It is well known that Darwin based his theory of natural selection to a
large extent upon the experience of breeders. Natural and artificial
selection exhibit the same general features, yet it was impossible in
Darwin's time to make a critical and comparative analysis of the two
processes.
In accordance with our present conception there is selection of species
and selection within the species. The struggle for life determines which
of a group of elementary species shall survive and which shall
disappear. In agricultural practice the corresponding process is usually
designated by the name of variety-testing. Within the species, or within
the variety, the sieve of natural selection is constantly eliminating
poor specimens and preserving those that are best adapted to live under
the given conditions. Some amelioration and some local races are the
result, but this does not appear to be of much importance. On the
contrary, the selection [605] within the race holds a prominent place in
agriculture, where it is known by the imposing term, race-breeding.
Experience and methods in horticulture differ from those in agriculture
in many points. Garden varieties have been tested and separated for a
long time, but neither vegetables nor flowers are known to exhibit such
motley groups of types as may be seen in large forage crops.
New varieties which appear from time to time may be ornamental or
otherwise in flowers, and more or less profitable than their parents in
vegetables and fruits. In either case the difference is usually
striking, or if not, its culture would be unprofitable.
The recognition of useful new varieties being thus made easy, the whole
attention of the breeder is reduced to isolating the seeds of the
mutants that are to be saved and sown separately, and this process must
be repeated during a few years, in order to produce the quantity of seed
that is needed for a profitable introduction of the variety into
commerce. In proportion to the abundance of the harvest of each year
this period is shorter for some and longer for other species.
Isolation in practice is not so simple nor so easy an affair as it is in
the experimental garden. Hence we have constant and nearly unavoidable
[606] cross-fertilizations with the parent form or with neighboring
varieties, and consequent impurity of the new strain. This impurity we
have called vicinism, and in a previous lecture have shown its effects
upon the horticultural races on one hand, and on the other, on the
scientific value that can be ascribed to the experience of the breeder.
We have established the general rule that stability is seldom met with,
but that the observed instability is always open to the objection of
being the result of vicinism. Often this last agency is its sole cause;
or it may be complicated with other factors without our being able to
discern them.
Though our assertion that the practice of the horticulturist in
producing new varieties is limited to isolation, whenever chance affords
them, is theoretically valid, it is not always so. We may discern
between the two chief groups of varieties. The retrograde varieties are
constant, the individuals not differing more from one another than those
of any ordinary species. The highly variable varieties play an important
part in horticulture. Double flowers, striped flowers, variegated leaves
and some others yield the most striking instances. Such forms have been
included in previous lectures among the ever-sporting varieties, because
their peculiar characters oscillate between two extremes, viz: [607] the
new one of the variety and the corresponding character of the original
species.
In such cases isolation is usually accompanied by selection: rarely has
the first of a double, striped or variegated race well filled or richly
striped flowers or highly spotted leaves. Usually minor degrees of the
anomaly are seen first, and the breeder expects the novelty to develop
its features more completely and more beautifully in subsequent
generations. Some varieties need selection only in the beginning, in
others the most perfect specimens must be chosen every year as
seed-bearers. For striped flowers, it has been prescribed by Vilmorin,
that seeds should be taken only from those with the smallest stripes,
because there is always reversion. Mixed seed or seed from medium types
would soon yield plants with too broad stripes, and therefore less
diversified flowers.
In horticulture, new varieties, both retrograde and ever-sporting, are
known to occur almost yearly. Nevertheless, not every novelty of the
gardener is to be considered as a mutation in the scientific sense of
the word. First of all, the novelties of perennial and woody species are
to be excluded. Any extreme case of fluctuating variability may be
preserved and multiplied in the vegetative way. Such types are
designated [608] in horticulture as varieties, though obviously they are
of quite another nature than the varieties reproduced by seed. Secondly,
a large number, no doubt the greater number of novelties, are of hybrid
origin. Here we may discern two cases. Hybrids may be produced by the
crossing of old types, either of two old cultivated forms or newly
introduced species, or ordinarily between an old and an introduced
variety. Such novelties are excluded from our present discussion.
Secondly, hybrids may be produced between a true, new mutation and some
of the already existing varieties of the same species. Examples of this
obvious and usual practice will be given further on, but it must be
pointed out now that by such crosses a single mutation may produce as
many novelties as there are available varieties of the same species.
Summarizing these introductory remarks we must lay stress on the fact
that only a small part of the horticultural novelties are real
mutations, although they do occur from time to time. If useful, they are
as a rule isolated and multiplied, and if necessary, improved by
selection. They are in many instances, as constant from seed as the
unavoidable influence of vicinism allows them to be. Exact observations
on the origin, or on the degree of constancy, are usually lacking, [609]
the notes being ordinarily made for commercial purposes, and often only
at the date of introduction into trade, when the preceding stages of the
novelty may have been partly forgotten.
With this necessary prelude I will now give a condensed survey of the
historical facts relating to the origin of new horticultural varieties.
An ample description has been given recently by Korshinsky, a Russian
writer, who has brought together considerable historical material as
evidence of the sudden appearance of novelties throughout the whole
realm of garden plants.
The oldest known, and at the same time one of the most accurately
described mutations is the origin of the cut-leaved variety of the
greater celandine or _Chelidonium majus_. This variety has been
described either as such, or as a distinct species, called _Chelidonium
laciniatum_ Miller.
It is distinguished from the ordinary species, by the leaves being cut
into narrow lobes, with almost linear tips, a character which is, as we
have seen on a previous occasion, repeated in the petals. It is at
present nearly as commonly cultivated in botanical gardens as the _C.
majus_, and has escaped in many localities and is observed to thrive as
readily as the native wild [610] plants. It was not known until a few
years before the close of the 16th century. Its history has been
described by the French botanist, Rose. It was seen for the first time
in the garden of Sprenger, an apothecary of Heidelberg, where the _C.
majus_ had been cultivated for many years. Sprenger discovered it in the
year 1590, and was struck by its peculiar and sharply deviating
characters. He was anxious to know whether it was a new plant and sent
specimens to Clusius and to Plater, the last of whom transmitted them to
Caspar Bauhin. These botanists recognized the type as quite new and
Bauhin described it some years afterwards in his Phytopinax under the
name of _Chelidonium majus foliis quernis_, or oak-leaved celandine. The
new variety soon provoked general interest and was introduced into most
of the botanical gardens of Europe. It was recognized as quite new, and
repeated search has been made for it in a wild state, but in vain. No
other origin has been discovered than that of Sprenger's garden.
Afterwards it became naturalized in England and elsewhere, but there is
not the least doubt as to its derivation in all the observed cases.
Hence its origin at Heidelberg is to be considered as historically
proven, and it is of course only legitimate to assume that it originated
in [611] the year 1590 from the seeds of the _C. majus_. Nevertheless,
this was not ascertained by Sprenger, and some doubt as to a possible
introduction from elsewhere might arise. If not, then the mutation must
have been sudden, occurring without visible preparation and without the
appearance of intermediates.
From the very first, the cut-leaved celandine has been constant from
seed. Or at least it has been propagated by seed largely and without
difficulty. Nothing, however, is known about it in the first few years
of its existence. Later careful tests were made by Miller, Rose and
others and later by myself, which have shown its stability to be
absolute and without reversion, and it has probably been so from the
beginning. The fact of its constancy has led to its specific distinction
by Miller, as varieties were in his time universally, and up to the
present time not rarely, though erroneously, believed to be less stable
than true species.
Before leaving the laciniate celandine it is to be noted that in crosses
with _C. majus_ it follows the law of Mendel, and for this reason should
be considered as a retrograde variety, the more so, as it is also
treated as such from a morphological point of view by Stahl and others.
We now come to an enumeration of those cases in which the date of the
first appearance [612] of a new horticultural variety has been recorded,
and I must apologize for the necessity of again quoting many variations,
which have previously been dealt with from another point of view. In
such cases I shall limit myself as closely as possible to historical
facts. They have been recorded chiefly by Verlot and Carriere, who wrote
in Paris shortly after the middle of the past century, and afterwards by
Darwin, Korshinsky, and others. It is from their writings and from
horticultural literature at large that the following evidence is brought
together.
A very well-known instance is that of the dwarf variety of _Tagetes
signata_, which arose in the nursery of Vilmorin in the year 1860. It
was observed for the first time in a single individual among a lot of
the ordinary _Tagetes signata_. It was found impossible to isolate it,
but the seeds were saved separately. The majority of the offspring
returned to the parental type, but two plants were true dwarfs. From
these the requisite degree of purity for commercial purposes was
reached, the vicinists not being more numerous than 10% of the entire
number. The same mutation had been observed a year earlier in the same
nursery in a lot of _Saponaria calabrica_. The seeds of this dwarf
repeated the variety in the next generation, but in the third none were
observed. Then the variety was [613] thought to be lost, and the culture
was given up, as the Mendelian law of the splitting of varietal hybrids
was not known. According to our present knowledge we might expect the
atavistic descendants of the first dwarf to be hybrids, and to be liable
to split in their progeny into one-fourth dwarfs and three-fourths
normal specimens. From this it is obvious that the dwarfs would have
appeared a second time if the strain had been continued by means of the
seeds of the vicinistic progeny.
In order to avoid a return to this phase of the question, another use of
the vicinists should at once be pointed out. It is the possibility of
increasing the yield of the new variety. If space admits of sowing the
seeds of the vicinists, a quarter of the progeny may be expected to come
true to the new type, and if they were partly pollinated by the dwarfs,
even a larger number would do so. Hence it should be made a rule to sow
these seeds also, at least when those of the true representatives of the
novelty do not give seed enough for a rapid multiplication.
Other dwarfs are recorded to have sprung from species in the same sudden
and unexpected manner, as for instance _Ageratum coeruleum_ of the same
nursery, further _Clematis Viticella nana_ and _Acer campestre nanum_.
_Prunus Mahaleb nana_ was discovered in 1828 in one [614] specimen near
Orleans by Mme. LeBrun in a large culture of Mahaleb. _Lonicera tatarica
nana_ appeared in 1825 at Fontenay-aux Roses. A tall variety of the
strawberry is called "Giant of Zuidwijk" and originated at Boskoop in
Holland in the nursery of Mr. van de Water, in a lot of seedlings of the
ordinary strawberry. It was very large, but produced few runners, and
was propagated with much difficulty, for after six years only 15 plants
were available. It proved to be a late variety with abundant large
fruit, and was sold at a high price. For a long time it was prominent in
cultures in Holland only.
Varieties without prickles are known to have originated all of a sudden
in sundry cases. _Gleditschia sinensis_, introduced in 1774 from China,
gave two seedlings without spines in the year 1823, in the nursery of
Caumzet. It is curious in being one of the rare instances where a
simultaneous mutation in two specimens is acknowledged, because as a
rule, such records comply with the prevailing, though inexact, belief
that horticultural mutations always appear in single individuals.
From Korshinsky's survey of varieties with cut leaves or laciniate forms
the following cases may be quoted. In the year 1830 a nurseryman named
Jacques had sown a large lot of elms, [615] _Ulmus pedunculata_. One of
the seedlings had cut leaves. He multiplied it by grafting and gave it
to the trade under the name of _U. pedunculata urticaefolia_. It has
since been lost.
Laciniate alders seem to have been produced by mutation at sundry times.
Mirbel says that the _Alnus glutinosa laciniata_ is found wild in
Normandy and in the forests of Montmorency near Paris. A similar variety
has been met with in a nursery near Orleans in the year 1855. In
connection with this discovery some discussion has arisen concerning the
question whether it was probable that the Orleans strain was a new
mutation, or derived in some way from the trees cited by Mirbel. Of
course, as always in such cases, any doubt, once pronounced, affects the
importance of the observation for all time, since it is impossible to
gather sufficient historical evidence to fully decide the point. The
same variety had appeared under similar circumstances in a nursery at
Lyons previously (1812).
Laciniated maples are said to be of relatively frequent occurrence in
nurseries, among seedlings of the typical species. Loudon says that once
100 laciniated seedlings were seen to originate from seed of some normal
trees. But in this case it is rather probable that the presumed [616]
normal parents were in reality hybrids between the type and the
laciniated form, and simply split according to Mendel's law. This
hypothesis is partly founded on general considerations and partly on
experiments made by myself with the cut-leaved celandine, previously
alluded to, which I crossed with the type. The hybrids repeated the
features of the species and showed no signs of their internal hybrid
constitution. But the following year one-fourth of their progeny
returned to the cut-leaved form. If the same thing has taken place in
the case of Loudon's maples, but without their hybrid origin being
known, the result would have been precisely what he observed.
_Broussonetia papyriffera dissecta_ originated about 1830 at Lyons, and
a second time in 1866 at Fontenay-aux-Roses. The cut-leaved hazelnuts,
birches, beeches and others have mostly been found in the wild state, as
I have already pointed out in a previous lecture. A similar variety of
the elder, _Sambucus nigra laciniata_, and its near ally, _Sambucus
racemosa laciniata_, are often to be seen in our gardens. They have been
on record since 1886 and come true from seed, but their exact origin
seems to have been forgotten. Cut-leaved walnuts have been known since
1812; they come true from seed, but are extremely liable to vicinism, a
nuisance which is [617] ascribed by some authors to the fact that often
on the same tree the male catkins flower and fall off several weeks
before the ripening of the pistils of the other form of flowers.
Weeping varieties afford similar instances. _Sophora japonica pendula_
originated about 1850, and _Gleditschia triacanthos pendula_ some time
later in a nursery at Chateau-Thierry (Aisne, France). In the year 1821
the bird's cherry, or _Prunus Padus_, produced a weeping variety, and in
1847 the same mutation was observed for the allied _Prunus Mahaleb_.
Numerous other instances of the sudden origin of weeping trees, both of
conifers and of others, have been brought together in Korshinsky's
paper. This striking type of variation includes perhaps the best
examples of the whole historical evidence. As a rule they appear in
large sowings, only one, or only a few at a time. Many of them have not
been observed during their youth, but only after having been planted out
in parks and forests, since the weeping characters show only after
several years.
The monophyllous bastard-acacia originated in the same way. Its
peculiarities will be dealt with on another occasion, but the
circumstances of its birth may as well be given here. In 1855 in the
nursery of Deniau, at Brain-sur-l'Authion (Maine et Loire), it appeared
in a lot of [618] seedlings of the typical species in a single
individual. This was transplanted into the Jardin des Plantes at Paris,
where it flowered and bore seeds in 1865. It must have been partly
pollinated by the surrounding normal representatives of the species,
since the seeds yielded only one-fourth of true offspring. This
proportion, however, has varied in succeeding years. Briot remarks that
the monophyllous bastard acacia is liable to petaloid alterations of its
stamens, which deficiency may encroach upon its fertility and
accordingly upon the purity of its offspring.
Broom-like varieties often occur among trees, and some are known for
their very striking reversions by buds, as we have seen on a previous
occasion. They are ordinarily called pyramidal or fastigiate forms, and
as far as their history goes, they arise suddenly in large sowings of
the normal species. The fastigiate birch was produced in this way by
Baumann, the _Abies concolor fastigiata_ by Thibault and Keteleer at
Paris, the pyramidal cedar by Paillat, the analogous form of
_Wellingtonia_ by Otin. Other instances could easily be added, though of
course some of the most highly prized broom-like trees are so old that
nothing is known about their origin. This, for instance, is the case
with the pyramidal yew-tree, _Taxus baccata fastigiata_. [619] Others
have been found wild, as already mentioned in a former lecture.
An analogous case is afforded by the purpleleaved plums, of which the
most known form is Prunus Pissardi. It is said to be a purple variety of
_Prunus cerasifera_, and was introduced at the close of the seventies
from Persia, where it is said to have been found in Tabris. A similar
variety arose independently and unexpectedly in the nursery of Spath,
near Berlin, about 1880, but it seems to differ in some minor points
from the Persian prototype.
A white variety of _Cyclamen vernum_ made its appearance in the year
1836 in Holland. A single individual was observed for the first time
among a large lot of seedlings, in a nursery near Haarlem. It yielded a
satisfactory amount of seed, and the progeny was true to the new type.
Such plants propagate slowly, and it was only twenty-seven years later
(1863) that the bulbs were offered for sale by the Haarlem firm of
Krelage & Son. The price of each bulb was $5.00 in that year, but soon
afterwards was reduced to $1.00 each, which was about thrice the
ordinary price of the red variety.
The firm of Messrs. Krelage & Son has brought into commerce a wide range
of new bulb-varieties, all due to occasional mutations, some by seed and
others by buds, or to the accidental [620] transference of new qualities
into the already existing varieties by cross-pollination through the
agency of insects. Instead of giving long lists of these novelties, I
may cite the black tulips, which cost during the first few years of
their introduction about $25.00 apiece.
Horticultural mutations are as a rule very rare, especially in genera or
species which have not yet been brought to a high degree of variability.
In these the wide range of varieties and the large scale in which they
are multiplied of course give a greater chance for new varieties. But
then the possibilities of crossing are likewise much larger, and
apparent changes due to this cause may easily be taken for original
mutations.
The rarity of the mutations is often proved by the lapse of time between
the introduction of a species and its first sport. Some instances may be
given. They afford a proof of the length of the period during which the
species remained unaltered, although some of these alterations may be
due to a cross with an allied form. _Erythrina Crista-galli_ was
introduced about 1770, and produced its first sport in 1884, after more
than a century of cultivation. _Begonia semperflorens_ has been
cultivated since 1829, and for half a century before it commenced
sporting. The same length of time has elapsed [621] between the first
culture and the first variation of _Crambe maritima_. Other cases are on
record in which the variability exhibited itself much sooner, perhaps
within a few years after the original discovery of the species. But such
instances seem, as a rule, to be subject to doubt as to the concurrence
of hybridization. So for instance the _Iris lortetii_, introduced in the
year 1895 from the Lebanon, which produced a white variety from its very
first seeds. If by chance the introduced plants were natural hybrids
between the species and the white variety, this apparent and rather
improbable mutation would find a very simple explanation. The length of
the period preceding the first signs of variability is largely, of
course, due to divergent methods of culture. Such species as
_Erythrina_, which are perennial and only sown on a small scale, should
not be expected to show varieties very soon. Annual species, which are
cultivated yearly in thousands or even hundreds of thousands of
individuals, have a much better chance. Perhaps the observed differences
are largely due to this cause.
Monstrosities have, from time to time, given rise to cultivated races.
The cockscomb or _Celosia_ is one of the most notorious instances.
Cauliflowers, turnips and varieties of cabbages are recorded by De
Candolle to have arisen in [622] culture, more than a century ago, as
isolated monstrous individuals. They come true from seed, but show
deviations from time to time which seem to be intimately linked with
their abnormal characters. Apetalous flowers may be considered as
another form of monstrosity, and in _Salpiglossis sinuata_ such a
variety without a corolla made its appearance in the year 1892 in the
nursery of Vilmorin. It appeared suddenly, yielded a good crop of seed
and was constant from the outset, without any sign of vicinism or
impurity.
In several cases the origin of a variety is obscure, while the
subsequent historical evidence is such as to make an original sudden
appearance quite probable. Although these instances offer but indirect
evidence, and will sooner or later lose their importance, it seems
desirable to lay some stress on them here, because most of these cases
are very obvious and more striking than purely historical facts. Sterile
varieties belong to this heading. Sometimes they bear fruit without
kernels, sometimes flowers without sexual organs, or even no flowers at
all. Instances have been given in the lecture on retrograde varieties;
they are ordinarily assumed to have originated by a leap, because it is
not quite clear how a loss of the capacity for the formation of seeds
could have been slowly accumulated [623] in preceding generations. An
interesting case is afforded by a sterile variety of corn, which
originated some time ago in my own pedigree-cultures made for another
purpose, and which had begun with an ear of 1886. The first generation
from the original seeds showed nothing particular, but the second at
once produced quite a number of sterile plants. The sterility was caused
by the total lack of branches, including those bearing the pistillate
flowers. The terminal spikes themselves were reduced to naked spindles,
without branches, without flowers and even almost without bracts.
In some individuals, however, this negative character was seen to give
way at the tip, showing a few small naked branches. Of course it was
impossible to propagate this curious form, but my observations showed
that it sprang into existence from known ancestors by a single step or
sudden leap. This leap, however, was not confined to a single specimen;
on the contrary it affected 40 plants out of a culture of 340
individuals. The same phenomenon was repeated from the seeds of the
normal plants in the following year, but afterwards the monstrosity
disappeared.
The Italian poplar affords another instance. It is considered by some
authors as a distinct species, _Populus italica_, and by others as a
[624] broom-like variety of the _Populus nigra_, from which it is
distinguished by its erect branches and other characters of minor
importance. It is often called the pyramidal or fastigiate poplar. Its
origin is absolutely unknown and it occurs only in the cultivated state.
In Italy it seems to have been cultivated from the earliest historical
times, but it was not introduced into other countries till the
eighteenth century. In 1749 it was brought into France, and in 1758 into
England, and to day it may be seen along roads throughout central Europe
and in a large part of Asia. But the most curious fact is that it is
only observed in staminate specimens; pistillate trees have not been
found, although often sought for. This circumstance makes it very
probable that the origin of the broom-like poplar was a sudden mutation,
producing only one individual. This being staminate, it has been
propagated exclusively by cuttings. It is to be admitted, however, that
no material evidence is at hand to prove that it is not an original wild
species, the pistillate form of which has been lost by vegetative
multiplication. One form only of many dioecious plants is to be found in
cultivation, as, for instance some South American species of _Ribes_.
Total lack of historical evidence concerning [625] the origin of a
variety has sometimes been considered as sufficient proof of a sudden
origin. The best known instance is that of the renowned cactus-dahlia
with its recurved instead of incurved ray-florets. It was introduced
from Mexico into the Netherlands by Van den Berg of Jutphaas, under the
following remarkable circumstances. In the autumn of 1872 one of his
friends had sent him a small case, containing seeds, bulbs and roots
from Mexico. From one of these roots a _Dahlia_ shoot developed. It was
cultivated with great care and bloomed next year. It surprised all who
saw it by the unexpected peculiarity of its large rich crimson flowers,
the rays of which were reversed tubular. The margins of the narrow rays
were curved backwards, showing the bright color of the upper surface. It
was a very showy novelty, rapidly multiplied by cuttings, and was soon
introduced into commerce. It has since been crossed with nearly all
other available varieties of the _Dahlia_, giving a large and rich group
of forms, bound together by the curious curling of the petals. It has
never been observed to grow in Mexico, either wild or in gardens, and
thus the introduced individual has come to be considered as the first of
its race.
I have already mentioned that the rapid production of large numbers of
new varieties, by [626] means of the crossing of the offspring of a
single mutant with previously existing sorts, is a very common feature
in horticultural practice. It warns us that only a small part of the
novelties introduced yearly are due to real mutations. Further instances
of novelties with such a common origin are the purple-leaved dahlias,
the gooseberries without prickles, the double petunias, erect gloxinias
and many others. Accumulation of characters, acquired in different races
of a species, may easily be effected in this way; in fact it is one of
the important factors in the breeding of horticultural novelties.
I have alluded more than once in this lecture to the question, whether
it is probable that mutations occur in one individual or in more. The
common belief among horticulturists is that, as a rule, they appear in a
single plant. This belief is so widespread that whenever a novelty is
seen for the first time in two or more specimens it is at once suggested
that it might have originated and been overlooked in a previous
generation. Not caring to confess a lack of close observation, the
number of mutants in such cases is usually kept secret. At least this
statement has been made to me by some of the horticulturists at Erfurt,
whom I visited some years ago in order to learn as much as [627]
possible about the methods of production of their novelties. Hence it is
simply impossible to decide the question on the basis of the experience
of the breeders. Even in the case of the same novelty arising in sundry
varieties of the same species, the question as to common origin, by
means of crossing, is often hard to decide, as for instance in
moss-roses and nectarines. On the other hand, instances are on record
where the same novelty has appeared at different times, often at long
intervals. Such is the case with the butterfly-cyclamen, a form with
wide-spreading petals which originated in Martin's nursery in England.
The first time it was seen it was thought to be of no value, and was
thrown away, but when appearing for a second time it was multiplied and
eventually placed on the market. Other varieties of _Cyclamen_, as for
instance the crested forms, are also known to have originated
repeatedly.
In concluding this series of examples of horticultural mutations, I
might mention two cases, which have occurred in my own experimental
garden. The first refers to a tubular _Dahlia_. It has ray-florets, the
ligules of which have their margins grown together so as to form tubes,
with the outer surface corresponding to the pale under-surface of the
corolla.
This novelty originated in a single plant in a [628] culture from the
seed of the dwarf variety "Jules Chretien." The seeds were taken from
introduced plants in my garden, and as the sport has no ornamental value
it is uncertain whether this was the first instance or whether it had
previously occurred in the nursery at Lyons, from whence the bulbs were
secured. Afterwards it proved true from seed, but was very variable,
exhibiting rather the features of an ever-sporting variety.
Another novelty was seen the first time in several individuals. It was a
pink sport of the European cranesbill, _Geranium pratense_. It arose
quite unexpectedly in the summer of 1902 from a striped variety of the
blue species. It was seen in seven specimens out of a lot of about a
hundred plants. This strain was introduced into my garden in 1897, when
I bought two plants under the name of _Geranium pratense album_, which
however proved to belong to the striped variety. From their seeds I
sowed in 1898 a first generation, of which a hundred plants flowered the
next year, and from their seeds I sowed in 1900 the lot which produced
the sport. Neither the introduced plants nor their offspring had
exhibited the least sign of a color-variation, besides the blue and
white stripes. Hence it is very probable that my novelty was a true
first mutation, the more probably [629] so since a pink variety would
without doubt have a certain horticultural value and would have been
preserved if it had occurred. But as far as I have been able to
ascertain, it is as yet unknown, nor has it been described until today.
Summing up the results of this long, though very incomplete, list of
horticultural novelties with a more or less well-known origin, we see
that sudden appearances are the rule. Having once sprung into existence
the new varieties are ordinarily constant, except as affected by
vicinism. Details concerning the process are mostly unavailable or at
least are of very doubtful value. And to this it should be added that
really progressive mutations have hardly been observed in horticulture.
Hence the theoretical value of the facts is far less than might have
been expected.
[630]
LECTURE XXII