Vegetable Teratology: An Account of the Principal Deviations from the Usual Construction of PlantsMasters, Maxwell T. (Maxwell Tylden)
Science
Vegetable Teratology: An Account of the Principal Deviations from the Usual Construction of Plants
Masters, Maxwell T. (Maxwell Tylden)
Plants -- Abnormalities
In a species of _Geranium_ recently examined the sepals presented
themselves in the form of three-lobed leaflets; so in fuchsias and in
_Epilobium hirsutum_ the sepals occasionally are not distinguishable
from ordinary leaves (fig. 130). In roses, the change in question is a
very frequent accompaniment of prolification (fig. 129). In the peach
also this replacement of the sepals is sometimes carried to such an
extent, that five perfect, bistipulate leaves occur in the place of the
calyx, but when this is the case it usually happens that the pistil is
abortive.
[Illustration: FIG. 130.--Fuchsia, with one of the sepals leaf-like.]
De Candolle[256] figures a curious instance wherein the pappus of
_Podospermum laciniatum_ was replaced by five linear, foliaceous lobes.
A similar change has been noticed in other composites, as in _Tragopogon
pratense_. Engelmann mentions as subject to this hypertrophy of the
pappus, as it may be termed, _Scorzonera octangularis_ and _Senecio
vulgaris_. Wigand has observed a similar transformation in a species of
_Centranthus_ (_Valerianaceae_).
In some cases the phyllody of the sepals has a special interest, as
bearing on the question whether what is termed calyx-tube is or is not a
portion of the calyx, and whether the sepals are modifications of the
blade or of the sheath of the leaf. Thus in the primrose the phyllodic
sepals seem to show clearly that the sepals are in that plant of a
laminar nature (fig. 131). The so-called calyx-tube of roses is
elsewhere alluded to. The leaf-like organs sometimes seen at the apex of
a cucumber would seem to support the view that there was really a
calyx-tube in _Cucurbitaceae_ adherent to the carpels. It is also shown
in the cut, fig. 132, borrowed from the 'Gardeners' Chronicle,' 1859,
p. 654.
[Illustration: FIG. 131.--Primrose. Calyx of foliaceous segments.]
[Illustration: FIG. 132.--Leafy calyx of melon.]
Under ordinary circumstances, the sepals may be considered as the
representatives of the sheath of the leaf (cataphyllary) or of the blade
(euphyllary), the arrangement of the veins being different in the two
cases; thus, in the vagina or sheath, there are generally several large
veins of about equal size, either convergent towards the apex, or
divergent; on the other hand, in the blade, there is usually but one
central vein, the midrib, larger than the rest, and the smaller veins
come off at a less acute angle, and are more reticulated.[257]
Now, when phyllomorphy occurs in sepals which ordinarily are vaginal, it
is obvious that the case is one, not merely of increased relative
growth, but also of the appearance or development of an organ habitually
suppressed; on the other hand, when phyllomorphy occurs in sepals which
usually are laminar in form and nervation, the case is one of unusual
growth or hypertrophy, and not of the development of an organ habitually
suppressed, so that the amount of change is greater in the former than
in the latter instance.
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