Hypertrophy, whatever form it may assume, may be so slight as not perceptibly to interfere with the functions of the part affected, or it may exist to such an extent as to impair the due exercise of its office. It may affect any or all parts of the plant, and is generally coexistent with, if not actually dependent on, some other malformation. Thus, the inordinate growth of some parts is most generally attended by deficiency in the size and number of others, as in the peripheral florets of _Viburnum_ or _Hydrangea_, where the corollas are relatively very large, and the stamens and pistils abortive. CHAPTER I. ENLARGEMENT. A swollen or thickened condition (_renflement_) is usually the result of a disproportionate formation of the cellular tissue as contrasted with the woody framework of the plant. We see marked instances of it in cultivated carrots and turnips, the normal condition of the roots or root-stocks in these plants being one of considerable hardness and toughness, and their form slender, tapering, and more or less branched. The disproportionate development of cellular tissue is also seen in tubers and bulbs, and in the swollen stems of such plants as _Echinocactus_, _Adenium obesum_, some species of _Vitis_, &c. So, too, the upper portion of the flower-stalk occasionally becomes much dilated, so as ultimately to form a portion of the fruit. But it is not necessary to give farther illustrations of this common tendency in some organs to become hypertrophied. As a result of injury from insects or fungi, galls and excrescences of various kinds are very common, but their consideration lies beyond the scope of the present work. [Illustration: FIG. 200.--_Pelargonium_, one branch of which was hypertrophied.] =Enlargement of axile organs.=--All the species of _Pelargonium_, _Geranium_, _Mirabilis,_ as well as those of _Caryophylleae_ and other orders, have tumid nodes as a normal occurrence. In the genus _Pelargonium_ this swelling is sometimes not confined to the nodes, but extends to the interspaces between them, _e.g._ _P. spinosum_. This condition, which happens as a natural feature in the species just named, may also occur as an exceptional thing in others. The author is indebted to Dr. Sankey for a branch of _Pelargonium_ which was thus thickened, the remaining branches not being in any way affected. The leaves on the swollen branch were smaller than the others, and their stalks more flattened. There was, in this instance, no trace of fungus or insect to account for the swelling of a single branch, which might, therefore, be due to bud-variation, perhaps to reversion to some ancestral form. The repeated cross fertilisations to which Pelargoniums have been subjected render this hypothesis not an improbable one. As an accompaniment to a spiral torsion of the woody fibres, this distension of the stem is frequently met with, as in _Valeriana_, _Dipsacus,_ &c. (See Spiral Torsion.)