and sepals. In the " Hundred-leaved Rose" you will find illustrated, in an equally plain and perfect manner, the likeness of sepals to the green leaves of the rose plants; and in the geranium the same phenomenon is occasionally seen. From the green calyx with its sepals to the coloured corolla with its petals the transition is just as readily made. In Camellia Japonica we behold such an interesting and gradual transition from sepals to petals. In some plants (e.g. Indian Cress and Fuchsia) the calyx, instead of being green, may be coloured; this fact indicating a transition from calyx to corolla in one way. On the other side, we find the petals may be developed as ordinary leaves, and thus we learn that petals, like sepals, are simply modified leaves.

A

The case for the full substantiation of Goethe's maxim grows stronger when we approach stamens (Fig. 1, st) and pistil. If the stamen be in reality a leaf, it is also certain that it resembles a leaf much less closely than the sepal or the petal. The stamen is a stalked organ, as we have seen, and bears in its head or anther the yellow pollen. This head seems to

HOON!

B

0011

Fig. 2. STAMENS CHANGING TO PETALS.

represent the folded blade of the staminal leaf, but have we any proof that our conjecture is probable or correct? Let

the facts of botany reply. Here is a Petunia, for instance, in which the stamens are replaced by stalked leaves; there a white Water Lily (Fig. 2, B) and a Double-rose (Fig. 2, A), in both of which cases you may observe the transition stage whereby the stamen (4, 6) becomes a petal; whilst the petal in the rose may become in its turn a sepal (Fig. 2, A, 1). So, too, in the common tulip, the three parts of the pistil and the six stamens may all be transformed into petals. Nor does the central organ of all, the seed-producing pistil, escape these metamorphic changes. The double-flowering Cherry (Fig. 3) FLOWERING CHERRY. Shows its carpel in the shape of a green leaf (b). The willow flowers show us gradations from the leaflike carpel to the altered stamen, and thence to the ordinary leaf;

a

Fig. 3. DOUBLE

and you may, lastly, find in some plants, as in the monstrous specimens of Dutch Clover, that every part of the flower becomes a leaf. Goethe's own words regarding the pistil succinctly express the true state of matters regarding its abnormal history: "If we keep in view the observations which have now been made, we shall not fail to recognise the leaf in all seed-vessels, notwithstanding their manifold forms, their variable structure, and different combinations." Thus Goethe's generalisation finds its best proof in the facts of vegetable monstrosities. And the science of likenesses, tracing nature in her bypaths of development, discovers that, whatever may be said of the first beginnings of plant life on the globe, the later development which has given us the flowering plants has apparently been directed wholly, or in greater part, towards the elaboration of the leaf. To the evolution of the leaf, as the science of likeness proves, we owe the wondrous beauty of the flowers, which, like the stars of the poet, brighten earth's otherwise dull firmament.

The flower, however, is not the only part of the plant which has received abundant elucidation at the hands of the science of likenesses. The ingenuity of Nature and the prolific nature of the expedients by which she developed structures to serve her varied ends, formed of old two of the stereotyped sources of wonder by the recital of which philosophers were wont to regale their auditors. This fertility of device in using simple means to effect important ends receives a new reading from the study of homology. We now perceive that the modifications effected by nature represent the utilisation of like parts in divers ways. Just as essentially similar limbs may be employed in the animal world for very different purposes, so the variations of similar parts in plants may illustrate what is meant by "homoplastic" organs—that is, the adaptation to new and varied ways of life, of the common belongings of the plant world. Our comprehension of this truth may be firstly assisted by an example culled from the animal world. The idea that Nature, "in framing her strange fellows," and in developing the unusual and unwonted, should effect her purpose by the creation of new structures and fresh parts, is an idea for which there apparently exists the warrant of common sense. But let us see if the way of Nature in such a case is not rather by the elaboration and modification of already existing parts. Take as an illustrative case the Tortoise (Fig. 4) and its structure. No single animal form stands apparently more aloof from its neighbours of the reptile class than the sluggish chelonian. Enclosed in a bony box, its structure seems to be unique, and its relations

to the serpent, lizard, or crocodile extremely unapparent. But what

has comparative anatomy to

say respecting the building of the chelonian house? Look at the roof formed by the greatly expanded ribs and solid spine. Look at its sides formed by the cartilages or ends of the ribs; and its floor formed by certain skin-bones comparable roughly in their nature to

the large scales of the crocodile's under surface, and in any case presenting us with no structures unusual or foreign to the reptile class. The boxlike body of the animal is, in short, formed by so much of its skeleton, and so many of its scales, altered and modified to suit the animal's way of life; and presents us thus with no new thing in the way of structure, but with an elaboration of the common elements of the reptile body.

More interesting, perhaps, because more complex in their relations, are the changes which occur in the lower jaw and ear as we ascend from the fishes as the lowest vertebrates to Man and quadrupeds as the highest. We could not find a better example of the manner in which Nature moulds the same elements into widely different forms than such a subject. Homology teaches us clearly enough that in the elaboration of the skull, as in the modification of the tortoise-skeleton as a whole, new parts and new organs are evolved simply and for the most part by the alteration and higher development of the original type. When we examine the lower jaw and its connections with the skull in any vertebrate animal below the rank of the quadruped, we find that the jaw is attached to the skull by the intervention of a special bone called the "quadrate bone." The manner in which lower jaw and skull are connected in Man and quadrupeds is very different from the latter arrangement. In Man, as every one knows, the lower jaw works upon the skull directly and of itself, and the "quadrate bone," which one sees so distinctly in the reptile, bird, frog, or fish, is apparently wanting in higher vertebrate life. Is the skull of the quadruped, then, modelled, as regards its lower jaw and articulations thereof, on a different type from that seen in the lower vertebrate? Comparative anatomy supplies the answer in very different fashion. Attend for a moment to the disposition of the parts of the internal ear, which in quadrupeds we find to exist within the skull and just above the lower jaw. We

find three small bones (Fig. 5, A, m, i, c,) to connect the "drum" of the ear with the internal hearing apparatus. Of these three bones, one shaped somewhat like a hammer is named the malleus (m), and

to this bone our attention must be specially directed. For when we trace this bone downwards through the reptiles and birds towards the fishes, we discover that it alters its relations to the ear and assumes new ones with the lower jaw. In reptiles and birds, for example, we find the malleus to be of large size, and to be divided so that one part (B, m) becomes transformed into the "quadrate bone," and another (B, m1) into the upper part of the lower jaw () itself. In the fish a third bone (c, m") may actually appear in connection with the lower jaw (j), and as the result of the division of the part representing the "malleus" of Man and quadrupeds. So that, divesting the subject of all technicality, we may say that, as we first enter the vertebrate sub-kingdom, we find the "malleus" to be represented in the fishes by no less than three bones (c, m, m', m'') which are connected with the upper part of the lower jaw and lie outside the ear altogether. Next, in the reptile and bird we find a modification of this arrangement to hold good. Here the malleus is divided into two portions (m, m1) only; these parts, however, being still concerned in the articulation of the lower jaw (j). But in Man and his neighbourquadrupeds, these outside bones become pushed upwards in the course of development, and are finally enclosed within the skull, thus appearing as the "malleus" of the ear (a, m), having no connection with the jaw, and being concerned in the higher function of conveying impressions of sound to the internal ear. The upper part of the lower jaw of the lower vertebrate is in fact taken into the interior of the skull and ear, when we reach the quadruped class. The two companion bones (c, i) of the malleus in the ear, likewise represent separate parts of the skull, which in higher life become modified for the hearing function. And a glance at the accompanying diagram will serve to show how the other bones—“ incus" (¿) and “stapes” (c)—of the quadruped ear are represented wholly or in part in lower life, and how they attain their higher place and function simply as the result of modification, and the evolution of a new structure from the

materials of an already existing type. Such modification is simply part of the wider process we see everywhere illustrated in animal life at large, whereby complication and diversity of structure and form are the results of no new creations, but of the development, the splitting up, and differentiation of already existing parts.

So is it also with plants in some of their most unusual aspects. The strange features in animals and plants are in reality but the altered "commonplace of nature." By way of illustration, the subject of the threadlike "tendrils" of plants presents itself in a prominent manner. It would be hard to discover any organs of plants which are better known than these. Poetic allegory itself has ever found in the simile of the "tendrils" the best guise under which the affections of mankind might be shadowed forth; and that the weak-stemmed plants climb by the aid of these organs is not a matter requiring even a primer of botany for its verification. Now, plants of very varied nature possess these organs; and the question arises, are these tendrils new and special organs in such plants as possess them, or are they but modifications, like the home of the Tortoise, of familiar structures? Let the science of likenesses reply, by directing our attention to the general form of

Fig. 6. A LEAF
AND ITS PARTS.

the leaf. Every ordinary leaf (Fig. 6) con

sists, as we know, of a stalk or petiole (p) and a blade or lamina (1), and when we look at the apple leaf (Fig. 6), or at a rose leaf, we may see at the point where the leaf stalk leaves the stem two little wing-like appendages, called stipules (ss), and which are to be regarded as normal parts and appendages of the leaf. These stipules are large in the pansy p tribe, and are also prominent in the beans and peas, whilst in one of the vetches (Fig. 10) -Lathyrus aphaca, the Yellow Vetch-the stipules, as we shall see, may actually represent the leaves. In many other plants, on

the contrary, no stipules occur.

Now let us examine the leaf of the Common Pea (Fig. 7). It is a compound leaf, and we notice that the tendrils seem to grow out at the sides and at the end of the leaf stalk. The tendrils (tt) here are at once seen to exist in the place of some of the leaflets (ƒ), and,