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.)
- Hesperis matronalis.
- Dianthus barbatus.
- Pyrus Malus.
- torminalis.
- Cercis siliquastrum!
- Punica Granatum.
- Robinia pseudacacia!
- Rubia tinctorum.
- Dipsacus fullonum!
- pilosus.
- Gmelini.
- Scabiosa arvensis.
- *Valeriana officinalis!
- dioica!
- Galium aparine!
- *Mollugo!
- verum!
- Hippuris vulgaris!
- Veronica spicata.
- longifolia.
- Hyssopus officinalis.
- Thymus Serpyllum.
- Lamium purpureum!
- Dracocephalum speciosum.
- Mentha aquatica.
- Mentha viridis.
- Fraxinus vulgaris!
- Sambucus nigra.
- Zinnia.
- Phylica.
- Beta.
- Rumex, sp.
- Ulmus campestris.
- Casuarina rigida.
- Abies excelsa!
- Lilium Martagon!
- candidum.
- *Asparagus officinalis!
- Sagittaria sagittifolia.
- Epipactis palustris.
- Triticum repens!
- Lolium perenne!
- Phleum pratense.
- Juncus conglomeratus!
- Scirpus lacustris.
- Equisetum Telmateia.
- limosum.
- fluviatile.
- arvense!
Among the more important papers relating to this subject may be mentioned:
Moquin-Tandon, 'El. Ter. Veg.,' p. 181. Kros, 'De Spira in plantis conspicua.' Morren, 'Bull. Acad. Roy. Belg.,' 1851, tom. xviii, part i, p. 27. Milde, 'Nov. Act. Acad. Leop. Carol. Nat. Cur., 1839. Ibid., vol. xxvi, part ii, p. 429, Equisetum. Irmisch, 'Flora,' 1858, t. ii, Equisetum. Vrolik, 'Nouv. Mem. Instit. Amsterdam,' Lilium. Schlechtendal, 'Bot. Zeit.,' xiv, p. 69, et v, p. 66. De Candolle, 'Organ. Veget., t. i, p. 155, tab. xxxvi, Mentha, &c. Alph. de Candolle, 'Neue Denkschr. Allg. Schweiz. Gesellschft.,' band v, tab. vi, Valeriana. Duchartre, 'Ann. Sc. Nat.,' ser. 3, vol. i, p. 292. 'Gardeners' Chronicle,' July 5, 1856, p. 452, c. ic. xylogr., spiral branches from Guatemala—tree not known.
Spiral twisting of the leaf is scarcely of so common occurrence as the corresponding condition in the stem. In Alstrœmeria it occurs normally, as also in some grasses. In the variety annularis of Salix babylonica the leaf is constantly coiled round spirally. A similar contortion occurs in a variety of Codiæum variegatum lately introduced from the islands of the South Seas by Mr. J. G. Veitch.
Fern fronds are occasionally found twisted in the same manner, e.g. Scolopendrium vulgare var. spirale.[362]