long siliquas. These are full of petals, and if carefully examined appear to be whorled, with traces of stamens and pistil within them; so that they represent flower-buds, but of which petals form the greater part; similarly, Rhododendrons and other flowers are known to bear imperfect flower-buds within the ovary (Fig. 79, b). Anthers occupying the place of stigmas appear to have occurred in Campanula,* Snowdrop, and double Tulips. The substitution of stamens for the entire pistil is of a less usual occurrence than the staminody of its parts: for cases, the reader may consult Masters's Teratology. In a species of Orchis, probably O. Morio, the ovaries were wanting altogether, a long pedicel taking their place, and within the reduced and regular perianth were two anthers on opposite sides (Fig. 23, a, p. 92), an apparent compensation in lien of the pistil. The next and most frequent case of metamorphosis is that of conversion of carpels, and usually the stamens as well, into petals, or the so-called "doubling" of flowers. This is usually accompanied by a change from whorls to spirals with a multiplication of the parts. Thus, in a double Wallflower, I have counted more than fifty petals spirally arranged. With regard to the petalody of the pistil, as Dr. Masters observes, "this is much less common than phosed sub-petaloid carpel of Polyanthus. the corresponding change in the stamens. Fig. 80. — MetamorIt generally affects the style and stigma only, as happens normally in Petalostylis, Iris, etc." Fig. 80 illustrates a metamorphosed carpel of Polyanthus, with a broad coloured appendage to the style. In some double flowers the carpels only are petaloid. *Teratology, p. 300. † Ibid., p. 299. Ibid., p. 296. This has been observed in Anemone nemorosa, cultivated varieties of Ranunculus, Violet, and Gentiana Amarella. RETROGRESSIVE METAMORPHOSES OF STAMENS.-For the stamens to become petaloid, it is extremely common, as in double flowers, and such a change may represent what is normally the case in Water-lilies, Canna, and Atragene (Fig. 44, p. 141). Changes may apply to the anther lobes, connective, or filament, or to all together. Fuchsias often bear filaments with petaloid expansions of the apex, at the base of which are one or two anthers showing varying degrees of degeneration. This is a very similar condition to one in Petunia, described by Dr. Masters, in which the connective had developed into a green roundish blade bearing two anther cells at the base (Fig. 81).* In such cases, it seems to be the connective which has expanded outwards and become the blade of the petal or leaf. Similarly, in the Fig. 81.-Foliaceous connective of Petunia Fig. 82.-Petalody, or "hose-in-hose " form, (after Masters). of connectives in a double Columbine. double Columbine petalody of the connective sometimes takes place (Fig. 82).† Commelina alba has also furnished a case of an anther lobe becoming petaloid. CAUSES OF "DOUBLING."—There can be no doubt that petalody results from a weakened reproductive energy, especially that of the androecium, which can become constitutional and may be hereditary and transmissible by crossing. *Teratology, p. 254. + Ibid., p. 293. Cases seem clearly to show that a barren and dry soil, as well as a very dry atmosphere, are prominent causes for its appearance. Thus Mr. Darwin described a double Gentiana Amarella,* growing "on a very hard, dry, bare, chalky bank." T. S. speaks † of a double Potentilla as "growing along a high wall, on a dry raised bank close to a beaten path, adjoining a gravelly field." Again, a writer in Gartenzeitung alludes to the raising of double Stocks, and says that they should only have "just enough water for their preservation," and that "the starved state of the plants" causes doubling. He alludes to Camellias, also, as becoming double when grown in a dry soil. Kerria Japonica becomes double in Europe, in consequence of its missing the wet season of Japan. It is well known that double flowers are more easily raised on the continent than in England, probably from a like cause, as our atmosphere is considerably more charged with moisture than a continental one. In raising double Stocks, it is customary to procure seed from the flowers on axillary shoots which have a weaker reproductive energy than those growing on the primary or central axis, the seeds being smaller and often misshapen. The above causes are, therefore, suggestive; in that if a somewhat elevated, dry, and poor soil, one devoid of phosphates, etc., be provided, the probability is that petalody will ensue. Having once shown a trace of the malady, florists know how to proceed in order to propagate and transmit the affection. There remains one other floral metamorphosis, and that is of petals into sepals. This condition approximates to virescence of the corolla, so that in many cases such a change could scarcely be called sepalody. But M. Godron has shown that when Ranunculus auricomus appears to be † Ibid., 1866, p. 973. *Gard. Chron., 1843, p. 628. apetalous or to have a corolla consisting of a few petals only, it is due to the fact that the petals which are wanting are really present, but have become calycine. ORIGIN OF HOMOLOGY.-Though we cannot penetrate into the arcana of life, nor trace the workings of its forces which bring about the development of any organ whatever, I think we can at least reach the physiological starting-point, so to say, of all these changes which I have briefly described. I have already mentioned that we may consider a vascular cord as the fundamental "floral unit,” and as all cords are identical in character as long as they are within a pedicel, and, as far as one can observe, identical also in character even when they have penetrated the different organs, we at once see that there is a common source for each and all. Secondly, when we trace these cords from the receptacle or axis into the floral members, we soon discover that any cord can supply two, three, or more totally different organs with their respective branches, as in the case of Campanula medium described above (p. 43). Indeed, starting, say, with five cords in a pedicel, they can supply any number of organs ad libitum, however diverse in character and however numerous they may be. Hence, although normally each whorl is stamped with its own individuality, it is easy to imagine, in accordance with the principles of evolution, that others may partake of it; and so the characteristic features peculiar to one whorl can transcend its limits, and influence others as well. Beyond some such interpretation as this, I do not think it is possible to go. In saying that a fibro-vascular cord can "give rise" to a sepal, or petal, or other organ, I need hardly remind the reader that I am only speaking metaphorically, in describing what one observes in studying the anatomy of flowers. CHAPTER XXX. * PHYLLODY OF THE FLORAL WHORLS. VIRESCENCE AND FOLIACEOUS CONDITIONS-SEPALS, PETALS, AND STAMENS. The last changes to be described, which are common to all the members of a flower, are virescence, when they retain their normal forms, but are simply green; and foliaceous conditions, when they assume more or less a truly leaf-like form. Dr. Masters has given descriptions† of several of each kind of floral members as well as of foliaceous bracts, to which I must refer the reader for details. There are certain particulars, however, to which I would especially draw attention as throwing light upon the ordinary structure of floral whorls, and especially that of ovules. Taking the Alpine Strawberry as an illustrative case, the petals, stamens, and carpels are often more or less foliaceous; but the petals retain a palmate venation, though the three leaflets of the ternate leaf are pinnately nerved (Fig. 83, a, b). In the case of stamens the connective may be foliaceous, as in Petunia (Fig. 81); also in the Alpine Strawberry (Fig. 83, a) and in the "Green Rose the anthers are often persistent on either edge of a leaf-like intermediate part * The abnormal assumption of a leaf-like character. Ibid., p. 254. |