[507] 'Mém. Acad. Toulouse,' t. 6, 1862.
[508] 'D. C. Prod.,' ii, pp. 172, 187.
[509] Richard, "Obs. sur les bulbilles des Crinum;" 'Ann. Sc. Nat.,' t. ii, p. 12. pl. i, fig. 1, 2. See also A. Braun, "Mémoire sur les graines charnues des Amaryllidèes," &c.; 'Ann. Sc. Nat.,' 1860, vol. xiv, p. 1, tab. 1.
CHAPTER II.
ELONGATION.
The class of cases coming under this head are sufficiently indicated by the name. There are many instances of this phenomenon occurring under different conditions, which, though unusual, can hardly be called abnormal, such, for instance, as the great lengthening of roots in their search for water, the excessive elongation that takes place in plants when grown at a distance from the light, in their endeavour to attain to which they become, as gardeners phrase it, "drawn." A similar result is brought about in forests or plantations, where long spars are required, by allowing the trees to grow very close to each other, so as to prevent the lateral extension of the branches. When plants grow in running water their roots, stems, and sometimes their leaves, become excessively elongated, as in Ranunculus fluitans, the flower-stalks of Valisneria spiralis, &c. These are cases of variation rather than of malformation, but are none the less curious, or sometimes perplexing; thus, Lapeyrouse described, in his 'Supplement à la flore des Pyrenées,' p. 27, under the name Potamogeton bifolium, a plant which Mr. Bentham subsequently discovered to be nothing but a flowerless variety of Vicia Faba distorted by its growth in water.[510]
Elongation of the root.—This, as already remarked, is more often a variation than a malformation, and is usually due to the presence of water at a distance necessitating growth at the extremities of the root, or to the presence of some obstacle, such as a stone, to avoid which the root elongates till it has passed the obstruction. Occasionally in Crocus corms some of the fibrils may be met with much lengthened and thickened, and invested with a fleshy sheath. It is not certain, however, that these structures are roots; possibly, nay probably, they may be processes from the stem thrust downwards into the soil, similar to the formations already described in the tulip (p. 85, fig. 39).
Elongation of the inflorescence.—Under this heading it is necessary to consider lengthening of the common rachis in the case of an aggregate inflorescence, and lengthening of the individual flower-stalks, whether they be solitary or portions of a multiple inflorescence. The two phenomena may occur together, but they are quite as often independent one of the other. Thus, among Umbelliferæ the umbels are occasionally met with supported on unusually long stalks, while the pedicels of the individual flowers may or not be increased in length; so also with some of the Composites, or the heads of flowers of some Leguminosæ, Trifolium repens, &c. &c.
Another illustration of the sort is that recorded by M. Fournier, wherein the usually umbellate inflorescence of Pelargonium was, through the lengthening of the main stalk, transformed into a raceme. Among Composites a similar change may sometimes be met with.
MM. Clos and De Schönefeld have recorded the existence of a variety of the sweet chestnut (Castanea)in which the female catkins were as long, and bore nearly as many flowers, as the male spikes. This is stated to be of constant occurrence in some localities, and to be accompanied by a diminished size of the fruits. A similar elongation has been observed in the case of the walnut, catkins of which have been seen bearing thirty to thirty-five large nuts.[511]