MONSTROSITIES_Species and Varieties, Their Origin by Mutation

I have previously dealt with the question of the hereditary tendencies

that cause monstrosities. These tendencies are not always identical for

the same anomaly. Two different types may generally, be distinguished.

One of them constitutes a poor variety, the other a rich one. But this

latter is abundant and the first one is poor in instances of exactly the

same conformation. Therefore the difference only lies in the frequency

of the anomaly, and not in its visible features. In discovering an

instance of any anomaly it is therefore impossible to tell whether it

belongs to a poor or to a rich race. This important question can only be

answered by direct sowing-experiments to determine the degree of

heredity.

Monstrosities are often considered as accidents, and rightfully so, at

least as long as they are considered from a morphological point of view.

Physiology of course excludes all accidentality. And in our present ease

it shows [401] that some internal hereditary quality is present, though

often latent, and that the observed anomalies are to be regarded as

responses of this innate tendency to external conditions. Our two types

differ in the frequency of these responses. Rare in the poor race, they

are numerous in the rich variety. The external conditions being the same

for both, the hereditary factor must be different. The tendency is weak

in the one and strong in the other. In both cases, according to my

experience, it may be weakened or strengthened by selection and by

treatment. Often to a very remarkable degree, but not so far as to

transgress the limits between the two races. Such transgression may

apparently be met with from time to time, but then the next generation

generally shows the fallacy of the conclusion, as it returns more or

less directly to the type from which the strain had been derived.

Monstrosities should always be studied by physiologists from this point

of view. Poor and rich strains of the same anomaly seem at first sight

to be so nearly allied that it might be thought to be very easy to

change the one into the other. Nevertheless such changes are not on

record, and although I have made several attempts in this line, I never

succeeded in passing the limit. I am quite convinced that sometime [402]

a method will be discovered of arbitrarily producing such conversions,

and perhaps the easiest way to attain artificial mutations may lie

concealed here. But as yet not the slightest indication of this

possibility is to be found, save the fallacious conclusions drawn from

too superficial observations.

Unfortunately the poor strains are not very interesting. Their chance of

producing beautiful instances of the anomaly for which they are

cultivated is too small. Exceptions to this rule are only afforded by

those curious and rare anomalies, which command general attention, and

of which, therefore, instances are always welcome. In such cases they

are searched for with perseverance, and the fact of their rarity

impresses itself strongly on our mind.

Twisted stems are selected as a first example. This monstrosity, called

_biastrepsis_, consists of strongly marked torsions as are seen in many

species with decussate leaves, though as a rule it is very rare. Two

instances are the most generally known, those of the wild valerian

(_Valeriana officinalis_) and those of cultivated and wild sorts of

teasels (_Dipsacus fullonum_, _D. sylvestris_, and others). Both of

these I have cultivated during upwards of fifteen years, but with

contradictory results. The valerian is a perennial herb, multiplying

itself yearly by [403] slender rootstocks or runners producing at their

tips new rosettes of leaves and in the center of these the flowering

stem. My original plant has since been propagated in this manner, and

during several years I preserved large beds with hundreds of stems, in

others I was compelled to keep my culture within more restricted limits.

This plant has produced twisted stems of the curious shape, with a

nearly straight flag of leaves on one side, described by De Candolle and

other observers, nearly every year. But only one or two instances of

abnormal stems occurred in each year, and no treatment has been found

that proved adequate to increase this number in any appreciable manner.

I have sown the seeds of this plant repeatedly, either from normal or

from twisted stems, but without better results. It was highly desirable

to be able to offer instances of this rare and interesting peculiarity

to other universities and museums, but no improvement of the race could

be reached and I have been constrained to give it up. My twisted

valerian is a poor race, and hardly anything can be done with it.

Perhaps, in other countries the corresponding rich race may be hidden

somewhere, but I have never had the good fortune of finding it.

This good fortune however, I did have with the wild teasel or _Dipsacus

sylvestris_. [404] Stems of this and of allied species are often met

with and have been described by several writers, but they were always

considered as accidents and nobody had ever tried to cultivate them. In

the summer of 1885 I saw among a lot of normal wild teasels, two nicely

twisted stems in the botanical garden of Amsterdam. I at once proposed

to ascertain whether they would yield a hereditary race and had all the

normal individuals thrown away before the flowering time. My two plants

flowered in this isolated condition and were richly pollinated by

insects. Of course, at that time, I knew nothing of the dependency of

monstrosities on external conditions, and made the mistake of sowing the

seeds and cultivating the next generation in too great numbers on a

small space. But nevertheless the anomaly was repeated, and the aberrant

individuals were once more isolated before flowering. The third

generation repeated the second, but produced sixty twisted stems on some

1,600 individuals. The result was very striking and quite sufficient for

all further researches, but the normal condition of the race was not

reached. This was the case only after I had discovered the bad effects

of growing too many plants in a limited space. In the fourth generation

I restricted my whole culture to about 100 individuals, and by this

simple [405] means at once got up to 34% of twisted stems. This

proportion has since remained practically the same. I have selected and

isolated my plants during five succeeding generations, but without any

further result, the percentage of twisted stems fluctuating between 30

and about 45 according to the size of the cultures and the favorableness

or unfavorableness of the weather.

It is very interesting to note that all depends on the question whether

one has the good fortune of finding a rich race or not, as this

pedigree-culture shows. Afterwards everything depends on treatment and

very little on selection. As soon as the treatment becomes adequate, the

full strength of the race at once displays itself, but afterwards no

selection is able to improve it to any appreciable amount. Of course, in

the long run, the responses will be the same as those of the pistilloid

poppies on the average, and some influence of selection will show itself

on closer scrutiny.

Compared with the polycephalous poppies my race of twisted teasels is

much richer in atavists. They are never absent, and always constitute a

large part of each generation and each bed, comprising somewhat more

than half of the individuals. Intermediate stages between them and the

wholly twisted stems are not wanting, [406] and a whole series of steps

may easily be observed from sufficiently large cultures. But they are

always relatively rare, and any lot of plants conveys the idea of a

dimorphous race, the small twisted stems contrasting strongly with the

tall straight ones.

A sharper contrast between good representatives of a race and their

atavists is perhaps to be seen in no other instance. All the details

contribute to the differentiation in appearance. The whole stature of

the plants is affected by the varietal mark. The atavists are not, as in

the case of the poppies, obviously allied with the type by a full range

of intermediate steps, but quite distant from it by their rarity. There

seems to be a gap in the same way as between the striped flowers of the

snapdragon and their uniform red atavists, while with the poppies the

atavists may be viewed as being only the extremes of a series of

variations fluctuating around some average type.

From this reason it is as interesting to appreciate the hereditary

position of the atavists of twisted varieties as it was for the

red-flowered descendants of the striped flowers. In order to ascertain

this relation it is only necessary to isolate some of them during the

blooming-period. I made this experiment in the summer of 1900 with the

eighth generation of my race, and contrived [407] to isolate three

groups of plants by the use of parchment bags, covering them

alternately, so the flowers of only one group were accessible to

insects, at a time. I made three groups, because the atavists show two

different types. Some specimens have decussate stems, others bear all

their leaves in whorls of three, but in respect to the hereditary

tendency of the twisting character this difference does not seem to be

of any importance.

In this way I got three lots of seeds and sowed enough of them to have

three groups of plants each containing about 150-200 well developed

stems. Among these I counted the twisted individuals, and found nearly

the same numbers for all three. The twisted parents gave as many as 41%

twisted children, but the decussate atavists gave even somewhat more,

viz., 44%, while the ternate specimens gave 37%. Obviously the

divergences between these figures are too slight to be dwelt upon, but

the fact that the atavists are as true or nearly as true inheritors of

the twisted race as the best selected individuals is clearly proved by

this experience.

It is evident that here we have a double race, including two types,

which may be combined in different degrees. These combinations determine

a wide range of changes in the stature of the plants, and it seems

hardly right to use the [408] same term for such changes as for common

variations. It is more a contention of opposite characters than a true

phenomenon of simple variability. Or perhaps we might say that it is the

effect of the cooperation of a very variable mark, the twisting, with a

scarcely varying attribute of the normal structure of the stem. Between

the two types an endless diversity prevails, but outwardly there are

limits which are never transgressed. The double race is as permanent,

and in this sense as constant, as any ordinary simple variety, both in

external form, and in its intimate hereditary qualities.

I have succeeded in discovering some other rich races of twisted plants.

One of them is the Sweet William (_Dianthus barbatus_), which yielded,

after isolation, in the second generation, 25% of individuals with

twisted stems, and as each individual produces often 10 and more stems,

I had a harvest of more than half a thousand of instances of this

curious, and ordinarily very rare anomaly. My other race is a twisted

variety of _Viscaria oculata_, which is still in cultivation, as it has

the very consistent quality of being an annual. It yielded last summer

(1903) as high a percentage as 65 of twisted individuals, many of them

repeating the monstrosity on several branches. After some occasional

observations _Gypsophila paniculata_ [409] seems to promise similar

results. On the other hand I have sowed in vain the seeds of twisted

specimens of the soapwort and the cleavewort (_Saponaria officinalis_

and _Galium Aparine_). These and some others seem to belong to the same

group as the valerian and to constitute only poor or so-called

half-races.

Next to the torsions come the fasciated stems. This is one of the most

common of all malformations, and consists, in its ordinary form, of a

flat ribbon-like expansion of the stems or branches. Below they are

cylindrical, but they gradually lose this form and assume a flattened

condition. Sometimes the rate of growth is unequal on different portions

or on the opposite sides of the ribbon, and curvatures are produced and

these often give to the fasciation a form that might be compared with a

shepherd's crook. It is a common thing for fasciated branches and stems

to divide at the summit into a number of subdivisions, and ordinarily

this splitting occurs in the lower part, sometimes dividing the entire

fasciated portion. In biennial species the rosette of the root-leaves of

the first year may become changed by the monstrosity, the heart

stretching in a transverse direction so as to become linear. In the next

year this line becomes the base from which the stem grows. In such cases

the fasciated stems [410] are broadened and flattened from the very

beginning, and often retain the incipient breadth throughout their

further development. Species of primroses (_Primula japonica_ and

others), of buttercups (_Ranunculus bulbosus_), the rough hawksbeard

(_Crepis biennis_), the Aster _Tripolium_, and many others could be

given as instances.

Some of these are so rare as to be considered as poor races, and in

cultural trials do not produce the anomaly except in a very few

instances. Heads of rye are found in a cleft condition from time to

time, single at their base and double at the top, but this anomaly is

only exceptionally repeated from seed. Flattened stems of _Rubia

tinctorum_ are not unfrequently met with on the fields, but they seem to

have as little hereditary tendency as the split rye (_Secale Cereale_).

Many other instances could be given. Both in the native localities and

in pedigree-cultures such ribboned stems are only seen from time to

time, in successive years, in annual and biennial as well as in

perennial species. The purple pedicularis (_Pedicularis palustris_) in

the wild state, and the sunflower among cultivated plants, may be cited

instead of giving a long list of analogous instances.

On the other hand rich races of flattened stems are not entirely

lacking. They easily betray [411] themselves by the frequency of the

anomaly, and therefore may be found, and tried in the garden. Under

adequate cultivation they are here as rich in aberrant individuals as

the twisted races quoted above, producing in good years from 30-40% and

often more instances. I have cultivated such rich races of the dandelion

(_Taraxacum officinale_), of _Thrincia hirta_, of the dame's violet

(_Hesperis matronalis_), of the hawkweed (_Picris hieracioides_), of the

rough hawksbeard (_Crepis biennis_), and others.

Respecting the hereditary tendencies these rich varieties with flattened

stems may be put in the same category with the twisted races. Two points

however, seem to be of especial interest and to deserve a separate

treatment.

The common cockscomb or _Celosia cristata_, one of the oldest and most

widely cultivated fasciated varieties may be used to illustrate the

first point. In beds it is often to be seen in quite uniform lots of

large and beautiful crests, but this uniformity is only secured by

careful culture and selection of the best individuals. In experimental

trials such selection must be avoided, and in doing so a wide range of

variability at once shows itself. Tall, branched stems with fan-shaped

tops arise, constituting a series of steps towards complete atavism.

This last [412] however, is not to be reached easily. It often requires

several successive generations grown from seed collected from the most

atavistic specimens. And even such selected strains are always reverting

to the crested type. There is no transgression, no springing over into a

purely atavistic form, such as may be supposed to have once been the

ancestor of the present cockscomb. The variety includes crests and

atavists, and may be perpetuated from both. Obviously every gardener

would select the seeds of the brightest crests, but with care the full

crests may be recovered, even from the worst reversionists in two or

three generations. It is a double race of quite the same constitution as

the twisted teasels.

My second point is a direct proof of this assertion, but made with a

fasciated variety of a wild species. I took for my experiment the rough

hawksbeard. In the summer of 1895 I isolated some atavists of the fifth

generation of my race, which, by ordinary selection, gave in the average

from 20-40% of fasciated stems. My isolated atavists bore abundant

fruit, and from these I had the next year a set of some 350 plants, out

of which about 20% had broadened and linear rosettes. This proportion

corresponds with the degree of inheritance which is shown in many years

by the largest and strongest [413] fasciated stems. It strengthens our

conclusion as to the innermost constitution of the double races or

ever-sporting varieties.

Twisted stems and fasciations are very striking monstrosities. But they

are not very good for further investigation. They require too much space

and too much care. The calculation of a single percentage requires the

counting of some hundreds of individuals, taking many square meters for

their cultivation, and this, as my best races are biennial, during two

years. For this reason the countings must always be very limited, and

selection is restrained to the most perfect specimens.

Now the question arises, whether this mark is the best upon which to

found selection. This seems to be quite doubtful. In the experiments on

the heredity of the atavists, we have seen that they are, at least

often, in no manner inferior to even the best inheritors of the race.

This suggests the idea that it is not at all certain that the visible

characters of a given individual are a trustworthy measure of its value

as to the transmission of the same character to the offspring. In other

words, we are confronted with the existence of two widely different

groups of characters in estimating the hereditary tendency. One is the

visible quality of the individuals and the other is the direct

observation [414] of the degree in which the attribute is transmitted.

These are by no means parallel, and seem in some sense to be nearly

independent of each other. The fact that the worst atavists may have the

highest percentage of varietal units seems to leave no room for another

explanation.

Developing this line of thought, we gradually arrive at the conclusion

that the visible attribute of a varying individual is perhaps the most

untrustworthy and the most unreliable character for selection, even if

it seems in many cases practically to be the only available one. The

direct determination of the degree of heredity itself is obviously

preferable by far. This degree is expressed by the proportion of its

inheritors among the offspring, and this figure therefore should be

elevated to the highest rank, as a measure of the hereditary qualities.

Henceforward we will designate it by the name of hereditary percentage.

In scientific experiments this figure must be determined for every plant

of a pedigree-culture singly, and the selection should be founded

exclusively or at least mainly on it. It is easily seen that this method

requires large numbers of individuals to be grown and counted. Some two

or three hundred progeny of one plant are needed to give the decisive

figure for this one [415] individual, and selection requires the

comparison of at least fifty or more individuals. This brings the total

amount of specimens to be counted up to some tens of thousands. In

practice, where important interests depend upon the experiments, such

numbers are usually employed and often exceeded, but for the culture of

monstrosities, other methods are to be sought in order to avoid these

difficulties.

The idea suggests itself here that the younger the plants are, when

showing their distinguishing marks, the more of them may be grown on a

small space. Hence the best way is to choose such attributes, as may

already be seen in the young seedlings, in the very first few weeks of

their lives. Fortunately the seed-leaves themselves afford such

distinctive marks, and by this means the plants may be counted in the

pans, requiring no culture at all in the garden. Only the selected

individuals need be grown to ripen their seeds, and the whole selection

may be made in the spring, in the glasshouse. Instead of being very

troublesome, the determination of the hereditary percentages becomes a

definite reduction of the size of the experiments. Moreover it may

easily be effected by any one who cares for experimental studies, but

has not the means required for cultures on a larger scale. And lastly,

there are [416] a number of questions about heredity, periodicity,

dependency on nourishment and other life conditions, and even about

hybridizing, which may be answered by this new method.

Seed-leaves show many deviations from the ordinary shape, especially in

dicotyledonous plants. A very common aberration is the multiplication of

their number, and three seed-leaves in a whorl are not rarely met with.

The whorl may even consist of four, and in rare cases of five or more

cotyledons. Cleft cotyledons are also to be met with, and the fissure

may extend varying distances from the tips. Often all these deviations

may be seen among the seedlings of one lot, and then it is obvious that

together they constitute a scale of cleavages, the ternate and

quaternate whorls being only cases where the cleaving has reached its

greatest development. All in all it is manifest that here we are met by

one type of monstrosity, but that this type allows of a wide range of

fluctuating variability. For brevity's sake all these cleft and ternate,

double cleft and quaternate cotyledons and even the higher grades are

combined under one common name and indicated as tricotyls.

A second aberration of young seed-plants is exactly opposite to this. It

consists of the union of the two seed-leaves into a single organ. This

ordinarily betrays its origin by [417] having two separate apices, but

not always. Such seedlings are called syncotyledonous or syncotyls.

Other monstrosities have been observed from time to time, but need not

be mentioned here.

It is evident that the determination of the hereditary percentage is

very easy in tricotylous or syncotylous cultures. The parent plants must

be carefully isolated while blooming. Many species pollinate themselves

in the absence of bees; from these the insects are to be excluded.

Others have the stamens and stigmas widely separated and have to be

pollinated artificially. Still others do not lend themselves to such

operations, but have to be left free to the visits of bees and of

humble-bees, this being the only means of securing seed from every

plant. At the time of the harvest the seeds should be gathered

separately from each plant, and this precaution should also be observed

in studies of the hereditary percentage at large, and in all scientific

pedigree-cultures. Every lot of seeds is to be sown in a separate pan,

and care must be taken to sow such quantities the three to four hundred

seedlings will arise from each. As soon as they display their

cotyledons, they are counted, and the number is the criterion of the

parent-plant. Only parent-plants with the highest percentages are

selected, and out of [418] their seedlings some fifty or a hundred of

the best ones are chosen to furnish the seeds for the next generation.

This description of the method shows that the selection is a double one.

The first feature is the hereditary percentage. But then not all the

seedlings of the selected parents can be planted out, and a choice has

to be made. This second selection may favor the finest tricotyls, or the

strongest individuals, or rely on some other character, but is

unavoidable.

We now come to the description of the cultures. Starting points are the

stray tricotyls which are occasionally found in ordinary sowings. In

order to increase the chance of finding them, thousands of seeds of the

same species must be inspected, and the range of species must be widened

as much as possible.

Material for beginning such experiments is easily obtained, and almost

any large sample of seeds will be found suitable. Some tricotyls will be

found among every thousand seedlings in many species, while in others

ten or a hundred times, as many plants must be examined to secure them,

but species with absolutely pure dicotylous seeds are very rare.

The second phase of the experiment, however, is not so promising. Some

species are rich, and others are poor in this anomaly. This difference

[419] often indicates what can be expected from further culture. Stray

tricotyls point to poor species or half-races, while more frequent

deviations suggest rich or double-races. In both cases however, the

trial must be made, and this requires the isolation of the aberrant

individuals and the determination of their hereditary percentage.

In some instances the degree of their inheritance is only a very small

one. The isolated tricotyls yield 1 or 2% of inheritors, in some cases

even less, or upwards up to 3 or 4%. If the experiment is repeated, no

amelioration is observed, and this result remains the same during a

series of successive generations. In the case of _Polygonum

convolvulus_, the Black bindweed, I have tried as many as six

generations without ever obtaining more than 3%. With other species I

have limited myself to four successive years with the same negative

result, as with spinage, the Moldavian dragon-head, (_Dracocephalum

moldavicum_), and two species of corn catch-fly (_Silene conica_ and _S.

conoidea_).

Such poor races hardly afford a desirable material for further

inquiries. Happily the rich races, though rare, may be discovered also

from time to time. They seem to be more common among cultivated plants

and horticultural as well as agricultural species may be used. Hemp

[420] and mercury (_Mercurialis annua_) among the first, snapdragon,

poppies, _Phacelia_, _Helichrysum_, and _Clarkia_ among garden-flowers

may be given as instances of species containing the rich tricotylous

double races.

It is very interesting to note how strong the difference is between such

cases and those which only yield poor races. The rich type at once

betrays itself. No repeated selection is required. The stray tricotyls

themselves, that are sought out from among the original samples, give

hereditary percentages of a much higher type after isolation than those

quoted above. They come up to 10-20% and in some cases even to 40%. As

may be expected, individual differences occur, and it must even be

supposed that some of the original tricotyls may not be pure, but

hybrids between tricotylous and dicotylous parents. These are at once

eliminated by selection, and if only the tricotyls which have the

highest percentages are chosen for the continuance of the new race, the

second generation comes up with equal numbers of dicotyls and tricotyls

among the seedlings. The figures have been observed to range from 51-58%

in the majority of the cases, and average 55%, rarely diverging somewhat