the leaf. This state is sometimes present to an
extreme degree, as in some varieties of shrubs (_Crataegus_, _Robinia_,
&c.) cultivated for their singularly tortuous branches.

[Illustration: FIG. 170.--Portion of the culm of a _Juncus_, bent
irregularly.]

[Illustration: FIG. 171.--Portion of a branch of _Crataegus oxyacantha_,
var. _tortuosa_.]

Such cases as those just mentioned, however, are but slightly irregular
compared to others in which the deformity exists to such an extent that
the traces of the ordinary mode of growth are almost obliterated. M.
Moquin-Tandon[353] alludes to a case of this kind in a species of pine
(_Pinus_), in which a branch ended in four unequal divisions, which were
strongly curved from without inwards, then became united in pairs, these
latter in their turn blending into a single mass.

In the case of some beeches growing in the forest of Verzy, near Rheims,
the trunks of the trees are contorted in every direction, and, at a
height of from fifteen to twenty feet, a number of branches are also
given off, also much contorted, and occasionally intergrafted, so that
it seems as if a heavy weight had been placed on the trees and literally
flattened them. Similar malformations may occasionally be met with in
the branches of the oak, and commonly in the weeping ash.

M. Fournier[354] mentions the stems of _Ruscus aculeatus_ rolled in a
circle, others twisted spirally.

The phenomenon is not confined to woody plants, but has been met with in
chicory, in _Antirrhinum_, and other herbaceous species.

It is very difficult in some cases to separate these instances of
irregular torsion from those in which the twisting takes place in a more
or less regular spiral direction. In the former case the fibres of the
plant are only indirectly involved, but in the latter the fibres
themselves are coiled spirally from right to left, or _vice versa_
(spiral torsion), while not unfrequently both conditions may be met with
at the same time.

The leaves also are subject to similar deformities, of which a notable
illustration has been recorded in the case of the date palm, _Phoenix
dactylifera_, originally observed by Goethe, and figured and described
by Jaeger;[355] the leaves are folded and twisted in every direction, in
consequence of the fibrous band or cord which surrounds the leaves, and
which generally breaks as the leaflets increase in size, remaining from
some cause or other unbroken, and thus se