Chapter 30

[527] The _laevifolia_, or smooth-leaved variety, was one of the very first deviating types found in the original field. This was in the summer of 1887, seventeen years ago. It formed a little group of plants growing at some distance from the main body, in the same field. I found some rosettes and some flowering stems and sowed some seed in the fall. The variety has been quite constant in the field, neither increasing in number of individual plants nor changing its place, though now closely surrounded by other _Lamarckiana_s. In my garden it has proved to be constant from seed, never reverting to the original _lamarckiana_, provided intercrossing was excluded.

It is chiefly distinguished from Lamarck's evening-primrose by its smooth leaves, as the name indicates. The leaves of the original form show numerous sinuosities in their blades, not at the edge, but anywhere between the veins. The blade shows numbers of convexities on either surface, the whole surface being undulated in this manner; it lacks also the brightness of the ordinary evening-primrose or _Oenothera biennis_.

These undulations are lacking or at least very rare on the leaves of the new _laevifolia_. Ordinarily they are wholly wanting, but at times single leaves with slight manifestations of this [528] character may make their appearance. They warn us that the capacity for such sinuosities is not wholly lost, but only lies dormant in the new variety. It is reduced to a latent state, exactly as are the apparently lost characters of so many ordinary horticultural varieties.

Lacking the undulations, the _laevifolia_ leaves are smooth and bright. They are a little narrower and more slender than those of the _lamarckiana_. The convexities and concavities of leaves are said to be useful in dry seasons, but during wet summers, such as those of the last few years, they must be considered as very harmful, as they retain some of the water which falls on the plants, prolonging the action of the water on the leaves. This is considered by some writers to be of some utility after slight showers, but was observed to be a source of weakness during wet weather in my garden, preventing the leaves from drying. Whether the _laevifolia_ would do better under such circumstances, remains to be tested.

The flowers of the _laevifolia_ are also in a slight degree different from those of _lamarckiana_. The yellow color is paler and the petals are smoother. Later, in the fall, on the weaker side branches these differences increase. The _laevifolia_ petals become smaller and are often not emarginated at the apex, becoming ovate [529] instead of obcordate. This shape is often the most easily recognized and most striking mark of the variety. In respect to the reproductive organs, the fertility and abundance of good seed, the _laevifolia_ is by no means inferior or superior to the original species.

_O. brevistylis_, or the short-styled evening primrose, is the most curious of all my new forms. It has very short styles, which bring the stigmas only up to the throat of the calyx tube, instead of upwards of the anthers. The stigmas themselves are of a different shape, more flattened and not cylindrical. The pollen falls from the anthers abundantly on them, and germinates in the ordinary manner.

The ovary which in _lamarckiana_ and in all other new forms is wholly underneath the calyx-tube, is here only partially so. This tube is inserted at some distance under its summit. The insertion divides the ovary into two parts: an upper and a lower one. The upper part is much reduced in breadth and somewhat attenuated, simulating a prolongation of the base of the style. The lower part is also reduced, but in another manner. At the time of flowering it is like the ovary of _lamarckiana_, neither smaller nor larger. But it is reached by only a very few pollen-tubes, and is therefore always incompletely fertilized. It does [530] not fall off after the fading away of the flower, as unfertilized ovaries usually do; neither does it grow out, nor assume the upright position of normal capsules. It is checked in its development, and at the time of ripening it is nearly of the same length as in the beginning. Many of them contain no good seeds at all; from others I have succeeded in saving only a hundred seeds from thousands of capsules.

These seeds, if purely pollinated, and with the exclusion of the visits of insects, reproduce the variety, entirely and without any reversion to the _lamarckiana_ type.

Correlated with the detailed structures is the form of the flower-buds. They lack the high stigma placed above the anthers, which in the _lamarckiana_, by the vigorous growth of the style, extends the calyx and renders the flower bud thinner and more slender. Those of the _brevistylis_ are therefore broader and more swollen. It is quite easy to distinguish the individuals by this striking character alone, although it differs from the parent in other particulars.

The leaves of the _O. brevistylis_ are more rounded at the tip, but the difference is only pronounced at times, slightly in the adult rosettes, but more clearly on the growing summits of the stems and branches. By this character, the plants [531] may be discerned among the others, some weeks before the flowers begin to show themselves. But the character by which the plants may be most easily recognized from a distance in the field is the failure of the fruits. They were found there nearly every year in varying, but always small numbers.

Leaving the short-styled primrose, we come now to the last of our group of retrograde varieties. This is the _O. nanella_, or the dwarf, and is a most attractive little plant. It is very short of stature, reaching often a height of only 20-30 cm., or less than one-fourth of that of the parent. It commences flowering at a height of 10-15 cm., while the parent-form often measures nearly a meter at this stage of its development. Being so very dwarfed the large flowers are all the more striking. They are hardly inferior to those of the _lamarckiana_, and agree with them in structure. When they fade away the spike is rapidly lengthened, and often becomes much longer than the lower or vegetative part of the stem.

The dwarfs are one of the most common mutations in my garden, and were observed in the native locality and also grown from seeds saved there. Once produced they are absolutely constant. I have tried many thousands of seeds from various dwarf mutants, and never observed [532] any trace of reversion to the _lamarckiana_ type. I have also cultivated them in successive generations with the same result. In a former lecture we have seen that contrary to the general run of horticultural belief, varieties are as constant as the best species, if kept free from hybrid admixtures. This is a general rule, and the exceptions, or cases of atavism are extremely rare. In this respect it is of great interest to observe that this constancy is not an acquired quality, but is to be considered as innate, because it is already fully developed at the very moment when the original mutation takes place.

From its first leaves to the rosette period, and through this to the lengthening of the stem, the dwarfs are easily distinguished from any other of their congeners. The most remarkable feature is the shape of the leaves. They are broader and shorter, and especially at the base they are broadened in such a way as to become apparently sessile. The stalk is very brittle, and any rough treatment may cause the leaves to break off. The young seedlings are recognizable by the shape of the first two or three leaves, and when more of them are produced, the rosettes become dense and strikingly different from others. Later leaves are more nearly like the parent-type, but the petioles remain short. The bases of the blades are frequently [533] almost cordate, the laminae themselves varying from oblong-ovate to ovate in outline. The stems are often quite unbranched, or branched only at the base of the spike. Strong secondary stems are a striking attribute of the _lamarckiana_ parent, but they are lacking, or almost so in the dwarfs. The stem is straight and short, and this, combined with the large crown of bright flowers, makes the dwarfs eminently suitable for bed or border plants. Unfortunately they are very sensitive, especially to wet weather.

_Oenothera gigas_ and _O. rubrinervis_, or the giant, and the red-veined evening-primroses, are the names given to two robust and stout species, which seem to be equal in vigor to the parent-plant, while diverging from it in striking characters. Both are true elementary species, differentiated from _lamarckiana_ in nearly all their organs and qualities, but not showing any preponderating character of a retrograde nature. Their differences may be compared with those of the elementary species of other genera, as for instance, of _Draba_, or of violets, as will be seen by their description.

The giant evening-primrose, though not taller in stature than _O. lamarckiana_, deserves its name because it is so much stouter in all respects. [534] The stems are robust, often with twice the diameter of _lamarckiana_ throughout. The internodes are shorter, and the leaves more numerous, covering the stems with a denser foliage. This shortness of the internodes extends itself to the spike, and for this reason the flowers and fruits grow closer together than on the parent-plant. Hence the crown of bright flowers, opening each evening, is more dense and more strikingly brilliant, so much the more so as the individual flowers are markedly larger than those of the parents. In connection with these characters, the flower-buds are seen to be much stouter than those of _lamarckiana_. The fruits attain only half the normal size, but are broader and contain fewer, but larger seeds.

The _rubrinervis_ is in many respects a counterpart to the _gigasv, but its stature is more slender. The spikes and flowers are those of the _lamarckianav, but the bracts are narrower. Red veins and red streaks on the fruits afford a striking differentiating mark, though they are not absolutely lacking in the parent-species. A red hue may be seen on the calyx, and even the yellow color of the petals is somewhat deepened in the same way. Young plants are often marked by the pale red tinge of the mid-veins, but in adult rosettes, or from lack of sunshine, this hue is often very faint.

[535] The leaves are narrow, and a curious feature of this species is the great brittleness of the leaves and stems, especially in annual individuals, especially in those that make their stem and flowers in the first year. High turgidity and weak development of the mechanical and supporting tissues are the anatomical cause of this deficiency, the bast-fibers showing thinner walls than those of the parent-type under the microscope. Young stems of _rubrinervis_ may be broken off by a sharp stroke, and show a smooth rupture across all the tissues, while those of _lamarckiana_ are very tough and strong.

Both the giant and the red-veined species are easily recognized in the rosette-stage. Even the very young seedlings of the latter are clearly differentiated from the _lamarckiana_, but often a dozen leaves are required, before the difference may be seen. Under such circumstances the young plants must reach an age of about two months before it is possible to discern their characters, or at least before these characters have become reliable enough to enable us to judge of each individual without doubt. But the divergencies rapidly become greater. The leaves of _O. gigas_ are broader, of a deeper green, the blade more sharply set off against the stalk, all the rosettes [536] becoming stout and crowded with leaves. Those of _O. rubrinervis_ on the contrary are thin, of a paler green and with a silvery white surface; the blades are elliptic, often being only 2 cm. or less in width. They are acute at the apex and gradually narrowed into the petiole.

It is quite evident that such pale narrow leaves must produce smaller quantities of organic food than the darker green and broad organs of the _gigas_. Perhaps this fact is accountable partly, at least, for the more robust growth of the giant in the second year. Perhaps also some relation exists between this difference in chemical activity and the tendency to become annual or biennial. The _gigas_, as a rule, produces far more, and the _rubrinervis_ far less biennial plants than the _lamarckiana_. Annual culture for the one is as unreliable as biennial culture for the other. _Rubrinervis_ may be annual in apparently all specimens, in sunny seasons, but _gigas_ will ordinarily remain in the state of rosettes during the entire first summer. It would be very interesting to obtain a fuller insight into the relation of the length of life to other qualities, but as yet the facts can only be detailed as they stand.

Both of these stout species have been found [537] quite constant from the very first moment of their appearance. I have cultivated them from seed in large numbers, and they have never reverted to the _lamarckiana_. From this they have inherited the mutability or the capacity of producing at their turn new mutants. But they seem to have done so incompletely, changing in the direction of more absolute constancy. This was especially observed in the case of _rubrinervis_, which is not of such rare occurrence as _O. gigas_, and which it has been possible to study in large numbers of individuals. So for instance, the "red-veins" have never produced any dwarfs, notwithstanding they are produced very often by the parent-type. And in crossing experiments also the red-veins gave proof of the absence of a mutative capacity for their production.

Leaving the robust novelties, we may now take up a couple of forms, which are equally constants and differentiated from the parent species in exactly the same manner, though by other characters, but which are so obviously weak as to have no manifest chance of self maintenance in the wild state. These are the whitish and the oblong-leaved evening-primroses or the _Oenothera albida_ and _oblonga_.

_Oenothera albida_ is a very weak species, with whitish, narrow leaves, which are evidently incapable [538] of producing sufficient quantities of organic food. The young seedling-plants are soon seen to lag behind, and if no care is taken of them they are overgrown by their neighbors. It is necessary to take them out, to transplant them into pots with richly manured soil, and to give them all the care that should be given to weak and sickly plants. If this is done fully grown rosettes may be produced, which are strong enough to keep through the winter. In this case the individual leaves become stronger and broader, with oblong blades and long stalks, but retain their characteristic whitish color.

In the second year the stems become relatively stout. Not that they become equal to those of _lamarckiana_, but they become taller than might have been expected from the weakness of the plants in the previous stages. The flowers and racemes are nearly as large as those of the parent-form, the fruits only a little thinner and containing a smaller quantity of seed. From these seeds I have grown a second and a third generation, and observed that the plants remain true to their type.

_O. oblonga_ may be grown either as an annual, or as a biennial. In the first case it is very slender and weak, bearing only small fruits and few seeds. In the alternative case however, it [539] becomes densely branched, bearing flowers on quite a number of racemes and yielding a full harvest of seeds. But it always remains a small plant, reaching about half the height of that of _lamarckiana_.

When very young it has broader leaves, but in the adult rosettes the leaves become very narrow, but fleshy and of a bright green color. They are so crowded as to leave no space between them unoccupied. The flowering spikes of the second year bear long leaf-like bracts under the first few flowers, but those arising later are much shorter. Numerous little capsules cover the axis of the spike after the fading away of the petals, constituting a very striking differentiating mark. This species also was found to be quite constant, if grown from pure seed.

We have now given the descriptions of seven new forms, which diverge in different ways from the parent-type. All were absolutely constant from seed. Hundreds or thousands of seedlings may have arisen, but they always come true and never revert to the original _O. lamarckiana_ type. From this they have inherited the condition of mutability, either completely or partly, and according to this they may be able to produce new forms themselves. But this occurs only rarely, and combinations of more than one [540] type in one single plant seem to be limited to the admixture of the dwarf stature with the characters of the other new species.

These seven novelties do not comprise the whole range of the new productions of my _O. lamarckiana_. But they are the most interesting ones. Others, as the _O. semilata_ and the _O. leptocarpa_ are quite as constant and quite as distinct, but have no special claims for a closer description. Others again were sterile, or too weak to reach the adult stage and to yield seeds, and no reliable description or appreciation can be given on the ground of the appearance of a single individual.

Contrasted with these groups of constant forms are three inconstant types which we now take up. They belong to two different groups, according to the cause of their inconstancy. In one species which I call _O. lata_, the question of stability or instability must remain wholly unsolved, as only pistillate flowers are produced, and no seed can be fertilized save by the use of the pollen of another form, and therefore by hybridization. The other head comprises two fertile forms, _O. scintillans_ and _O. elliptica_, which may easily be fertilized with their own pollen, but which gave a progeny only partly similar to the parents.

The _Oenothera lata_ is a very distinct form [541] which was found more than once in the field, and recently (1902) in a luxuriant flowering specimen. It has likewise been raised from seeds collected in different years at the original station. It is also wholly pistillate. Apparently the anthers are robust, but they are dry, wrinkled and nearly devoid of contents. The inner wall of cells around the groups of pollen grow out instead of being resorbed, partly filling the cavity which is left free by the miscarriage of the pollen-grains. This miscarriage does not affect all the grains in the same degree, and under the microscope a few of them with an apparently normal structure may be seen. But the contents are not normally developed, and I have tried in vain to obtain fertilization with a large number of flowers. Only by cross-fertilization does _O. lata_ produce seeds, and then as freely as the other species when self-fertilized. Of course its chance of ever founding a wild type is precluded by this defect.

_O. lata_ is a low plant, with a limp stem, bent tips and branches, all very brittle, but with dense foliage and luxuriant growth. It has bright yellow flowers and thick flower-buds. But for an unknown reason the petals are apt to unfold only partially and to remain wrinkled throughout the flowering time. The stigmas are slightly divergent from the normal type, [542] also being partly united with one another, and laterally with the summit of the style, but without detriment to their function.

Young seedlings of _lata_ may be recognized by the very first leaves. They have a nearly orbicular shape and are very sharply set off against their stalk. The surface is very uneven, with convexities and concavities on both sides. This difference is lessened in the later leaves, but remains visible throughout the whole life of the plant, even during the flowering season. Broad, sinuate leaves with rounded tips are a sure mark of _O. lata_. On the summits of the stems and branches they are crowded so as to form rosettes.

Concerning inheritance of these characteristics nothing can be directly asserted because of the lack of pollen. The new type can only be perpetuated by crosses, either with the parent form or some other mutant. I have fertilized it, as a rule, with _lamarckiana_ pollen, but have often also used that from _nanella_ and others. In doing so, the _lata_ repeats its character in part of its offspring. This part seems to be independent of the nature of the pollen used, but is very variable according to external circumstances. On the average one-fourth of the offspring become _lata_, the others assuming the type of the pollen-parent, if this was a _lamarckiana_ or [543] partly this type and partly that of any other of the new species derived from _lamarckiana_, that might have been used as the pollen-parent. This average seems to be a general rule, recurring in all experiments, and remaining unchanged through a long series of successive generations. The fluctuations around this mean go up to nearly 50% and down nearly to 1%, but, as in other cases, such extreme deviations from the average are met with only exceptionally.

The second category includes the inconstant but perfectly fertile species. I have already given the names of the only two forms, which deserve to be mentioned here.

One of them is called _scintillans_ or the shiny evening-primrose, because its leaves are of a deep green color with smooth surfaces, glistening in the sunshine. On the young rosettes these leaves are somewhat broader, and afterwards somewhat narrower than those of _O. lamarckiana_ at the corresponding ages. The plants themselves always remain small, never reaching the stature of the ancestral type. They are likewise much less branched. They can easily be cultivated in annual generations, but then do not become as fully developed and as fertile, as when flowering in the second year. The flowers have the same structure as those of the _lamarckiana_, but are of a smaller size.

[544] Fertilizing the flowers artificially with their own pollen, excluding the visiting insects by means of paper bags, and saving and sowing the seed of each individual separately, furnishes all the requisites for the estimation of the degree of stability of this species. In the first few weeks the seed-pans do not show any unequality, and often the young plants must be replanted at wider intervals, before anything can be made out with certainty. But as soon as the rosettes begin to fill it becomes manifest that some of them are more backward than others in size. Soon the smaller ones show their deeper green and broader leaves, and thereby display the attributes of the _scintillans_. The other grow faster and stronger and exhibit all the characteristics of ordinary _lamarckiana_s.

The numerical proportion of these two groups has been found different on different occasions. Some plants give about one-third _scintillans_ and two-thirds _lamarckiana_, while the progeny of individuals of another strain show exactly the reverse proportion.

Two points deserve to be noticed. First the progeny of the _scintillans_ appears to be mutable in a large degree, exceeding even the _lamarckiana_. The same forms that are produced most often by the parent-family are also most ordinarily [545] met with among the offspring of the shiny evening-primrose. They are _oblonga_, _lata_ and _nanella_. _Oblonga_ was observed at times to constitute as much as 1% or more of the sowings of _scintillans_, while _lata_ and _nanella_ were commonly seen only in a few scattering individuals, although seldom lacking in experiments of a sufficient size.