Species and Varieties, Their Origin by Mutation

Among the same lot of plants individual differences almost always occur. They are partly due to inequalities already existing in the seeds, and partly to the diversity of the va...

Vegetative propagation has the great advantage of exempting the varieties from regression to mediocrity, which always follows multiplication by seeds. It affords the possibility...

In some few instances it is obvious that this variability is of later date than culture. The most conspicuous case is that of the coconut. This valuable palm is found on nearly...

Obviously, this elimination conduces only to a partial purification. The conspicuous plants will be destroyed, but a greater number of hybrids will remain, still concealed by th...

Natural selection occurs not only in the wild state, but is also active in cultivated fields. Here it regulates the struggle of the selected varieties and improved races with th...

Isolated plants of _Linaria vulgaris_ do not produce seed, even if freely pollinated by bees. Pollen from other plants is required. This requirement is not at all restricted to...

From these several observations and experiments it may be seen, that it is not at all easy to keep the common varieties of cereals pure and that even the best are subject to the...

It is worth while to dwell a moment on the capacity of the individuals with red flowers to reproduce the striped type among their offspring. For it is manifest that this latter...

In other cases the differing forms are observed to grow near each other, sometimes in neighboring provinces, sometimes in the same locality, growing and flowering in mixtures of...

We now consider the cases of the loss of superficial organs, of which the nectarines are example. These are smooth peaches, lacking the soft hairy down, that is a marked peculia...

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 nu...

Besides these rare cases there are quite a number of cruciferous species on record, which have been observed to bear bracts. Penzig in his valuable work on teratology gives a li...

In a paper published in 1862 Sir William Thomson (now Lord Kelvin) first endeavored to show that great limitation had to be put upon the enormous demand for time made by Lyell,...

The best proof is afforded by the varieties which grow wild in localities where they are quite isolated from the species, and where for this reason, no possibility of crossing d...

In the same way double ascidia may be made use of to explain the foliar cups of the teasels and some other plants, as for instance, some European snakeroots (_Eryngium maritimum...

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...

On a visit to a nursery at Erfurt I once inspected an experiment with a new double variety of the common blue-bottle or blue corn-flower. The plants were dependent on the weathe...

Now it is evident that the colors and forms of the flowers can only be clearly distinguished, when they are fully displayed. Furthermore it is impossible to destroy every single...

Reversion may occur either by buds or by seeds. It is highly probable that it occurs more readily by sexual than by asexual propagation. But if we restrict the discussion to the...

Leaving these obvious cases of double adaptation, there still remains one point to be considered. It is the dwarf stature of so many desert and alpine plants. Are these dwarfs o...

The peloric toad-flax in my experiment was seen to arise thrice from the same strain. Three different individuals of my original race showed a tendency to produce peloric mutati...

Thus far we have an ordinary case of reversion. But the important side of the phenomenon was, that each plant exactly "recollected" from which parent it had sprung. All of those...

Luther Burbank of Santa Rosa, California, has produced a great many hybrid brambles, the qualities of which in many respects surpass those of the wild species. Most of them are...

Unfortunately the practical value of these calculations is not very great. They indicate the size of the cultures required to get all the possible combinations, and show that in...

Moreover there is as yet no reason for trying to make a complete analysis of all the characters of a plant. No doubt, if attained, such an analysis would give us a deep insight...

[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...

Besides this limited study, we may compare the numerous individuals of one locality or of a large plot of cultivated plants with one another. In doing so, we are struck with the...

From this discussion we may infer that the chances of discovering new mutating species are great enough to justify the utmost efforts to secure them. It is only necessary to obs...

Three cases are to be distinguished as to heredity. Many plants are so constituted as to be fertilized with their own pollen. In this case the visits of insects have simply to b...

The same phenomenon of a lateral doubling of leaflets may of course be met with in other instances. The common laburnum has a variety which often produces quaternate and quinate...

Of course the historical part is only a hasty survey of the question and will only give such evidence as may enable us to get an idea of the [490] chances of success for the exp...

Secondly the instability seems to be a constant quality, although the words themselves are at first sight, contradictory. I mean to convey the conception that the degree of inst...

On this point Darwin has recognized two possibilities. One means of change lies in the sudden and spontaneous production of new forms from the old stock. The other method is the...

I wish to point out that the decision of what is to be expected from deviating specimens may become manifest within one or two generations. Even the generation grown from the se...

Finally, and in order to come to a definite choice of research material, we should keep in mind that the chief object is to ascertain the relation of the offspring to their pare...

Of late the same mutation has occurred in the garden of C.A. White at Washington. The parent form in this case was the "Acme," of the ordinary weak and spreading habit of growth...

In conclusion something is to be said about the choice of the seed. Obviously it is possible to compare seeds of different origin by sowing and treating them in the same way, gi...

Uniting the heads of the vertical rows of figures by a line, the form corresponding to Quetelet's law is easily seen. In the main it is always the same as the line shown by the...

We now come to the field pansy, the _Viola arvensis_, a very common weed in the grain-fields of central Europe. I have already mentioned its small corolla, surpassed by the lobe...

[785] is exactly what is gained by repeated selections. To my mind this reduction of the size of the cultures is probably the sole effect of the repetition. But experience is la...

_Scintillans_ and _elliptica_ constitute exceptions to the rule given. They repeat their character, from pure seed, only in part of the offspring. I have tried to deliver the _s...

[120] Indeed it may be surmised that this has been its chief and prominent function. Taking up again our metaphor of the sieve we can assert that in such cases climate and soil...

Experience must decide between the two main theories. It demonstrates the existence of polymorphous genera, such as _Draba_ and _Viola_ and hundreds of others. They clearly indi...

Among all the previously described cases of horticultural plants and monstrosities there is no clearer case of an ever-sporting variety than this one of the water-persicaria. Th...

THE purpose of these lectures is to point out the means and methods by which the origin of species and varieties may become an object for experimental inquiry, in the interest o...

If it had been possible to apply this principle to twisted and fasciated plants, and perhaps even to other monstrosities, I think that it will readily be granted that the chance...

Haeckel, 707 Half-races, 358, 372, 409, 419, 424, 427, 428 Hall, 444 Hallet, F.F., 109 Harebell, 232 peach-leaved, 234 Harris, Arthur, 825 Harshberger, John W., 591 on _Euphorbi...