrids to be
blended, we should have had at best a cross in
which the qualities of the worthless cherry were
mingled with those of the valuable one; a race
which, if somewhat better than its worthless
ancestor, was somewhat worse than its valued
one.
[229]
LUTHER BURBANK
And it would never have been possible to breed
out altogether the undesirable qualities that the
original cross had introduced.
SEPARATING THE TRAITS
But we have seen in the case of the cherries,
as we had previously seen in the case of some
other plants, and as we shall have occasion to see
in numberless others in future, that it is possible
to breed traits into a hybrid strain, and then breed
them out again.
In point of fact, no progress in the production
of new varieties could have been made along the
lines of my experiments, were it not for this possi-
bility.
My Shasta daisy, for example, is not inter-
mediate in size between the species from which
it sprang, but larger than any of them. My white
blackberry is not intermediate in color between
the parental strains, but is of a far purer white
than its light colored ancestor. My stoneless plum
is more stoneless than the race from which it
sprang, although that race has been crossed again
and again with strains of plums that invariably
produce a stony seed covering. Some of my hybrid
walnuts are far larger than either parent stock,
and some are far smaller than either.
And so on throughout the list of the hybrid-
izing experiments through which the new races of
[230]
Truly Abundant
This picture shows a branch of Abundance Cherries great-
ly reduced in size. A comparison with the lije-size cherries
shown on page 227 will give a still better idea as to the bulk of fruit on the
branch here shown. Few other qualities of an orchard tree are
more care
ityto
The
sfully considered by Mr. Burbank than the capac-
pear fruit abundantly and bear it every season,
'he Burbank products show these Qualities
products show these qua
in remarkable degree — and
the
Abundance Cherry
the head of the list.
is near
LUTHER BURBANK
plants have been developed at Santa Rosa. Every-
where we find evidence of the segregation of unit
characters and their re-commingling and re-assort-
ment in later generations.
Nowhere else, probably, can there be found
such an aggregate mass of testimony to the opera-
tion of this principle as will be supplied in the
pages that tell of my various experiments in plant
breeding.
We shall have occasion to see that there are
cases in which there is a blending of traits, and
we shall find an explanation of such blending.
But, as the cases already presented sufficiently
illustrate, the carrying forward of characteristics
unblended, and the possibility of their restoration
after long submergence in new combinations, con-
stitutes the underlying principle that makes possi-
ble the rapid development of new forms of plant
life.
And, reverting to the cases in hand, there is
no better illustration of the truth of this proposi-
tion than that furnished by the new cherries which
present in superlative measure, in a single indi-
vidual, ten or a dozen clearly definable qualities
that have been sorted out and brought together
from the commingling of widely divergent ances-
tral strains.
The traits that were developed through
[232]
THE BURBANK CHERRY
response to the environment in widely scattered
geographical territories and through hundreds of
generations, have been brought together, in com-
binations never hitherto presented; with the result
that my early-bearing, large sized, bright colored,
and highly flavored cherries constitute essentially
a new variety of fruit, while at the same time they
evidence with full force the all-compassing influ-
ence of the laws of heredity.
— According to strict Men-
delian reasoning, it is clear
that we must deal with
thousands of seedlings in
order to stand a chance of
securing a single one that
shows a desired combina-
tion of qualities, when six
or eight qualities are in
question — and I seldom
work with less in view.
•a
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•X ^5-C
THE SUGAR PRUNE
How A TREE WAS CHANGED
To FIT THE WEATHER
PROBABLY you have heard the story of the
General who declared it impossible to
build a bridge across a certain stream that
obstructed the march of his army until he had
plans and specifications and blue prints for the
work. While he waited for these — so the story
goes — a subordinate built the bridge, and reported
to his superior with the suggestion that it
might be well to march the men across the bridge
forthwith and then make the drawings at leisure
afterwards.
A visitor at my orchard told me this story, and
applied it to the case of some of my newest varie-
ties of plums.
"It appears to me," he said, "that your custom
resembles that of the young soldier who built the
bridge without the plans and specifications. You
appear to have developed a good many of your
[VOLUME II— CHAPTER VIII]
LUTHER BURBANK
fruits on the same principle. You seem to have
gone ahead and produced the fruit, while a more
cautious experimenter would have been occupied
in designing hybridizing methods and testing
unit characters, and would not have been fully
prepared to start on the actual constructive work
until about the time you finished."
Whatever the force of this comparison, it is true
that I have often succeeded in producing a fruit
of the finest quality by methods that to a less
practiced experimenter might look haphazard;
methods that did in point of fact lack something
of the precision that an investigation conducted
solely for purposes of scientific record rather than
for practical results might have required.
Such is the case with a large number of experi-
ments in plum breeding. Here I have dealt with
such vast numbers of individuals and brought into
the hybridizing tests such varied and so many
races, that accurate record of every step of a series
of experiments extending over a term of years was
quite out of the question.
My "Combination" plum has a pedigree, could
it be accurately traced, that includes strains of
almost every race of plums under cultivation.
From the seed of this strange hybrid you may
produce trees that will bear fruit closely similar
in all respects to at least a score of entirely
[236]
The Giant Prune
One of Mr. Embank" s earliest important prunes is here
shown greatly reduced in size. The Giant was introduced in
1893. It has many exceptional qualities* and is particularly prized
as a market plum to be eaten Jresh. As a drying prune
it is surpassed by other oj Mr. Burbank's
more recent developments.
LUTHER BURBANK
different well known varieties or races of plums.
The mixed pedigree of the product is recorded
in this motley galaxy of offspring; but details as
to all the parental crosses, tracing back along an
experimental search of thirty years duration, are
not to be had. The original parents used in the
first cross are of course known; but successive
generations deal with tens of thousands of seed-
lings. So it was impossible for anyone who was
carrying out, as I have been, not less than three
thousand different plant breeding experiments
each year, involving in the aggregate not fewer
than six thousand different species, to trace
accurately, much less to record, each and every
cross-fertilization among the myriad blossoms of
my orchard.
Yet a chance hybridization might by good
fortune effect precisely the needed combination
of qualities to give me a fruit that had eluded my
most earnest efforts at systematic breeding.
Very often, to be sure, I can judge from the
result what the racial strains most probably were
that were blended to produce the new hybrid.
But even this is not always possible, and not a few
among the thousands of new varieties of plums
that have originated in my orchard are of untraced
and untraceable pedigree, at least as regards some
of their strains.
[238]
THE SUGAR PRUNE
When I say that something like seven and a
half million seedlings of the plum have passed
under my hand and eye in the course of my many
series of experiments in the perfection of this
fruit, the reader will not wonder that there are
gaps in the record.
DIFFICULTIES INVOLVED
On the other hand, it must be understood that
there are almost numberless instances in which
the hybridizing of different strains of plums has
been effected by hand, in accordance with the
most rigid scientific methods, and accurately
recorded in my plan books. Indeed, this is true
in almost all cases of the first cross through which
a tendency to variation has been brought about.
The first generation hybrids are usually very
much alike, and inspection of them often gives no
clues to the ultimate results to be expected. But
in the next generation all the divergent character-
istics of both racial strains fight for representation,
and the diversity of forms produced may baffle
accurate description.
Beyond this stage it is usually necessary for
the practical breeder to turn over the task of
cross-fertilization to the bees, contenting himself
with keeping a sharp outlook for seedlings that
show desired combinations of traits.
How diversified these traits may be in case of
[239]
LUTHER BURBANK
a market fruit has been illustrated at some length
in the preceding chapter. In this respect, most
plums are at least as complex as the cherry, and
the requirements in the case of the "perfect"
prune are even more exacting.
The word prune, it should perhaps be
explained, is applied in California to any plum
that can be dried with the stone in place without
fermentation of the pulp. The quality that per-
mits such drying is largely dependent on the
amount of sugar that the fruit contains. There
are prunes and prunes, as even the most
unpracticed observer must know, and there are
gradations of size, flavor, and sugar content that
are vastly important from the standpoint of the
orchardist and by no means without interest from
the standpoint of the consumer.
One of the tasks I early set myself was to
produce a prune that should excel all others in
the qualities, singly and combined, that make for
perfection in this valuable fruit. I think I
may fairly claim to have accomplished that end,
although I shall not pretend that my ideal of a
perfect prune has thus far been quite attained. I
am not sure that I should be over-pleased if it
had been; one does not really wish to reach the
end of a trail, leaving nothing to strive for, no
unknown territory to explore.
[240]
illlSpfil^i?
LUTHER BURBANK
It is a matter of more or less authentic record
that the prune was originally introduced into
California by a French sailor named Louis Pellier,
who came to San Francisco in 1849 with the first
horde of gold seekers.
PRUNES FROM FRANCE
Failing to make his fortune in the mines, this
young man, in association with his brother who
had presently joined him, established a nursery
and conducted it with a certain measure of
success until 1856 when one of the brothers
returned to France to bring back a bride. He
brought also some prune cuttings. And these,
notwithstanding the long journey by way of the
Isthmus, were still alive when California was
reached.
They were immediately grafted upon plum
stock, with entire success.
The most important of the varieties of prune
thus introduced was the common French prune,
sometimes known as the prune d'Agen. The
descendants of this stock made up the large prune
orchards of California for the ensuing half
century.
The French prune, while not without its good
points, is by no means a perfect fruit It is a
cling-stone, which is a serious defect in a prune.
Moreover, the stone itself is rather large in pro-
[242]
THE SUGAR PRUNE
portion to the flesh. The fruit ripens too late to
be profitable in some parts of the country, and
the risk of having the crop destroyed by the early
rains is a serious defect everywhere. Neither is
the tree a strong grower, or a very reliable pro-
ducer, or of the most symmetrical growth.
It occurred to me, therefore, when I first
took the matter in hand, that among the essential
qualifications of the ideal prune at which I must
aim would be early ripening and the production
of a larger, still sweeter free-stone fruit that would
be borne in profusion.
THE IDEAL PRUNE
We have had occasion to point out that the
common orchard fruits do not breed true when
grown from the seed. Explanations of this fact
have been given, and fuller explanations will
appear in subsequent chapters.
Here it suffices to note that the prune is no
exception to the rule.
Very seldom does the seed of a prune tree
produce a fruit that much resembles the prune.
Usually the fruits are of all sizes, shapes and
colors. They are sweet, sour, bitter, as the case
may be. Some of them crack and others remain
smooth. The trees on which they grow are many
of them ill-shaped, weakly, or subject to disease.
Although the parent form may have been an early
[243]
THE SUGAR PRUNE
ripener, the seedling may produce fruit that
ripens so late as to be useless.
All of which serves to give an inkling of the
difficulties that beset the plant experimenter who
sets out in pursuit of an ideal prune.
Moreover, the variety of characteristics re-
quired to make up the ideal prune is far greater
than the novice might suppose. It is a matter of
course that the fruit should be large and well
flavored — though not too large, lest it become too
difficult to dry; and that it should be produced
in abundance.
But there are various equally essential points
that the novice might overlook.
There is, for example, the matter of quality of
skin, determining the fitness of the fruit to undergo
the lye bath which is an essential part of prune
curing.
It is necessary to dip the prunes in this bath,
consisting of a solution of potash or lye, in order
that the skin may crack in such a way as to permit
the rapid evaporation essential to quick drying.
But in a very large number of cases, prunes
that have every other essential quality fail when
subjected to this final test. It is not too much
to say that I have developed hundreds of new
varieties of prunes that were well nigh perfect as
to quality, but which had no commercial value
[245]
LUTHER BURBANK
whatever because they failed to stand the acid —
or to be literal the alkali — test.
So the experimenter is always confronted with
the possibility of failure at the very last, even
when his efforts seem to have met with complete
success at the earlier stages. With the utmost
solicitude, therefore, he must watch the fruit as it
passes through the potash bath.
If the skin peels from the fruit instead of
cracking, that particular variety is worthless, no
matter what its other good qualities.
Moreover, the cracks in the skin must be very
small and numerous. If they are too far apart
by the hundredth of an inch the prune will have
a rough appearance that mars it from the com-
mercial standpoint. If the skin is too thin, so that
in gathering and handling the fruit is bruised, it
can never make a commercial prune. But on the
other hand, the skin must not be too thick as then
it would not be properly cut by the lye. In a
word, there must be the most nicely balanced
qualities of the skin of the fruit, and without this
final touch, the prune is a failure, even though it
grows to seeming perfection on the tree.
The intrinsic qualities, in addition to perfection
of skin, that I aimed at from the outset, were large
size, increased production of sugar, and early
ripening.
[246]
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LUTHER BURBANK
The matter of size is doubly important because
this largely determines the price that a prune
brings in the market. The sugar content is
obviously important because upon this chiefly
depends the drying quality of the fruit. And the
matter of early ripening is at least as essential as
any other quality, because the prune is dried in
the sun, and the fruit that ripens late in the season
not only often lacks sunshine to complete the
process, but may be absolutely ruined by the rains
Which begin to fall in the early autumn.
How I ACHIEVED SUCCESS
When I began my quest of a perfect prune, in
the year 1879, it at once occurred to me that
something might be accomplished by hybridizing
the French prune with another variety known as
the English Pond's seedling but usually called in
California the Hungarian prune. This was a large
and handsome fruit, while the French prune
brought to the combination the qualities of rich
flavor and relatively high sugar production. If
these diverse qualities could be combined in a
single fruit, I saw that a great advance would
be made.
The little French prune was selected as the
mother tree and many thousand blossoms were
hand pollenated from the Hungarian.
The offspring of this cross were as variable as
[248]
THE SUGAR PRUNE
had been expected, and among the seedlings were
some that produced fruit of superior quality.
Four years later, at the meeting of the California
State Horticultural Society, I had the pleasure of
exhibiting no fewer than seventy varieties of these
crossbred seedlings. And in 1893 two new plums
were introduced as representing the best selection
among the almost myriad forms of the hybrid
progeny.
One of these new plums was named the Giant,
the other the Splendor.
The former is a handsome plum practically
intermediate in qualities between the original
parents. It has peculiar value as a shipping plum,
and in particular it gained popularity with the
canners because its skin has the property of rolling
away from the fruit when placed in boiling water,
leaving the rich, honey-colored flesh. But these,
of course, are not the qualities desired in the
prune.
The other variety, named the Splendor, is
about one-third larger than the common French
prune and contains something like five per cent,
more sugar; its quality and flavor are also
superior. It has, moreover, the drying qualities
of the prune, and it was freely predicted by
many who knew it that it would soon completely
displace its French progenitor.
[249]
THE SUGAR PRUNE
But unfortunately it had one single peculiarity
that placed it at a disadvantage; namely, the
propensity of the fruit to cling to the tree when
ripe.
It dries into a first class sweet prune, but it
dries on the tree, and that is an insuperable defect,
because the prune grower demands that the fruit
shall fall naturally to the ground. He does not
wish to be obliged to take the trouble even to
shake the tree.
So the unfortunate propensity of the new
prune to hold to its moorings, so to speak, greatly
marred its value.
AT LAST, A SUPERLATIVE PRUNE
In the year 1899, however, after almost twenty
years of continuous and laborious effort, I was
finally able to present a prune which met the
expectations of the most sanguine; a prune which
combined all the good qualities of its progenitors
and combined them in superlative degree, and
which, in addition, had the peculiarly desirable
quality of ripening about the first of August, three
or four weeks in advance of the usual period of
the prune harvest.
This almost perfect prune was placed on the
market in 1899 under the name of the Sugar
Prune.
A description of the new fruit was given by
[251]
LUTHER BURBAXK
Mr. B. M. LeLong, sccrotaiy of the California
State Board of Horticulture, as follows :
"The sugar prune is an extremely early prune,
ripening August 1st: it grows superbly with yellow
flesh, tender, and rich in sugar. The skin is very
delicate, at first of a light purple tinted with green,
changing at maturity to dark purple, covered with
a thick white hloom. The form is ovoid, slightly
flattened, measuring five by six and a half inches
in circumference, average size fifteen to a pound,
which is two or three times larger than the French
prune; the fruit stock is short, and severs very
easily from the stem as the fruit reaches maturity;
the pit is of medium size, flattened, slightly
wrinkled and most often separated from the flesh;
the skin is so thin or porous that the fruit begins
to shrink on the tree as soon as ripe."
To add to the value of the sugar prune, the
tree on which it grows is unusually vigorous and
very productive.
Analysis of the fresh fruit at the State Univer-
sity discloses the fact that it is nearly one-fourth
sugar — the exact amount being 23.92 per cent,
contrasted with the 18.53 per cent, sugar content
of the French prune, and the 15.33 per cent, of
prunes in general.
Not only does the sugar prune contain far more
sugar than any of the varieties from which it
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LUTHER BURBANK
sprang, but it fully equals the French prune in
flavor, and it is two to three times as large. It is
far more productive, and can be grown for one-
third to one-half the cost of producing the French
prune. In flavor it is fully equal to the celebrated
Imperial, and, in most striking contrast to that
fruit, it is exceedingly productive.
Add that the new prune excels all other
varieties in the extreme earliness of its time of
fruiting, and it will be obvious that the sugar
prune marks at least a long step towards the ideal
at which I aimed. It ripens at a time when the
weather is hot and dry, so that it can be rapidly
cured. A month or so later when the other
varieties are maturing, the weather is often foggy
and cloudy and sometimes even rainy, so that fruit
curing is carried on under difficulties and often
with serious loss.
It is not strange, then, that the sugar prune met
with an immediate and enthusiastic welcome from
many fruit growers, although of course there were
regions in which a prejudice was shown against it,
such as always meets any new product.
In the markets of the East, the demand for the
sugar prune was soon far in excess of the supply.
A WONDERFUL LABORATORY
We have seen that the essential quality of the
prune, and that which differentiates it from plums
[254]
THE SUGAR PRUNE
in general, is its inherent tendency to produce a
large percentage of sugar.
A great number of fruits share with the prune
the capacity to manufacture sugar, but few other
fruits have the power in such supreme degree.
The manufacture of sugar by fruits is so familiar
a phenomenon that we usually take it for granted
and give it no thought. Yet a moment's consid-
eration makes it clear that this capacity is one of
the most extraordinary functions in the whole list
of vital phenomena.
Holding a ripe prune in my hand I am some-
times led to reflect that this is in many ways the
most remarkable of chemical laboratories.
Within the cellular structure of this fruit, a
combination and metamorphosis of chemical
products is brought about that the most skilful of
human chemists is unable to duplicate. Every
chlorophyll bearing plant, to be sure, possesses in
greater or less measure the capacity to manufac-
ture starch and to transform this substance into a
soluble sugar. But the fact that this attribute is
characteristic of plants in general, does not make
it the less mysterious for the thoughtful observer.
The chemist is able to analyze starch, and he
tells us that it is a compound each molecule of
which contains six atoms of carbon, ten atoms of
hydrogen, and five of oxygen.
[255]
LUTHER BURBANK
But while he makes his analysis and deter-
mines the proportions of the component elements,
he is careful to assure us that these elements are
doubtless associated in very complex combina-
tions of which his analysis gives him only a vague
inkling.
If we glance at the formula by which the
chemist represents a molecule of starch — C6 H10 O5
— the thought at once suggests itself that this seems
to be a union of six atoms of carbon with five
molecules of water; for of course we are all
familiar with the formula H20 as representing
water, however little we may know of the other
niceties of chemistry.
And in point of fact, this is about the way in
which the chemist regards the matter.
Starch is a compound of water and carbon.
The plant secures the water from the soil and the
carbon from the atmosphere, where it exists in
the form of carbonic acid gas, which is given out
constantly from the lungs of every living animal.
With these simple and universally present
materials, then, the wonderful chemist of the
plant laboratory builds up the intricate sub-
stances that we term starch.
This substance is stored away in the plant
cells, not for the moment available for the purpose
of nutrition, but constituting a reserve store of
[256]
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LUTHER BURBANK
food material upon which the tissues of the plant
can draw at need.
Starch itself is insoluble in the juice of the
plant, but to make it available whenever needed,
it is only necessary for the plant chemist to add
to the compound the constituents of a molecule
of water, namely two atoms of hydrogen and one
of oxygen, and the starch is transformed into a
soluble sugar called glucose or levulose.
This substance, dissolved in the juice of the
plant, may then be transferred to the place where
it is needed; which, in the case under consid-
eration is the flesh of the fruit.
The process of starch manufacture and of
transformation of starch into sugar, with the final
storing of the sweet product in the flesh of the
prune, constitutes, as I have just suggested, one
of the most marvellous manifestations of the
power of vegetable cells. Indeed, it is precisely
this capacity that differentiates vegetable tissues
from all animal tissues whatever; for the biol-
ogists tell us that no living organism, high or
low, save only the vegetable, is capable of
manufacturing a single molecule of starch, much
less a molecule of sugar out of inorganic materials.
So a thoughtful person can scarcely fail to
regard even so plebeian a thing as a prune with
a certain measure of wonderment, almost of
[258]
The Sugar Prune and Its Parents
Mr. Burbank's Sugar Prune was developed by selection
Jrom a cross between the French prune and the Hungarian prune.
From the former it inherited sweetness and flavor and from the latter size.
It improved on each parent, however, manifesting the vigor that is
not unusual with hybrids. The French prune is still
largely grown in California, but its improved
descendants must ultimately displace it.
LUTHER BURBANK
awe, if he allows himself to reflect on the mys-
terious processes that have taken place within its
structure.
THE ELEMENTS OF VARIATION
From the present standpoint, however, we are
not so much concerned with the mysteries of plant
chemistry as with the extremely practical fact
that the new sugar prune developed in my orchard
has the fixed habit of setting its sugar-making
laboratory in operation several weeks earlier than
had been the custom with the ancestral races of
prunes.
This interesting and important change of habit
had been brought about, as the reader who has
perused the earlier chapters will surmise, by a
process of selecting, generation after generation,
the individual prunes that manifested a tendency
to early fruiting. But here as elsewhere we are
confronted with the question as to how it was
possible thus to change so markedly the habits of
a plant within a few generations.
The answer carries us back in imagination,
along lines we have followed in studying other
plant histories, to the remote ancestors of the
sugar prune.
We are led to reflect that the time of fruiting
of a given plant is largely dependent upon the
climate in which the plant habitually grows. Now
[260]
Thirty-two to the Pound
This sugar prune is particularly notable for the sweetness
of its flavor, as its name would imply. It also has an advantage
over other prunes in that it ripens in August, three weeks before the
French prune. This gives opportunity for the curing
of the prune before the wet season, a matter
of great practical importance.
LUTHER BURBANK
there must have been ancestors of the prune that
grew far to the north, for the plum is a hardy
plant. Among some of the remote and now
untraceable ancestral strains, there were doubtless
some that produced their fruit at least as early as
the first of August, perhaps even earlier.
And although (when interbreeding occurred)
the hereditary tendency to early fruiting had been
made subordinate to the late-fruiting tendencies
of other races of plums that had grown in milder
climates, yet the potentialities of early fruiting
were never altogether lost.
Hence among the multitude of seedlings that
were produced by my hybridizing experiments,
this trait, along with a multitude of other sub-
merged ancestral traits, was now able to make
itself manifest. And it was my task, by a
comparatively simple process of selection, to
make sure that the character was preserved.
The matter is perhaps made a little clearer if
we reflect that in any race of domestic plants,
there is a considerable range of variation as to
size of fruit, abundance of bearing, and time of
fruitage. Such variations represent, as we have
pointed out, the varying traits of diverse strains
of ancestors. But it must be observed that there
are always some clearly defined limits beyond
which variation does not readily go.
[262]
The Best Prune — The Burbank Standard
This six-inch prune is named the Standard. It is a cross
between the Sugar prune and the Tragedy ; and it is considered by
Mr. Burbank to be almost an ideal prune. Many experts concur in
pronouncing it the best prune ever produced. Its trees are
enormous and never Jailing bearers* and the fruit is
oj the largest size and oj splendid quality.
LUTHER BURBANK
Among all the thousands of types of prunes
grown on the seedlings of my hybrid colony or
on grafts on some receptive tree, there will be
individual fruits varying, let us say, from one-
half inch in length to perhaps two and a half
inches — but by no chance will there be a fruit
four inches in length.
Similarly among my seedlings there will be
some that ripen their fruit as early as the first of
August, but none that ripen so early as the first
of July.
Fruits of other species may ripen far earlier;
the cherry does so habitually. But the ancestors
of the plum have lived under conditions that made
it unnecessary for them to mature their fruit much
before midsummer. So their range of habit in
this regard, as recorded in the stored hereditary
tendencies, was strictly limited. And the possi-
bilities of variation among my hybrid seedlings
are correspondingly limited, because, as I have
hitherto pointed out, heredity is but the symbol of
the sum of past environments, and the hereditary
limitations of any common race of plants to-day
are determined by the aggregate limitations of all
their ancestors.
REVERSION TO THE AVERAGE
Such an analysis, in which the varying con-
ditions that environ the different strains of a
[264]
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LUTHER BURBANK
hybrid's ancestry are kept constantly in mind,
serves to give us a clue to the observed tendency
of families or strains of animals or plants to
revert in successive generations toward a given
mean or average.
It has long been observed that, as a general
rule, the offspring of human parents that are
exceptionally tall tend to be shorter than their
parents; whereas, contrariwise, the offspring of
dwarfs tend to be taller than their parents.
In studying races of animals and plants, biol-
ogists have discovered that this tendency, spoken
of as tendency to revert to a mean, is universal.
The matter has been especially studied in
recent years by the Danish biologist, Professor W.
L. Johannsen, of Copenhagen. His studies of
barley and of kidney-beans show that any given
race of these plants is really made up of a number
of subordinate races, representing different strains
of the ancestral pedigree, and that when the plants
are self -fertilized, the progeny tend to group them-
selves into a few more or less permanent types.
There are limits of variation as to size, color
and qualities but the progeny as a whole do not
tend to have offspring that approach the half-way
mark between these two extremes. Rather they
break up into groups, each group tending to
reproduce itself in such a way as to form a new
[266]
OTQ
LUTHER BURBANK
subordinate race or "pure type." Thus from the
same mixed stock sundry races of relative giants
and of relative dwarfs, as well as numerous inter-
mediate races, are formed.
Now it would appear that such a case as that
of the prune, in which we are able to work out
by artificial selection a race characterized by
tendency to early fruitage, is in keeping with these
studies of the so-called "pure lines" of descent to
which Professor Johannsen has given attention.
But it must be understood that it is exceedingly
difficult to carry the experiment in the case of
the prune to the stage at which the type becomes
absolutely fixed, for the reason that there are so
many other qualities to be considered.
This matter of varying qualities represented in
the same seed we have discussed before, and we
shall have occasion to refer to it again and again.
Here it suffices to note that the case of the prune
is akin to others that we have examined, for
example the hybrid walnuts and the early cherries,
in that the qualities for which we have bred are
so numerous and so varied that they can be
aggregated only in one seedling among many
thousands, and could not be fixed without a long
series of generations of additional breeding.
Fortunately this is of no practical consequence,
because the prune, like other orchard fruits, may
[268]
THE SUGAR PRUNE
best be propagated by grafting. From a single
seedling we may thus develop, in due course, an
entire orchard or a series of orchards.
Such is in practice the method of propagating
the sugar prune. It is obvious that plants thus
grown partake of the very substance of the
original seedling; they are part and parcel of it,
and fruit grown from such grafts will be uniform
in quality, within the limits of variation that char-
acterize the individual specimens of any fixed
race.
— When I say that something
like seven and a half million
seedlings of the plum have
passed under my hand and
eye in the course of my
many series of experiments
in the perfection of this
fruit, the reader will not
wonder that each individual
cross has not been recorded.
The Petunia
Mr. Burbank has made many very interesting breeding
experiments with the Petunia. Samples oj his productions are
shown in this color reproduction. Perhaps the most interesting single
experiment with this flower was that in which Mr. Burbank hybridized the
Petunia and the Tobacco plant. The resulting hybrid was a very
curious plant which combined the characteristics oj both parents.
Mr. Burbank named it the Nicotunia. It was facetiously
described as a petunia that had acquired the tobacco
habit. Unfortunately the hybrids lacked vitality \
and did not produce a permanent race.
SOME INTERESTING FAILURES
A PETUNA WITH THE
TOBACCO HABIT — AND OTHERS
A WELL KNOWN and appreciative critic,
after a visit to Santa Rosa, commented
on my work in a way that seemed to
suggest that what most appealed to him was the
great variety of experiments constantly being
carried on.
"Every plant seems to appeal to Luther Bur-
bank," he said. "This appeal is quite unlike the
appeal that is made to the botanist or even to
the horticulturist; Burbank likes it because it is
a plant and because he would like to try to modify
it. Therefore he grows everything he can, no
matter where it comes from or of what kind. He
cultivates with personal care, multiplies the stock
to the limit of his capacities, scrutinizes every
variation, hybridizes widely, saves the seeds of
the forms that most appeal to him, sows again,
hybridizes and selects again, uproots by the hun-
[VOLUME II — CHAPTER IX]
LUTHER BURBANK
dreds and thousands, extracts the delights from
every new experience, and now and then saves
out a form that he thinks to be worth introducing
to the public.
"Every part of the work is worth the while of
itself; at every stage the satisfaction of it is reason
enough for making and continuing the effort.
Every form is interesting, whether it is new or the
reproduction of an old form. He shows you the
odd and intermediate and reversionary forms as
well as those that promise to be of general use.
"All this leads me to say that the value of Mr.
Burbank's work lies above all merely economic
considerations. He is a master worker in making
plants to vary. Plants are plastic material in
his hands. He is demonstrating what can be done.
He is setting new ideals and novel problems.
"Heretofore, gardeners and other horticul-
turists have grown plants because they are useful
or beautiful : Mr. Burbank grows them because he
can make them take on new forms. This is a
new kind of pleasure to be got from gardening, a
new and captivating purpose in plant growing.
It is a new reason for associating with plants.
Usually I think of him as a plant-lover rather than
plant-breeder. It is little consequence to me
whether he produces good commercial varieties
or not. He has a sphere of his own, and one that
[272]
Tobacco Plant
Mr. Burbank has made important experiments with
various members of the tobacco tribe. This picture shows a
specimen oj unusual vigor oj growth* illustrating the possibilities of
development in that direction. Mr. Burbank s experiments with the
plants of this familv have largely been made for their scientific
interest rather man in the attempt to develop commercial
varieties. Not being a user of tobacco himself, he
does not take the personal interest in the
latter aspect of the work that he
otherwise might.
LUTHER BURBANK
should appeal to a universal constituency. In
this way, Luther Burbank's work is a contribution
to the satisfaction of living, and is beyond all
price."
Such appreciative notices of one's work are of
course agreeable, and I am bound to admit that
what is said about my love of experimenting with
any and every kind of plant is altogether true.
There is one point, however, at which I am
forced to part company with the commentator.
To me it is a matter of vital consequence as to
whether I "produce good commercial varieties or
not." It is necessarily so, inasmuch as I have all
along made a living by the sale of the products of
my experiments.
Had I not produced good commercial varieties,
my practical success would have been something
quite different from what it has been.
Nevertheless, it of course is true that the suc-
cessful commercial varieties of plants and fruits
are comparatively few in number as contrasted
with the vast numbers of forms with which I have
experimented. It could not well be otherwise,
for it would be a strange and novel form of
experiment that led always to success. But of
course the public in general hears of, and in the
main cares for, successes only. There is seldom
any reason for exploiting a failure. And so my
[274]
SOME INTERESTING FAILURES
long list of experiments that have led to no
practical result has scarcely been heard of by the
public in general.
Some of these, however, are in themselves
highly interesting, and I have thought it worth
while to take the reader into my confidence to the
extent of telling about three or four series of
experiments which produced no permanent new
forms of flower or fruit, and which from the
commercial standpoint resulted only in loss of
time and money.
There are certain lessons to be drawn from
these that I think will command the reader's
attention and interest.
A MISGUIDED PETUNIA
One of the most curious hybridizing experi-
ments that I ever performed consisted of crossing
the common garden petunia with a variety of
tobacco, known as Nicotiana Wigandioides rubra.
In this cross the petunia pollen was used to
fertilize the pistil of the tobacco plant. The seed
thus produced was planted in the summer, as
soon as it ripened, and possibly two hundred
plants were raised.
When about a foot high the plants were placed
in boxes in the greenhouse to keep over winter.
They revealed no inclination to bloom, nor did
they vary greatly from the parent tobacco plant,
[275]
A Tobacco Hybrid
In hybridizing the Petunia and the Tobacco, Mr. Burbank
used the tobacco as the mother parent. The offspring at first
resembled the tobacco plant, but subsequently they showed great diversity
of form, some of them becoming trailers like the petunia. The speci-
men here shoum is a hybrid between two relatives of the tobacco,
the Nicotiana Wigandoides rubra and the Nicotiana
glauca. The crossing of the petunia and the
tobacco has peculiar interest because the
plants belong to different genera.
SOME INTERESTING FAILURES
except in the matter of growth, which was very
uneven, some of the hybrids being two or three
times as large as others. The foliage was some-
what unusual; yet its resemblance to the tobacco
was so great that a casual observer would have
doubted whether the cross had really been made.
In a word, the characteristics of the tobacco
plant seemed to preponderate.
But towards spring, when the plants were set
again out of doors, they soon began to show the
influence of their mixed heritage. Some of them
turned crimson, and others pink; yet others
remaining green. Moreover, the plants them-
selves developed a great diversity of habit. Even
during the winter some of them had begun to
fall over and show a tendency to trail like vines.
As the second season advanced, some of these
became genuine trailers like the petunia, and
produced blossoms altogether different in color
from the red flowers of the tobacco plant.
These plants did not bloom very abundantly,
but their great diversity of form and peculiarity
of foliage and flower made them a very striking
lot of plants.
Some of them grew four or more feet in height
with large tobacco-like leaves, and others were
trailing dwarfs that to all appearances might have
belonged to an entirely distinct race.
[277]
LUTHER BURBANK
The plants that closely resembled the tobacco
parent were, for the most part, weeded out. The
ones that gave evidence of their hybrid origin
were carefully nurtured. But it was noticed
towards fall that although the tops grew splen-
didly, there seemed to be an unusual lack of
roots. The plants would come to a certain size,
and then take on what could perhaps be best
described as a "pinched" appearance, from lack
of vitality incident to their defective roots. There
was, however, a great difference among the indi-
vidual plants, some of them remaining strong
throughout the season.
When the plants were taken up, it appeared
that the sickly ones had produced only a few
long, frail, wiry roots. It appeared to have been
impossible for them to develop a thoroughly good
root system. Evidently most of the new plants
had inherited the rank-growing tops of the giant
tobacco and the smaller, less efficient roots of the
petunia.
A visitor whose attention was called to this
peculiarity remarked facetiously that my petunias
had obviously been stunted in growth and vitality
through acquiring the tobacco habit, just as boys
are stunted when they make the same mistake.
It is only fair to recall, however, that the
petunias had no choice in the matter. Their
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LUTHER BURBANK
association with the tobacco had been thrust upon
them.
Owing to the lack of vitality of the hybrids,
and the fact that they seemed unlikely to develop
additional characteristics of exceptional interest,
the plants were not especially sheltered, and they
perished from freezing during the ensuing winter.
Thus the experiment of hybridizing the petunia
and the tobacco came to an end; not, however,
without illustrating one or two suggestive points
of plant breeding to which further reference will
be made in due course.
SOME MONGREL POTATOES
Inasmuch as my first experiments in plant
breeding had to do with the potato, it is not
strange that the tribe of plants to which this
vegetable belongs have always had for me a
rather exceptional interest.
Early in the course of my California work I
secured specimens of a remote cousin of the culti-
vated potato which grows in our southwestern
States and which is known to the Indians as the
Squaw potato (Solanum Jamesii).
It is a wild rambling potato, spreading in all
directions by tubers that seem to be connected by
long strings. Although used for food by the
Indians, this potato is hardly worth the notice of
the gardener, except for its hardiness. This
[280]
SOME INTERESTING FAILURES
trait suggested that it might possibly be crossed
to advantage with other species. But although
several crosses were effected with other species
of the potato, nothing of value came of them.
An allied species, however, namely the
Solarium Commersoni, a worthless form intro-
duced from Europe, gave more interesting results.
This plant, although recommended as a valu-
able commercial product, really had very little
value. Like most wild potatoes, it scattered its
tubers widely from the hill; moreover it had a
bitter taste that made it unpalatable. The blos-
soms, however, were handsome, and, unlike the
blossoms of the ordinary potato, they were quite
fragrant.
Moreover, the blossoms were produced in
astounding profusion. But they did not ordinarily
produce seed. When I crossed the plant with
other tuberous Solanums, however, I produced a
number of seed balls. By cross-fertilization the
plants had acquired a virility that they otherwise
lacked.
These hybrid seeds produced many strange
forms of potato plants. Some had extremely large
blossoms in great quantities, others extremely
small ones; the blossoms varied in all shades
from deep blue through sky blue to red and white.
Some of the blossoms might have been thought
[281]
Tomato-Potato Grajt
The grafting of potato tops on tomato roots and of tomato
tops on potato roots have constituted some of the most interesting
of Mr. Burbank's grafting experiments. The manner of grafting is not
altogether unlike that employed in the case of trees, but the experi-
ment has peculiar interest because Mr. Burbank has been
able to unite the stems of these plants, but has not
been able to cross-polfenate them successfully.
SOME INTERESTING FAILURES
not unworthy to be introduced as garden orna-
ments. But they offered no advantage over
numerous flowers already in existence, and as
the tuber proved worthless, these experiments
also were discontinued.
But by far the most interesting experiments
that I have made with the wild potatoes were
made by combining the form known as the Dar-
win potato (Solarium maglia), a yellow fleshy
tuber with big seed balls, with the common
potato, and with various other tuberous Solanums.
Thus I produced a plant which yielded balls of
fruit at least three or four times as large as those
ever produced by the ordinary potato.
In one case, the fruit of this hybrid proved to
have an excellent flavor, in some respects superior
in quality to the tomato. It was white when ripe,
and had also a highly pleasing aroma. The flesh
of this fruit resembled that of a firm tomato. To
the taste it suggested a delightful commingling
of acids and sugars.
As the fruit grew on a hybrid potato vine, and
in itself had much the appearance of a tomato, it
was christened the "Pomato."
The name itself was appropriate enough, but
was unfortunate in that it led to the unauthor-
ized assumption that the fruit was really a cross
between the tomato and the potato. In point of
[283]
LUTHER BURBANK
fact, I have never been able to cross these two
plants, and there was no strain of the tomato in
the ancestry of the new fruit.
The pomato plant produced fruit abundantly,
but very few tubers, and when the latter were
planted, the vines seemed to run out, giving their
entire attention to the production of seed balls.
But the seed when planted never reproduced
itself exactly true to form, showing its hybrid
quality by the production of unique and abnormal
forms.
Thus there was no practical method of prop-
agating the pomato, the tubers being wholly
absent or merely rudimentary, and the seed not
producing a satisfactory product.
It is probable that if I could have found time
to continue the experiments, I should have been
able to fix the race through selection, and thus
have added a fruit of an altogether new variety
to the list of garden products.
But to have done this would have necessitated
experiments on a large scale, and this would
have required more time than I could give at the
moment.
I think it not unlikely, however, that some one
will take up the experiment in future and develop
a fruit comparable to my pomato that will have
commercial value.
[284]
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LUTHER BURBANK
One of the most curious hybridizing experi-
ments that I have ever conducted was made in an
effort to test the limitations of affinity between
the various members of the rose family. I had
on my place a bush of the California dewberry,
a plant that differs from most other members of
the family in that its staminate and pistillate
flowers are borne separately.
The particular bush in question had only
pistillate flowers, and as it grew in isolation, it
ordinarily bore no fruit, as its flowers were seldom
fertilized. At most it occasionally developed
single drupelets, a result no doubt of partial
fertilization from grains of pollen accidentally
brought from a distance by wind or insect.
The isolation of the plant, and the fact
that it bore unisexual flowers, seemed to offer a
favorable opportunity for experiment.
SOME HYBRID BERRIES
Upon this plant I applied the pollen of various
species of plants of the same family. The list
is a striking one, for it included the apple, the
mountain-ash, the hawthorn, the quince, the pear,
and various kinds of roses.
I worked at these hybridizations attentively
during the blooming season of the dewberry in
the summer of 1886.
The pistils thus fertilized developed an abun-
[286]
SOME INTERESTING FAILURES
dant crop of fruit, and in the ensuing season I
raised from these berries between five and six
thousand seedlings.
Never on earth, perhaps, was there seen a
more widely varying lot of seedlings that were
the immediate offspring of a single plant. The
hybrids took almost every possible form that
could be suggested as combining the traits of
the various parent plants. Most of them were
absolutely thornless. Many grew upright like the
apple tree, showing nothing of the drooping
tendency even of the raspberry, much less the
trailing habit of the dewberry. The leaves were
generally quite smooth, some resembling those of
the pear, others being partially trifoliate, and
most of them assuming strange and unusual
forms.
When this motley company came to the time
of blooming, there was still another surprise, for
the flowers were as varied as the foliage. Some
of the blossoms were crimson in color, and half
as large as an apple blossom; some were pink
and quite small; others were white. A large
number of plants, however, did not bloom at all,
although they were attentively cared for, and
were otherwise normal.
From these strange hybrids I not unnaturally
expected to raise a remarkable variety of fruits.
[287]
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SOME INTERESTING FAILURES
I had hopes even of being able to produce some-
thing of real value, at any rate from the second
generation.
But when it came time for the fruits to ripen,
another surprise awaited me; only two plants out
of the five thousand produced a single fruit.
One of these was a plant somewhat resembling
a raspberry bush, and this produced a number
of ill-tasting berries of a yellowish-brown. The
other bush produced insignificant fruits of an
orange-yellow color.
Though unpromising in themselves, these fruits
were carefully watched and guarded, for I felt
convinced that possibilities of strange variation
were contained in them, if only I could get from
them a few seedlings. But when the fruits were
fully matured, I examined the seeds and found
all of them hollow. They were nothing but shells,
containing no kernel.
So by no possibility could I get a single seed-
ling of a succeeding generation.
Some of the most curious of the plants were
preserved for another season, but they proved as
unproductive as before; and as I needed the
ground for other purposes I felt constrained to
destroy the entire company of curious hybrids.
In all my experience I never destroyed a lot of
plants with more sincere regret.
[289]
LUTHER BURBANK
An experiment perhaps even bolder was made
at about the time of my experience with the
hybrid dewberries. This was the hybridization of
the strawberry and the raspberry.
The attempt to cross plants of such unlike
appearance would seem to most experimenters
absurd. Yet the cross was successfully effected.
The raspberry was selected as the pistillate plant,
and pollen was applied from whatever strawberry
was at hand. It was impossible to choose as to
the latter point, for the strawberry is for the most
part out of season when the raspberry blossoms.
I had to use such material as I could find.
The pollenation proved effective, and the rasp-
berry plant produced a full crop of fruit.
There is no very marked immediate effect
observable from such a hybridization. The pulp
of the berry seems not to be affected; but the
essential seeds within the berry are enormously
modified, as the sequel showed. For when the
raspberry seeds were planted in the greenhouse,
the young hybrid plants that came up in profusion
had all the appearance of ordinary strawberry
plants. No one who inspected them casually
would suspect their hybrid origin.
The raspberry, the pistillate parent on which
the seeds had grown, has leaves with five leaflets.
But there was no leaf of this character among all
[290]
jk^m*^
Leaves of Strawberry-Raspberry Hybrids
The strawberry-raspberry hybrids produced by Mr. Bur-
bank had leaves which were uniformly trifoliate, but which varied
greatly in size and shape. Characteristic samples of the different forms
are here shown. It was peculiarly to be regretted that the hy-
brids were not fertile, as a new and highly interesting
form of fruit would doubtless have resulted had it
been possible to establish a permanent race
combining the blood of the straw-
berry and the raspberry.
LUTHER BURBANK
the hybrids; without exception their leaves were
trifoliate like the leaf of the strawberry.
In other words, in the matter of foliage, the
strawberry plant was entirely prepotent or domi-
nant, and the characteristics of the other parent
were latent or recessive.
When the hybrids were old enough, they were
carefully set out in rows in the open field. For
a month or more after transplanting they showed
no inclination to depart from the habit of the
strawberry. To close inspection it might appear
that the main stem was unusually thick, and that
the leaves were a little more wrinkled than is
usual with the strawberry, and their edges slightly
more serrated. But aside from this, the hybrid
plants were seemingly true strawberries.
About the first of June, however, the plants
began to throw out underground stolons, whereas
strawberry runners are normally on the surface.
These stolons suggested roots of the raspberry,
yet the new plants that sprang from them here
and there were exactly like the strawberry plants.
So at this stage it would seem that the influence
of the mother parent had been but slight.
But along in July came the transformation.
Rather suddenly each main plant sent up two,
three, or more strong smooth canes, which grew
to the height of from two to five feet. These
[292]
SOME INTERESTING FAILURES
canes were absolutely thornless, as were all other
portions of the plant; they were as smooth as
strawberry plants in leaf and stem, but their form
and manner of growth now departed strangely
from the traditions of the trailing parent.
Obviously the influence of the raspberry
parent had at last made itself potent.
Some of the plants were yellowish, indicating
that the berries would probably be yellow; others
were reddish. There were no blossoms the first
season, but the ensuing year panicles of blossoms
of great size were put forth, some of the bunches
being twelve inches in breadth — far larger than
those usually seen on the raspberry. In a single
panicle there were sometimes several hundred
flowers. The individual blossoms were generally
larger than the flowers of the raspberry, but
slightly smaller than those of the strawberry.
In the center of each blossom was a miniature
berry, which might be said to resemble either a
strawberry or a raspberry, being so small that
its exact characteristics could hardly be dis-
tinguished.
I was quite sure I had a valuable cross, and
that at least one might be found among the many
that would produce fruit. But in this I was
disappointed; not a plant produced a single
berry. The miniature fruit remained unchanged
[293]
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SOME INTERESTING FAILURES
in size until it finally dropped from the bush in
the fall.
The following season a few of the plants bore
one or two fruits having two or three drupelets
each, like mere fragments of a normal raspberry.
But not a seed was found. The plants were as
sterile as mules. So here the experiment ended,
and the hybrid strawberry-raspberries followed
the hybrid dewberries to the brush heap.
WHY THE EXPERIMENTS FAILED
If now we consider the results of these various
experiments, it will be clear that they have certain
elements in common. In all cases the hybridizing
was effected between species that are botanically
related. Some of them (petunia and potato, dew-
berry and its mates, strawberry and raspberry)
belonged to different genera, however, and in no
case was the relationship between the mated
forms very close. And this fact is of course of
salient importance in enabling us to comprehend
the results.
It is almost axiomatic to say that the hybrid-
izing of plants becomes increasingly difficult in
proportion as the attempt is made to cross more
and more distantly related species. Even within
the same genus it is very often impossible to
produce a hybrid that is not sterile.
I might cite in further illustration of these
[295]
LUTHER BURBANK
difficulties the experiments through which I have
hybridized the apple with the pear, and with the
quince; the cherry with the plum; and the peach
with the almond, with the Japanese plum, and
with the apricot, without in any of these cases
producing a product of value. These crosses,
like the ones just detailed, bring together racial
tendencies that are too widely divergent to be
harmonized.
It would appear that it is essential to the differ-
entiation and perpetuation of species that bounds
should be set on the possibility of producing a
disturbing influence through hybridization. When
plants, even though sprung from the same origin,
have diverged so widely and for such periods of
time as to produce forms differing from one
another so greatly as, for example, the mountain-
ash, the apple, and the rose differ from the dew-
berry; or the strawberry from the raspberry — it
would seemingly not be advantageous in the
scheme of evolution to permit the hybridizing of
these forms.
The mutations that would be produced, were
such hybridization to result in virile offspring,
would be too divergent, in all probability, to fit
into their environment successfully. At all events
the possibility of such crosses would constitute a
disturbing influence that would rob the scheme
[296]
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LUTHER BURBANK
of organic nature of a good deal of its orderly
character.
And so it appears, so far as may be judged
from my experiments, that even when hybrids
between these divergent forms are produced, the
offspring are sterile, and the results of the hybridi-
zation are not perpetuated.
Such, then, is the barrier that nature erects
in the interest of race preservation, between
species that have widely diverged.
But, on the other hand, we have seen many
illustrations of the fact that when species a little
more closely related are hybridized, the result
may be not to produce sterility but to give added
virility to the offspring.
We saw this illustrated, for example, when the
walnut of the eastern United States was crossed
with the black walnut of California. The hybrid
progeny not only showed tremendous individual
vitality, growing with great rapidity and to
enormous size, but they produced an altogether
extraordinary abundance of fertile fruit.
The hybrid variety thus produced — named, it
will be recalled, the "Royal" — constitutes a new
race that can more than hold its own against the
parent forms.
And the reason for this, seemingly, was that
the two species of walnut had not become suffi-
[298]
SOME INTERESTING FAILURES
ciently divergent to introduce a greater diversity
of conflicting tendencies than is consonant with
racial progress when the strains are brought
together.
But it will be recalled that when the California
black walnut was hybridized with the English
walnut — producing the "Paradox" — the results in
this regard were quite different. While the indi-
vidual offspring showed great vitality, they were
almost sterile, producing only a few stray nuts in
contrast with the profusion of the Royal hybrids.
And we may infer from this result that the
California walnut and its remote English cousin
have diverged to a point lying just on the border
line of the limits of desirable racial mingling.
These limits have not quite been crossed as
they have been in the case of the dewberry and
apple tree, and the strawberry and raspberry, but
they are being approximated; and there is no
probability that the hybrid offspring of the black
walnut and the English walnut could maintain
itself through successive generations as a new race
in a state of nature. At all events, its fight would
be a doubtful one.
THE APPLICATION TO THE HUMAN SPECIES
It is more than likely, then, that the lessons
taught by the unsuccessful experiments recorded
in this chapter are quite as important as if they
[299]
The Perfected Solarium
A later stage of development of the new Brazilian Solanum
shown on page 297. Mr. Burbank has now developed the Jruit
by selective breeding until it is oj considerably increased size, and
markedly improved in flavor. A Jew more lessons need to
be given bejore the plant is marketable; but the
new Solanum promises to be a valuable
addition to the vegetable garden.
SOME INTERESTING FAILURES
had led to seemingly more practical results. For
they serve to emphasize a great fundamental
truth of heredity, which has a more important
bearing on the problems of racial development
of all organic beings, including man himself. It
has become more and more clear in recent years
that the underlying principles of evolution apply
in large measure to plants and animals alike,
and that much may be learned about the proper
breeding of mankind from a direct study of the
breeding of the lower organisms.
And as regards the particular case under con-
sideration, it is scarcely to be doubted that we
may draw important lessons from the obvious
results of the hybridizing of plants to apply to
the commingling of human races.
It is commonly held that the various existing
races of man constitute a single species. But this
classification was made under the influence of the
old idea that sterility of offspring is a valid test
of specific difference. No one nowadays holds
that view, with regard to plants at any rate, and
the view is probably no more valid in its appli-
cation to a great number of animals, including
man himself.
But, in any event, the question as to whether
mankind constitutes a single species or several
species is a matter of definition of no real impor-
[301]
LUTHER BURBANK
tance. It is beyond question that the human
family comprises widely divergent races, and it
is scarcely open to question that the divergencies
in many cases are so pronounced as to make
hybridization between these races inexpedient,
even though it still is possible.
The student of history tells us that the great
civilized races of the past were all mixed races.
This was true of the Egyptians, the Babylonians,
the Greeks, and the Romans. It is true of the
chief nations of to-day.
But the races that intermingled to produce the
great peoples have always been somewhat closely
related. No good result has ever been achieved,
for example, by the commingling of Mongolian
and Aryan blood, or of Aryan with Negro. Such
wide crosses must be expected to produce at least
a measure of infecundity, and a commingling of
racial tendencies too divergent to be advanta-
geously blended.
The case is comparable to that of the Paradox
walnut, even though it be not quite so extreme
as the case of the hybrid strawberries and dew-
berries.
But what chiefly concerns us now is not the
past history of mankind, but the present and
future history; and in particular the history of
mankind here in America. There is taking place
[302]
Aid Jrom the Butterfly
This picture shows the butterfly at work on the Prince's
Feather or Cockscomb flower. The butterfly plays 6y no means so
important a part as the bee in plant fertilization, yet it constantly trans-
ports pollen* and there are many types oj tubular flowers that
depend entirely on butterflies or rnothis for cross-fertili-
zation. We think of the butterfly as leading an
absolutely aimless life, but it is a very use-
ful citizen in the flower garden.
LUTHER BURBANK
in our day what is doubtless the greatest migration
in all history. The races of Europe are flooding
into America, and there is a more pronounced
commingling of racial strains now taking place
on our soil, than perhaps ever occurred in any
one place, or in any single epoch, in the history
of the world.
America owes its present greatness in consid-
erable measure to the mingling of moderately
divergent strains in the past; but this fact should
not blind us to the menace that lies in the
mingling of races that are too divergent to blend
advantageously.
And it is at least an open question whether
certain of the Latins, the varied races of Slavs,
and the vast hordes of Semites that have come
to us in recent years can mingle their racial strains
with the Anglo-Saxon stock without disadvantage
to the ultimate progeny.
It is this thought that I would put forward as
the most important suggestion that arises from
the study of the hybridizing experiments in which
I unsuccessfully attempted to blend the hereditary
tendencies of certain races of plants that were too
widely divergent.
[END OF VOLUME II]
LIST OF
DIRECT COLOR PHOTOGRAPH PRINTS
IN VOLUME II
Blackberry page
The Crystal White, So Called 41
The Lawton Blackberry ; 43
Signs of Success — Yellow White Berries 46
Some Leaf Variations 51
Like Leaf — Like Fruit 53
Color Variations in the Stems of the Blackberry 56
Some Stems of the Blackberry's Cousin 57
The Stem Finally Selected 60
Baby Berries Awaiting Selection 63
White Blackberries on the Bush 66
Burbank White Blackberries 71
Calla
The Spadix of a Calla Lily 77
A Freak Calla 81
Another Freak Calla 85
Mr. Burbank 's Original Yellow Calla 89
White and Yellow Callas 93
The Scented Calla 99
Cherry
Preparing for PoIIenation 200
Ready for PoIIenation 203
Seeking Aid of the Bee 205
Too Much Stone 207
On The Tree 210
At $3.10 a Pound 213
The Ideal Cherry Tree 215
The Earliest Cherry 217
A Yearling Cherry 219
A Black Giant 22 1
The Improved Giant 223
A Stalwart Infant 225
The Abundance Cherry 227
Truly Abundant 231
LIST OF ILLUSTRATIONS (Continued)
Cockscomb P^
Aid From the Butterfly 303
Daisy
Shasta Daisies by Mr. Burbank 's Porch Frontispiece
The Shasta Daisy 6
Original New England Ox-Eyes 9
The Shasta Daisy and Two of Its Parents 1 1
The Shasta and Another European Ox- Eye 15
Shastas as High as the Fence 19
A Typical Shasta Daisy Bush 21
563 Buds and Blossoms 22
A Million Shasta Daisies in a Row 25
Evidence of Chrysanthemum Cousinship 28
Many Steps Toward a Given End 31
Three Shastas From Different Lots 35
A Sport Among the Shastas 37
Exotics
Rare Exotics 279
Petunia
The Petunia 270
Plum
Large Plum With Small Seed 102
Standard Plum With Large Stone 104
A Plum With Small Stone and Much Meat 105
A Typical Stoneless Plum 109
Peach and Almond Stones Compared 1 14
A Stoneless Seedling 117
An Improved Stoneless Seedling 119
Three Stages of Development 121
Seedling Plum With Stem Attached 125
One Result of Stonelessness 127
Double Seeds Take the Place of a Stone 129
Another Stoneless Plum Compromise 131
Many Plums on One Tree 133
Ancestor and Descendant 135
Potato
Step-Mothered Potatoes 285
LIST OF ILLUSTRATIONS (Continued)
Prune F^
Prune-Drying 234
The Giant Prune 237
After the Lye Bath 241
A Peeled Giant 244
A Stoneless Prune 247
Prune Dipping 250
A Result of Over-Dipping 253
Too Free a Stone 257
The Sugar Prune and Its Parent 259
Thirty-two to the Pound 261
The Best Prune — the Burbank Standard 263
A Luscious Fruit 265
The Standard Prune After Drying 267
Rhubarb
Crimson Winter Rhubarb 171
The Blossom of the Rhubarb 175
Giant Rhubarb and Crimson Winter Rhubarb 177
A $1,200 Acre 18:
A Lone Giant 185
Another View of the Giant 189
Ready for Shipment 193
Roots of the Rhubarb 195
A Christmas Gift 198
Seed
Seed-Time 294
Solanum
A Brazilian Solanum 297
The Perfected Solanum 300
Strawberry
The Strawberry-Raspberry Hybrid 288
Leaves of Strawberry- Raspberry Hybirds 291
Tobacco
Tobacco Plant 273
A Tobacco Hybrid 276
Tomato
Tomato-Potato Graft . . . 282
LIST OF ILLUSTRATIONS (Continued)
Walnut Page
A Sixteen Year Old Paradox 139
The Blossom of the Walnut 141
A January I Walnut Graft 144
The Same Graft Six Months Later 145
Wood of the Paradox 149
Two Inches in Diameter in One Year 151
Variation in Walnut Leaves 153
Black Walnuts 155
Some English Walnuts 157
A Grafted Walnut Stump 161
$20,000 Worth of Walnut Seedlings 163
Some Japanese Walnut Variations 165
Wood of the Royal Walnut 167
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