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goethe's essay on the metamorphosis op plants. 
II. Development of the Cauline Leaves from Node to Node. 
19, We may now closely watch the successive development of the leaves, as the gradually 
progressing actions of nature are now open before our eyes. Some few of the leaves have 
been present already in the seed-eorn, folded up between the cotyledons, and in this state 
are called the plumule (gemmule, or primordial leaves). Their shape, if compared with the 
cotyledons and succeeding leaves, is different in different plants ; but still, in general, they 
differ from the cotyledons in being flat, tender, and, in short, more like true leaves, of a green 
colour, with a bud at their base ; so that their affinity with the other leaves is no more to 
be doubted : generally they are inferior to true leaves, by not having their margin so 
completely developed. 
20. Meanwhile the ulterior development goes on from node to node throughout the whole 
leaf, elongating the central rib and spreading out side ribs, more or less inclining towards 
the sides. The different relations of the ribs towards each other are the principal cause 
of those many varieties of shape in leaves. Now the leaves may appear crenate, deeply 
incised, or composed of several smaller leaves, in which case they seem to form a perfect 
little twig. The Date Palm furnishes us with a striking example of the progressive 
modification from the most simple form to the most complicated. After several succeeding 
leaves, integral and simple, the middle rib begins to push on and elongate, the fan-shaped 
simple leaf is torn, separated into many leaflets, and another highly complicated twig-like 
leaf is developed. 
SI. In the same degree, that the leaf becomes more developed, the leaf-stalk de- 
velopes itself, either as an immediate part of the leaf, or as a distinct organ, which 
afterwards may be easily separated from the leaf. 
22. That this proper leaf-stalk (petiole) has a great inclination to assume the shape of 
the leaf, we may see in different plants, as in the Orange for example ; and its organisation 
will give occasion to some observations, which we shall pass by for the present. 
23. At the same time we shall not yet take any notice of the stipules ; we only remark 
here, that if they form part of the petiole, they will likewise in the most remarkable 
manner be transformed with the metamorphosis of the leaf-stalk. 
94. As the leaves derive their principal food from the sap of the stem, more or less 
watery and undigested, so they derive their greater development and refinement from light 
and air. When we see the cotyledons produced in the seed corn not at all or very 
incompletely organised and developed, and as if filled with raw and undigested sap, so we 
shall see the leaves of aquatic plants, which grow under the surface of water, not so 
perfectly organised as those exposed to the free air. Plants will even produce smoother 
and less organised leaves in confined, low, and moist situations, which, if removed to more 
exposed places, will become rough, hairy, and altogether of a finer organisation. 
25. In the same manner, we find the anastomose of the vessels which produce the 
cellular tissue of a leaf, by springing from the ribs and trying to meet at their extremities, 
if not solely produced by the influence of rarefied gases, still greatly assisted by them. 
If leaves of plants growing under water assume the shape of filaments, or become ramified 
like antlers, we feel inclined to ascribe this formation to the absence of a perfect anasto- 
mose. The growth of the Ranunculus aquatilis illustrates this theory in an evident 
manner ; those leaves which are produced under water consist of thread-like ribs only, but 
those produced above water have their ribs filled with the cellular tissue, combining them 
into one integral leaf, by the perfect action of the anastomose. We find even leaves where 
this action has been in operation only partly, that in consequence they are partly integral 
and partly filiform, thus clearly showing the transition. 
26. Experience has taught us that leaves consume different gases, which enter into 
combination with their internal fluids, and there remains no doubt that this digested sap 
returns to the stem, and forms the chief food of the bud, in or near the axil of the leaf. 
Scientific men have analysed these gases, contained in leaves and stems, and have perfectly 
ascertained this fact. 
27. We observe in some plants that one node comes out of another. With the 
