In some parts of Holland where madder is cultivated a similar deformation is particularly frequent. The leaves, however, are not always grouped in the way in which they were described by M. Duchartre, but more commonly form a single continuous line; when arranged in leaf-whorls it generally happens that some of the leaves are turned downwards, while others are erect. It has been said that this condition occurs particularly frequently in plants growing in damp places. It is certainly true that spiral torsion of the stem is specially frequent in the species of _Equisetum_, most of which grow in such spots. In these plants either the whole of the upper part of the stem is thus twisted, or a portion only: thus Reinsch[360] cites a case in _Equisetum Telmateia_, where the upper and lower portions of the stem were normal, while the intermediate portion was twisted spirally. In this instance the whorl next beneath the spiral had twenty-eight branchlets, and that immediately above it thirty. Along the course of the spire there were two hundred and three; dividing this latter number by the mean of the two preceding, it was seen that the spire included the constituents of seven ordinary verticils. [Illustration: FIG. 173.--Stem of _Galium_ spirally twisted. From a specimen communicated by Mr. Darwin.] Here also may be mentioned a curious bamboo, the stem of which is preserved in the British Museum, and in which the internodes, on the exterior, and the corresponding diaphragms and cavities within are spiral or oblique in direction. The root is also subject to the same malformation, the inducing cause being usually some obstruction to downward growth, as when a plant has been grown in a small pot, and becomes, as gardeners say, pot-bound. [Illustration: FIG. 174.--Showing "pot-bound" root twisted spirally (from the 'Gard. Chron.,' 1849).] The axial portion of the flower, the thalamus, is also occasionally twisted in a spiral direction, the lateral parts of the flower being in consequence displaced. Morren spoke of this displacement of the floral organs as "speiranthie."[361] Morren draws a distinction between spiral-torsion or spiralism and the less regular torsion spoken of in the preceding section; in the former case not only is the axis twisted, but its constituent fibres also. The condition in question in some cases seems to be inherited in the seedling plants. The following is a list of the plants in which spiral torsion of the stem or branches has been most frequently observed. (See also under Fasciation and Contortion.)