METAMOKPHOSIS OF OEGANS OF PLANTS. 
9T 
being tlie relation between the calyx and corolla, if sepals, or 
the parts of the calyx, are transformed leaves, so must be the 
petals. 
110. The stamens which occupy one or more whorls next 
within the corolla exhibit no resemblance to leaves, yet we have 
seen that they do not differ from them in nature. We will add, 
that in the Nymphsea odorata^ or white water-lily, the transi- 
tion of sepals into petals, and of petals into stamens, may be 
distinctly traced. The four or five sepals are green on the out- 
side, but somewhat petal-like within ; the outermost of the 
whorls of petals are tinged with green. Between the perfect pe- 
tals and the stamens there is a row of organs which are neither 
v>ne nor the other, but diminutive petals, with anthers upon 
their summits. The more j)erfect formation of stamens next 
aj^pears. In some cases we see the retrograde process of sta- 
ofiens being changed to green leaves. The simple pistil is 
tbrmed of 2i folded leaf and a compound pistil of a whorl of 
)eaves, pressed and cohering together. In the Iris we see 
three dilated stigmas which are identical in form and appear- 
ance with so many petals. 
111. By expansion and contraction the great objects of nature 
seem to be efiected in the vegetable growth. From the seed to 
the fullest development of the cauline leaves there is expansion^ 
to form the hracts and calgx there is contraction. The corolla is 
produced by a new expansion j the stamens and pistils by an- 
other contraction. These expansions are often very great in the 
fruit ; and lastly, the greatest degree of concentration or con- 
traction is in the seed. Fruits are transformed leaves ; — the 
follicle is a simple leaf folded upon itself, with its two margins 
soldered together ; the silique is formed of tvjo leaves folded 
and combined together ; the more compound seed-vessels are 
produced from a verticil of several folded lecoves^ collected round 
a common center, and soldered together by their contiguous 
margins. Each of the folded leaves is called a carpel. The 
analogy of the carpels with the organs wdiich precede them, is 
sliown by the fact that the stigma often remains upon the 
ovary. The inflated portion of the carpel forms a case for 
the young seeds. It has been supposed that seeds are pro- 
duced on the veinlets of the leaf projecting beyond the mar- 
gin. The ovules, or rudiments of seeds, have been found, 
by a retrograde or abnormal process, to exhibit their tender 
cotyledons in the form of leafy expansions. "Each simpl<i 
fistil is formed of a folded, metamorphosed leaf, and is term- 
ed a carpel., or little fruit. The ovules are usually produced on 
the margins of the metamorphosed leaf, and are arranged along 
IJO. Relation between sepals and petals— The pistil a folded leaf.— Ill Expansion and contMto 
lion — Exanij)les — Fruits— Carpel— Origin of seeds. 
5 
