It is for the same reason that we shall here use the plant for introducing Goethe's method. The following exposition, however, does not aim at rendering in detail Goethe's own botanical researches, expounded by him in two extensive essays, Morphology and The Metamorphosis of Plants, as well as in a series of smaller writings. There are several excellent translations of the chief paper, the Metamorphosis, from which the English-speaking reader can derive sufficient insight into Goethe's way of expressing his ideas; a pleasure as well as a profit which he should not deny himself.
Our own way of procedure will have to be such that Goethe's method, and its fruitfulness for the general advance of science, come as clearly as possible into view.3 Botanical details will be referred to only as far as seems necessary for this purpose.
The data for observation, from which in Goethe's own fashion we shall start, have been selected as best for our purpose, quite independently of the data used by Goethe himself. Our choice was determined by the material available when these pages were being written. The reader is free to supplement our studies by his own observation of other plants.
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Plates II and III show two series of leaves which are so arranged as to represent definite stages in the growth-process of the plant concerned. In each sequence shown the leaves have been taken from a single plant, in which each leaf-form was repeated, perhaps several times, before it passed over into the next stage. The leaves on Plate II come from a Sidalcea (of the mallow family), those on Plate III from a Delphinium. We will describe the forms in sequence, so that we may grasp as clearly as possible the transition from one to another as presented to the eye.
Starting with the right-hand leaf at the bottom of Plate II, we let our eye and mind be impressed by its characteristic form, seeking to take hold of the pattern after which it is shaped. Its edge bears numerous incisions of varying depths which, however, do not disturb the roundness of the leaf as a whole. If we re-create in our imagination the 'becoming' of such a leaf, that is, its gradual growth in all directions, we receive an impression of these incisions as 'negative' forms, because, at the points where they occur, the multiplication of the cells resulting from the general growth has been retarded. We observe that this holding back follows a certain order.
We now proceed to the next leaf on the same plate and observe that, whilst the initial plan is faithfully maintained, the ratio between the positive and negative forms has changed. A number of incisions, hardly yet indicated in the first leaf, have become quite conspicuous. The leaf begins to look as if it were breaking up into a number of subdivisions.
In the next leaf we find this process still further advanced. The large incisions have almost reached the centre, while a number of smaller ones at the periphery have also grown deeper into the leaf. The basic plan of the total leaf is still maintained, but the negative forms have so far got the upper hand that the original roundness is no longer obvious.
The last leaf shows the process in its extreme degree. As we glance back and along the whole series of development, we recognize that the form of the last leaf is already indicated in that of the first. It appears as if the form has gradually come to the fore through certain forces which have increasingly prevented the leaf from filling in the whole of its ground-plan with matter. In the last leaf the common plan is still visible in the distribution of the veins, but the fleshy part of the leaf has become restricted to narrow strips along these veins.
The metamorphosis of the delphinium leaf (Plate III) is of a different character. Here the plant begins with a highly elaborate form of the leaf, while in the end nothing remains but the barest indication of it. The impression received from this series of leaves is that of a gradual withdrawal of the magnificent form, revealed in its fullness only in the first leaf.