Modifications in Plants

All botanists know that the plants which they take from the place where they were born to the gardens where they are cultivated undergo there gradual changes which end up making them unrecognizable.

Many naturally very hairy plants in this way become smooth, or almost so; a number of those which were low and trailing straighten up their stem; others lose their thorns or protrusions; still others in our climate change from the woody and perennial stem conditions which they had in the hot climates where they used to be, to a herbaceous state, and among them several are nothing more than annuals.

Finally, in our gardens the dimensions of these plants’ parts themselves undergo very significant changes.

The effects of these changed circumstances are so well recognized that botanists do not like to describe their garden plants until they are no longer recent cultivations.

Is not cultivated wheat (triticum sativum) a plant brought by man to the condition in which we see it today? Can anyone tell me in what country a similar plant lives naturally, that is, without being the result of its cultivation in some place near by?

Where do we find in nature our cabbage, lettuce, and so on, in the state where we produce them in our vegetable gardens? Is the case not the same with respect to the number of animals which domestication has changed or considerably modified?

How many different races of chickens and domestic pigeons we have acquired by raising them in different circumstances and different countries! How futile it is now to seek to find such animals in nature!

Those which are the least changed (undoubtedly because their domestication is more recent and because they do not live in a climate foreign to them) in some of their parts display differences no less significant through the habits which we have made them acquire.

Thus our domestic ducks and geese find their type again in wild ducks and geese, but ours have lost the ability to rise up into the high regions of the sky and to fly across large territories. Finally a real change has occurred in their parts in comparison with the parts of the animals of the race from which they originated.

Who is not familiar with the fact that when some bird from our climate raised in a cage and living there five or six consecutive years is after that returned to nature, that is, given back its liberty, it is then no longer in a condition to fly like those similar to it which have always been at liberty?

The slight change of circumstances working on this individual has, in truth, only diminished its capacity for flying and, undoubtedly, has not brought about any alteration in the shape of its parts.

But if many successive generations of individuals of the same race were held in captivity over a long period of time, there is no doubt that even the shape of the parts of these individuals would have gradually undergone noticeable changes.

This would be all the more reasonable if, in place of keeping them in a simple captivity constantly maintained, this circumstance had been simultaneously accompanied by a change into a very different climate and if these individuals had grown accustomed, by degrees, to other forms of nourishment and to other actions for obtaining it. It is certain that these combined circumstances, once they become constant, would then create imperceptibly a new and totally special race.

Where do we see now in nature the many races of dogs which, as a result of the domesticity to which we have reduced these animals, we have brought into existence in the form they are today? Where do we find these mastiffs, greyhounds, water spaniels, spaniels, lap dogs, and so on and so on, races which display among themselves greater differences than those which we acknowledge as specific differences among animals of the same genus living freely in nature?

Undoubtedly, some first unique race, at the time very close to the wolf (if that is not in itself the true type), was domesticated by man at some epoch or other.

This race, which did not then manifest any differences among its individuals, was gradually dispersed with human beings into different countries and climates.

After some length of time, these same individuals experienced the influences of their surroundings and of their various habits which they had been made to acquire in each territory, underwent some remarkable changes, and formed different special races. Now, human beings, who, for trade or for some other sort of interest, move over very considerable distances, carried different races of dogs formed in countries far away into densely inhabited places, like great capital cities. At that time the crossbreeding of these races through reproduction thus gave rise successively to all those which we know about nowadays.

The following fact proves (with respect to plants) how much a change in some important circumstance has an influence on changing the parts of living organisms.

Whenever the plant ranunculus aquatis is immersed in water, its leaves are all markedly serrated and finely divided.

But when the stem of this plant reaches the surface of the water, the leaves which develop in the air are enlarged, round, and simply lobed.

If some feet of this plant succeed in pushing into a soil which is only humid, without being underwater, their stems then are short and none of their leaves is divided up into tiny sections.

This example gives rise to the plant ranunculus hedereaceus, which botanists, when they encounter it, consider a species.

There is no doubt that, so far as animals are concerned, important changes in the circumstances where they usually live produce similar changes in their parts.

But here the changes are much slower manifesting themselves than in the plants. Consequently, they are less perceptible to us and their cause less recognizable.

As for the circumstances which have the most power to change the organs in living bodies, the most influential is undoubtedly the diversity in the locations where the animals live. But, in addition, there are many others which later have a considerable influence in producing the effects we are discussing.

Different places have a different nature and quality, on account of their positions, compositions, and climates.

Each place itself changes, over time, in exposure, climate, nature, and quality.

• This happens so slowly that we attribute to that place a perfect stability.

In both cases, these altered locations change correspondingly the circumstances relevant to living things who live there.

These circumstances then produce other influences on these living things themselves.

From that, we perceive that if there are extremes in such changes, there are also slight modifications as intermediate degrees which fill up the gap between the extremes.

Consequently, there are also modulations in the differences within a species.

Thus the Earth shows a diversity of circumstances which is allied throughout to the diversity in the forms and the parts of animals.

• This is independent of the special diversity which results from the progress in the complexity of organic structure in each animal.

Everywhere where animals can live, the circumstances which create there an order of things remain the same for a long time and do not really change except with such an excessive slowness that man is not capable of perceiving it directly.

He is obliged to consult the monuments to recognize that in each of these places the order in things which he finds there has not always been the same and to sense that it will change once again.

The races of animals living in each of these places must thus preserve their habits for quite a long time; hence the apparent permanence to us of what we call species, a permanence which has given rise in us to the idea that these races are as old as nature.

But in the different habitable locations on the surface of the earth, the nature and situation of territories and climates there constitute for animals, as for plants, circumstances different to all sorts of degrees.

The animals inhabiting these different places must therefore be different from each other not only because of the state of complexity in the organic structure of each race but also because of the habits which the individuals of each race have been forced to acquire there.

The naturalist traversing parts of the earth’s surface sees conditions change proportionally to the change in the characteristics of its species.