METAMORPHOSIS OF ORGANS OF PLANTS. 97 



being tlie relation between the calyx and corolla, if sepals, or 

 the i)arts of the calyx, are transformed leaves, so must be the 

 petals. 



110. The stamens which occnpy 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 wdll add, 

 that in the Nymphsea odorata^ or white water-lily, the transi- 

 tion of sej)als into petals, and of petals into stamens, may be 

 distinctly traced. The four or five sej^als 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 

 one nor the other, but diminutive petals, with anthers upon 

 their summits. The more perfect formation of stamens next 

 appears. In some cases we see the retrograde process of sta- 

 mens being changed to green leaves. The simple instil is 

 formed of 2^. folded leaf and a compound pistil of a whorl of 

 leaves, pressed and cohering together. In the Iris we see 

 three dilated stigmas which are identical in form and appear- 

 ance with so many jDetals. 



111. By expansion and contraction the great objects of nature 

 &eem 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 / 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 siliqne is formed of tv:o leaves folded 

 and combined together ; tlie more compound seed-vessels are 

 produced from a verticil of several folded leaves^ 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 car^^els with the organs which precede them, is 

 shown 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 simple 

 pistil 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 



110. Relation between sepals and jietals— The pistil a folded leaf. — 111. Expansion and contrau 

 tion— Examples— FruiiR—Caippl — Origin of sneds. 



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