CH. XXXVI.

ORGANIC CHEMISTRY.

379

created in a living body are extremely complicated, making the whole subject very difficult to understand. Moreover, we do not pretend to follow out the particulars of any science; if you can remember the names of some of the great pioneers of chemistry from the time of Geber in the ninth century up to the days of Davy, Faraday, and Liebig, and have some slight understanding of the nature of the work they did, it is all we can attempt in a book of this kind.

Chief Works consulted.— Davy's 'Works,' 1840; Whewell's 'Inductive Sciences;' Dalton's 'Chemical Philosophy,' 1808; Dr. Henry's 'Memoir of Dalton,' 1854; Fownes's Chemistry;' Brande's 'Chemistry;' Faraday's Various Forces of Nature;' 'Edinburgh Review,' vol. xciv. Faraday.'

'Modern Chemistry;' Hoffmann, 'On Liebig and

CHAPTER XXXVII.

SCIENCE OF THE NINETEENTH CENTURY (CONTINUED).

The Organic Sciences are too difficult to follow cut in detail-Jussieu's Natural System of Plants-Goethe proves the Metamorphosis of Plants-Humboldt studies the Lines of average Temperature on the Globe-Extends our knowledge of Physical Geography-Writes the 'Cosmos'--Death of Humboldt in 1858.

THE short sketch of advances in modern chemistry given in the last chapter brings us to the end of the physical sciences, or those which deal more particularly with the properties of bodies, and the laws of their action upon each other. We must now pass on to those sciences which treat of the past and present history of the globe and the living beings which inhabit it. I shall not attempt to speak of these sciences separately, for it is clearly impossible without a great deal of special knowledge to follow the modern discoveries in physiology, anatomy, medicine, zoology, botany, and geology.

All these sciences had advanced rapidly since the time of Haller and Hunter, Linnæus and Buffon. Famous anatomists and physiologists such as the two Monros, father and son, in England, Bichat (1771-1802) in France, Camper (1722-1789) and Blumenbach (1752–1840) in Germany, had been carrying on the study of the comparative structure of men and animals, and training up students to understand, far more completely than before, the functions.

CII. XXXVII.

GOETHE A BOTANIST.

381

of living beings. And the followers of Linnæus all over the world had been collecting and sending home for comparison rare plants and animals formerly unknown, which were eagerly studied for the new light they threw upon those which had been already dissected and described.

And so it came to pass that towards the end of the eighteenth century men became eager not merely to examine separate specimens or structures, but to form theories about the living beings on the globe. They began to inquire why animals should all be so much alike in their general plan, and yet so different in their special characters; why the same part of the body should be made to serve for different purposes in different animals, instead of a special organ being provided; as, for example, the wing of the bat, which answers exactly to the front leg of a mouse, but is altered so as to be used for flying instead of walking. Then again, as the distribution of animals became better known, the question arose why certain kinds, such as kangaroos, should be found only in Australia, while they are wanting in all other parts of the world. Such general questions as these began to occupy the minds of naturalists, and we cannot close a history of science without trying to understand something of the attempts made to answer them, although they are so difficult that it will require all your attention and thought to understand them.

The Poet Goethe proves the Metamorphosis or Transformation of Plants, 1790.-One of the first men who threw any light upon the history of the growth of plants was the poet Goethe. Goethe had a deep love of Nature, as may be seen in many of his beautiful minor poems, and this love led him in the year 1780 to devote himself to the study of the anatomy of plants and animals.

Since the time of Linnæus botany had become very popular, and the two celebrated French botanists, Antoine de Jussieu and his son Bernard de Jussieu, had established. the Natural System of plants, which obliges men to observe every part of a plant before placing it in a class or order. You will remember that Linnæus suggested this method (see p. 211), but thought it too difficult for ordinary students, and even to this day the Artificial System of Linnæus is used side by side with Jussieu's.

The study of the Natural System, however, led botanists to observe more carefully the nature of plants and the manner in which they grow; and when Goethe turned his attention to botany he was very much struck with the power which plants have of transforming or changing the growth of their parts. For example, the common wild rose in the hedges has a crown of pink petals, with stamens and pistils in the centre; but the garden rose, which is nothing more than the wild rose grown in a better soil, has lost the stamens and pistils, or rather has changed them into flower-leaves, so that the whole flower is one mass of petals, and rarely forms any seeds.

It is clear, therefore, said Goethe, that the stamens and pistil of a plant are nothing more nor less than flower-leaves transformed into a peculiar shape, so that they serve to form seeds, and to carry on the life of the plant. And this is true of all the different parts of the plants. Wherever you look in the vegetable kingdom, you will find that every part of a plant is nothing more than stem or leaves altered in various ways to suit the work they have to do. Thus the stem of a geranium, the trunk of a tree, the twining stalk of the vine, the straw of wheat, the thorns of a rose-bush,

CH. XXXVII. THE METAMORPHOSIS OF PLANTS. 383

the runners of a strawberry, the roots of plants, and the fleshy potato, are all only different forms of stems and branches. Again, the two cotyledons of a seed which are well seen in the halves of a bean are but the first pair of leaves. Out of them grows the stem, and out of this, leaves of different forms according to the peculiar species of plant.

Then, as the plant developes, come the buds of the flower, but these again are only stems and leaves growing more thickly together. We find in different plants every variety of flower from mere green leaf-like blossoms to the most gorgeous colours. The green leaves called sepals, which lie under the yellow petals in the buttercup, are transformed into brilliantly coloured petals in the tulip, while in some cases, such as occasionally in white clover, the whole flower, sepals, petals, pistil and stamens, has been known to be changed into little leaflets growing as if upon a branch.

For this reason gardeners find it possible to cultivate a plant so that it shall be all leaves and no flower, or, on the other hand, shall have a gorgeous flower while the leaves remain small and insignificant; or, as in the potato or the turnip, they can increase the size of the root at the expense of the leaves and flowers. And thus we are led to see that all the different parts of a plant are only peculiar transformations of simple stems and leaves, such as we find in mosses and the lowest forms of plants.

This beautiful truth of the transformation or metamorphosis of plants we owe to the poet Goethe; for though Linnæus suggested it rather vaguely in some of his writings, and a botanist named Wolff seems also to have taught it, yet it was Goethe's essay on the 'Metamorphosis of Plants,'