completely the appearance of petals, a singular appearance is afforded
by the presence of four wing-like processes emanating from the central
filaments, two on each side, so that the arrangement may be compared to
two sheets of paper folded in the centre and adherent in that situation,
though perfectly separate elsewhere, except sometimes at the top, where
they form a sort of hood. This change results from an imperfect petalody
of the anther; the two wings on each side of the central vascular cord
represent the front and back walls of an anther lobe, or rather of that
portion of the anther which, under ordinary circumstances, produces
pollen. In the malformed flowers no pollen is formed, at least in the
more complete states of the malformation, but the walls of the anther
lobe become preternaturally enlarged, and petaloid in texture and
appearance. This change occurs in some semi-double rhododendrons and
azaleas, in crocuses, and in a species of violet found at Mentone by Mr.
J. T. Moggridge.
There are numerous intermediate forms wherein the wing-like processes
may be traced all the way along the filament till they ultimately lose
themselves in the anther-lobes, with which they become continuous. In
some cases, as in _Crocus_ and _Rhododendron_, this is shown even more
clearly by the existence of two perfect pollen-sacs or quarter-anthers,
the remaining portions being petaloid and continuous with the dilated
filament. Not unfrequently these semi-petaloid stamens adhere to the
fronts of the petals, and then it appears, at a first glance, as if
three organs were stuck together, one in front of another, while in
reality there are but two.[305] (See _ante_, p. 35, fig. 12.)
[Illustration: FIG. 155.--Four-winged filaments of _Rhododendron_.]
The change in the anther, above alluded to, must not be mistaken for
that far more common one in which only a small portion of the anther
becomes petaloid, forming a sort of lateral wing or appendage to the
polliniferous portion, as happens normally in _Pterandra_, and is common
in some double fuchsias. In this latter instance there is but a single
wing, and the nature of the case is obvious.
Double flowers of _Orchidaceae_ generally arise from petalification of
the filaments, with or without other coincident changes. What makes
double flowers in this order the more interesting is the development, in
a petaloid condition, of some or all of those stamens which under
ordinary circumstances are wholly suppressed, so that the morphological
structure of the flower, at first a matter of theory, becomes actually
realised. Fig. 156 is a diagram showing the presence of two additional
labella within the ordinary one in a species of _Catasetum_, and
representing two petaloid stamens, thus evidently completing the outer
staminal whorl, of which there is usually but a single representative
(see Peloria, Multiplication, Prolification). In some of these double
orchids it is, however, necessary not to confound a petaloid condition
of the existing column with the development of usually suppressed
stamens in a petaloid form. Thus, in _Lycaste Skinneri_ the column is
frequently provided with two petal-like wings, which might readily be
supposed to be two stamens of the inner whorl adherent to the column; a
little attention, however, to the relative position of these
adventitious wings is generally sufficient to enable the observer to
ascertain the true nature of the appearance.[306]
[Illustration: FIG. 156.--Diagram of flower of _Catasetum_, with two
labella.]
Some forms of duplicate or hose in hose corollas are apparently due, not
so much to the formation of a second corolla within the first, as to the
presence of an inner series of petal-like stamens, which, by their
cohesion, form a second pseudo-corolla within the first. The staminal
nature of this pseudo-corolla is inferred from the occasional presence
of anthers on it.[307] In _Datura fastuosa_, as well as in _Gloxinia_, a
pseudo-corolla of this kind sometimes occurs with the addition of a
series of petaloid stamens attached to its outer surface.[308]
When the petalody specially affects the anther-lobes, as in _Arbutus_,
_Petunia_, _Fuchsia_, _&c._, the venation of the petal-like portion is
very frequently laminar, thus tending to show that the anther is in
such cases really a modification of the blade of the leaf; but as, on
the other hand, we often find petal-like filaments bearing pollen-sacs
on their sides, it is clear that we must not attribute the formation of
pollen to the blade of the leaf only, but we must admit that it may be
formed in the filament as well.[309]
[Illustration: FIG. 158.--Portion of a double columbine (_Aquilegia_),
showing petalody of the connective.]
[Illustration: FIG. 159.--Petaloid stamens, _Hibiscus_.]
Petalody of the connective is of less frequent occurrence than the
corresponding change in the other portions of the stamen. It may be seen
in some forms of double columbine,[310] in which the connective forms a
tubular petal or nectary, and in double petunias and fuchsias. When it
occurs, the true anther-lobes are usually atrophied, and little or no
pollen is formed.
An occurrence of this nature in _Tacsonia pinnatistipula_, in
conjunction with the partial detachment of the stamens from the
gynophore, led Karsten to establish a genus which he called
_Poggendorffia_.[311]
From the subjoined list of genera in which petalody of the stamens, in
some form or other, has been observed, it will be seen that it happens
more often in plants with numerous distinct organs (Polypetalae,
Polyandria, Polygynia, &c.) than in other plants with a smaller number
of parts, and which are more or less adherent one to the other. The
tendency to petalification is, moreover, greater among those plants
which have their floral elements arranged in spiral series, than among
those where the verticillate arrangement exists; and in any given
flower, if the stamens are spirally arranged while the carpels are
grouped in whorls, the former will be more liable to petalody than the
latter, and _vice versa_. It has been before remarked, that this
condition is far more common in plants whose petals, &c., have straight
veins, like those in the sheath of a leaf, than in those the venation of
which is reticulate, as in the blade of the leaf. It must also be
remembered that in the same genus, even in the same species, different
kinds of doubling occur. Familiar illustrations of this are afforded in
the case of anemones, columbines, fuchsias, and other plants.
The existence of "compound stamens" in some flowers, as pointed out by
Payer, and others, and the researches of Dr. Alexander Dickson, confer
additional importance on the subject of petalody, and necessitate the
examination of double flowers with special reference to these compound
stamens, and to the order of their development.[312] The presence of
these compound stamens affords a satisfactory explanation of the
appearance in some double _Malvaceae_, wherein the tufts of adventitious
petals are very liable to be mistaken for buds, produced by axillary
prolification in the axils of the petals, but which are in reality
compound and petaloid stamens. At other times, however, true axillary
prolification exists in these flowers; but then the supplemental florets
have always a calyx, which is wanting in the other instances.
Petalody of the stamens has been met with most frequently in the
following genera:
*Ranunculus!
*Anemone!
*Papaver!
*Clematis!
*Hepatica!
*Ficaria!
Thalictrum.
*Caltha!
*Trollius!
*Nigella!
*Aquilegia!
*Delphinium!
*Adonis!
*Paeonia!
*Nelumbium!
*Nymphaea!
*Berberis!
*Papaver!
*Chelidonium!
Sanguinaria.
Podophyllum.
*Mathiola!
*Cheiranthus!
*Iberis!
*Cardamine!
*Hesperis.
*Barbarea!
*Sinapis!
*Brassica!
*Helianthemum!
*Viola!
*Dianthus!
*Saponaria!
*Lychnis!
*Silene!
*Sagina!
*Hibiscus!
*Althaea!
*Malva!
AEsculus!
*Geranium!
*Pelargonium.
*Tropaeolum!
Oxalis!
*Impatiens!
*Camellia!
Thea!
Trifolium!
Medicago!
*Ulex!
Spartianthus.
Clitoria.
Pisum!
Orobus!
Genista!
Spartium!
Cytisus!
Anthyllis.
Coronilla.
Lotus!
*Rosa!
*Kerria!
*Spiraea!
*Fragaria!
*Potentilla!
*Crataegus!
Cydonia.
*Pyrus!
Eriobotrya!
*Amygdalus!
*Prunus!
*Myrtus!
*Punica!
*Philadelphus!
*Deutzia!
*Fuchsia!
Godetia!
Clarkia!
Portulaca!
Ribes!
Saxifraga!
Daucus.
Ixora.
Serissa!
Gardenia!
Lonicera!
Sambucus.
Viburnum.
Scabiosa.
*Campanula!
Platycodon!
Calluna!
Azalea!
Rhododendron!
*Arbutus!
*Erica!
*Anagallis!
*Primula!
*Jasminum!
Syringa!
*Vinca!
*Nerium!
Allamanda!
Tabernaemontana.
*Calystegia!
Convolvulus!
Ipomoea.
*Datura!
*Petunia!
Solanum!
Orobanche.
Gentiana.
Mimulus.
*Antirrhinum!
Gratiola!
*Digitalis!
*Linaria!
Veronica!
Calceolaria!
Achimenes.
Gloxinia!
Clerodendron!
Bignonia.
Cyclamen!
Mirabilis.
Laurus!
Gladiolus!
Crocus!
Iris!
*Galanthus!
Leucojum!
Sternbergia!
Hippeastrum.
*Narcissus!
*Orchis!
Catasetum!
Hydrocharis.
Asphodelus.
*Tulipa!
Scilla.
*Convallaria!
Fritillaria!
*Lilium!
*Hyacinthus!
*Polianthes!
*Hemerocallis!
*Colchicum!
*Sagittaria!
*Tradescantia!
Commelyna!
Tofieldia.
=Petalody of the pistils.=--Taken by itself, this is much less common
than the corresponding change in the stamens. It generally affects the
style and stigma only, as happens normally in _Petalostylis_, _Iris_,
&c., but this is by no means always necessarily the case. In some of the
cultivated varieties of _Anemone_ and _Ranunculus_ all the parts of the
flower remain in their normal state, except the pistils, which latter
assume a petaloid appearance.
Many of the double flowers owe their peculiar appearance to the
combination of the following appearances--a petal-like form of the
stamens, increase in the number of these organs and similar changes
affecting the pistils, and is applied to several distinct conditions. If
in any given flower all the stamens and all the pistils become wholly
petaloid, no pollen is formed, and of course no seeds can be produced,
but this very rarely happens, as usually some pollen is produced, and
some ovules capable of being fertilised are developed.
In double flowers of _Primula sinensis_ it frequently happens that the
capsule is either partially leafy or partly petal-like; in either case
the fruit is open at the extremity, and often destitute of the style and
stigma. It is, however, doubtful if the ovules can be fertilised in
these flowers.
The following list comprises the names of those genera in which this
change has been most frequently observed, independently of corresponding
alterations in the stamens, but it is more usual for both sets of organs
to be similarly affected.
*Ranunculus!
*Anemone!
Nigella.
*Papaver!
*Dianthus!
Saponaria!
Viola!
Camellia!
Alcea.
Hibiscus!
Amygdalus!
Lonicera!
Scabiosa.
AEschynanthus!
Primula!
=Petalody of the ovules.=--The principal changes which occur in the
ovule have already been alluded to at pp. 262-272; it may here be
stated, however, that the ovules are occasionally represented by small
stalked petal-like structures. This happens with especial frequency
among _Cruciferae_.[313]
=Petalody of the accessory organs.=--A petaloid condition of the disc,
of the scales, or other excrescences from the axis or from the lateral
portions of the flower, is of frequent occurrence, though it is but
rarely that the change is of any great importance in a morphological
point of view. C. Morren has given the name adenopetaly to a case
wherein one of the glands at the base of the petals in _Lopezia_ was
replaced by a petal.[314] A similar change may be seen in the double
Oleander.
=Staminody of the bracts.=--An instance of this has been already alluded
to in _Abies excelsa_, as observed by Prof. Dickson, and in which some
of the bracts were seen assuming the form and characteristic of the
stamens see _ante_: p. 192. Signor Licopoli met with a similar
substitution of anthers for bracts in _Melianthus major_.[315]
=Staminody of the sepals and petals.=--In the first named this is of
very rare occurrence. M. Gris has recorded an instance in _Philadelphus
speciosus_[316] which appears to be the only case on record. The
corresponding change in the case of the petals is far more common. De
Candolle cites in illustration of this occurrence flowers of the common
haricot, in which the alae and carina of the corolla were thus
changed.[317] There is in cultivation a form of _Saxifraga granulata_
wherein the petals are replaced by stamens, so that there are fifteen
stamens. A similar change has been observed in _Capsella
bursa-pastoris_.
Cramer figures and describes a stamen occupying the place of a petal in
_Daucus Carota_.[318] Turpin[319] describes a similar occurrence in
_Monarda fistulosa_, in which the lower lip terminated in an anther, but
this may have been a case of adhesion. Moquin cites from Chamisso,
_Digitalis purpurea_, and from Jussieu, _Asphodelus ramosus_, as having
presented this change, and Wiegmann[320] has seen anthers developed on
the awns of _Avena chinensis_. In semi-double flowers of _Ophrys
aranifera_ and _Orchis mascula_, the lateral petals are occasionally
partially antheroid, and others occur in which two of the outer series
of stamens, which are ordinarily suppressed, are present, but in a
petaloid state. Reichenbach[321] figures an illustration of this change,
and also Moggridge.[322]
=Staminody of the pistils.=--The existence of this change has been
denied by several authors, nevertheless, it is of sufficiently common
occurrence. Alexander Braun notices the transformation of pistils into
stamens in Chives (_Allium Scorodoprasum_), and in which three stamens
appeared in the place of as many pistils, and had extrorse anthers,
while the six normal anthers are introrse. In the horse-radish
(_Armoracia rusticana_), two of the carpels are frequently converted
into stamens, while two other organs absent from the normal flower make
their appearance as carpels. Roeper has observed this phenomenon in
_Euphorbia palustris_,[323] and in _Gentiana campestris_.[324] In these
examples one of the carpels was apparently absent, and its place
supplied by an anther. Roeper has also mentioned a balsam with a
supernumerary stamen occupying exactly the position of a carpel.[325]
Agardh has observed a similar thing in a hyacinth, one half of the fruit
of which contained seeds, and the other half, anthers. B. Clarke
mentions an instance in _Mathiola incana_ in which the carpels were
disunited, and antheriferous at the margin.[326]
The passage of pistils to stamens in willows has been frequently
remarked, as in _Salix babylonica_, _silesiaca_, _cinerea_, _Caprea_ and
_nigricans_. One of the most curious illustrations of this
transformation in this genus is given by Henry and Macquart (Erst.
Jahrb. des bot. Vereines am m. et n. Rhein., 1837). In the flowers in
question the series of changes were as follows:--first, the ovary opened
by a slit, and then expanded into a cup; next, anther-cells were
developed on the margin of the cup, with stigmas alternating with them,
the ovules at the same time disappearing; lastly, the margin became
divided, and bore three perfect anthers, which in the more perfect
states were raised on three filaments.
_Campanula persicifolia_, _C. rapunculoides_, and _C. glomerata_ have
been observed to present an anther surmounting the pistil.[327] Double
tulips often present this change, and a like appearance has been
observed in _Galanthus nivalis_, and _Narcissus Tazetta_.
Moquin mentions the existence of this condition in a female plant of
maize, some of the pistils of which were wholly or partially converted
into anther-like organs. Mohl has recorded an analogous malformation in
_Chamaerops humilis_, and in which the three carpels were normally
formed, and only differed from natural ovaries in this, that along the
two edges of the ventral suture there was a yellow thickening, which a
cross section of the ovary showed to be an anther-lobe filled with
pollen.[328]
In _Tofieldia calyculata_ a similar substitution of a stamen for a
carpel has been observed by Klotsch,[329] and Weber[330] gives other
instances in _Prunus_ and _Paeonia_. Corresponding alterations may be met
with in cultivated tulips, in the cowslip and other plants. In most of
the above cases the transmutation has been perfect, but in quite an
equal number of cases a portion only of the carpel is thus changed,
generally the style or the stigma; thus Baillon describes the stigmas of
_Ricinus communis_ as having been in one instance antheriferous.[331]
Moggridge figures a flower of _Ophrys insectifera_ in which the
rostellate process was replaced by an anther.[332]
Mohl remarks that the change of pistils into stamens is more common in
monocarpellary pistils than it is in those which are made up of several
carpels. It seems clear that in this transformation the lobes of the
anther and the development of pollen have no relation to the production
of ovules.
=Staminody of the accessory organs of the flower.=--The scales that are
met with in some plants, either as excrescences from the petals, or as
imperfect representatives of stamens or other organs, are occasionally
staminoid; thus the scales of _Saponaria officinalis_, of _Silene_,
_Nerium Oleander_, the rays of _Passiflora_, the corona of _Narcissus_,
have all been observed occasionally to bear anthers.[333] In the case of
_Narcissus_ the loose spongy tissue of the corona seems to have the
nearest analogy to the anther-lobes, while the prolonged connective is
more like the ordinary segments of the perianth in texture. The species
in which this change may most frequently be observed are, _N. poeticus_,
_N. incomparabilis_, and _N. montanus_.
M. Bureau found in some flowers of _Antirrhinum majus_ two petal-like
bodies standing up in front of, or opposite to the two petals of the
upper lip,[334] and similar developments in which each of the two
adventitious segments are surmounted by an anther may be met with
frequently. It does not follow because these organs bear anthers that
they are morphologically true stamens. They are really scales, &c.,
taking on themselves accidentally the characters proper to stamens.
=Pistillody of the perianth.=--The passage of the segments of the
perianth into carpels has been observed frequently in _Tulipa
Gesneriana_, the change in question being generally attended by a
partial virescence. M. Gay is said by Moquin to have observed a flower
of _Crocus nudiflorus_ in which the segments of the perianth were cleft
and fringed at the same time, so that they presented the appearance of
the stigmas.
[Illustration: FIG. 160.--Flower of tulip, allowing vertical attachment
of a leaf, and also the existence of ovules on the margins of the
segments of the perianth. Some of the parts are removed.]
=Pistillody of the sepals.=--In some double flowers of the garden pea
communicated by Mr. Laxton, among other peculiarities was a
supernumerary 5-6-leaved calyx, some of the segments of which were of a
carpellary nature, and bore imperfect ovules on their margins, while at
their extremities they were drawn out into styles.[335]
=Pistillody of the stamens.=--This change whereby the stamens assume more
or less the appearance of pistils is more commonly met with than is the
metamorphosis of the envelopes of the flower into carpels. In some cases
the whole of the stamen appears to be changed, while in others it is the
filament alone that is altered, the anther being deficient, or
rudimentary; while, in a third class of cases, the filament is
unaffected, and the anther undergoes the change in question. In those
instances in which the filament appears to be the portion most
implicated, it becomes dilated so as to resemble a leaf-sheath rather
than a leaf-stalk, as it does usually.
One of the most curious cases of this kind is that recorded in the
'Botanical Magazine,' (tab. 5160, f. 4) as having occurred in _Begonia
frigida_ already alluded to, and in which, in the centre of a male
flower, were four free ovoid ovaries alternating with as many stamens.
In the normal flowers of this plant, as is well known, the male flowers
have several stamens, while in the female flowers the ovary is strictly
inferior, so that, in the singular flower just described, the perianth
was inferior instead of being superior, as it is usually. It should be
added also that the perianth in these malformed flowers was precisely
like that which occurs ordinarily in the male flowers.
[Illustration: FIG. 161.--Supernumerary carpels in the orange, arising
from substitution of pistils for stamens.]
In some varieties of the orange, called by the French "bigarades
cornues," the thalamus of the flower, which is usually short, and
terminated by a glandular ring-like disc, is prolonged into a little
stalk or gynophore, bearing a ring of supernumerary carpels. These
carpels are isolated one from another, and are formed by the
transformation of the filaments of the stamens.[336]
The additional carpels in the case of the apple of St. Valery, in which
the petals are of a green colour, like the sepals, are by some
attributed to the transformation of the stamens into carpels. These
adventitious carpels frequently contain imperfect ovules and form a
whorl above the normal ones. (See _Pyrus dioica_ of Willdenow.)[337] A
similar change occasionally happens in the stamens of _Magnolia
fuscata_, while in double tulips this phenomenon is very frequent, and
among them may be found all stages of transition between stamens and
pistils, and many of the parts combining the characters of both.[338]
Dunal and Campdera have described flowers of _Rumex crispus_, with seven
pistils, occupying the place of as many stamens.
[Illustration: FIG. 162.--Substitution of carpels for stamens in
_Papaver_.]
In _Papaver bracteatum_ a considerable number of the stamens sometimes
become developed into pistils, especially those which are nearest to
the centre of the flower, and in these flowers the filaments are said to
become the ovaries, while the anthers are curled so as to resemble
stigmas. A similar change is not infrequent _Papaver somniferum_.
Goeppert, who found numerous instances of the kind in a field near
Breslau, says the peculiarity was reproduced by seed for two years in
succession.[339] Wigand ('Flora,' 1856, p. 717) has noticed among other
changes the pistil of _Gentiana Amarella_ bearing two sessile anthers.
_Polemonium caeruleum_ is another plant very subject to this change.
Brongniart[340] describes a flower of this species in which the stamens
were represented by a circle of carpels united to each other so as to
form a sheath around the central ovary. By artificial fertilization M.
Brongniart obtained fertile seeds from the central normal ovary as well
as from the surrounding metamorphosed stamens.
_Cheiranthus Cheiri_ has long been known as one of the plants most
subject to this anomaly. De Candolle even mentions it in his 'Prodromus'
as a distinct variety, under the name of _gynantherus_. Brongniart (loc.
cit.) thus refers to the _Cheiranthus_:--"Sometimes these six carpellary
leaves are perfectly free, and in this case they spread open, presenting
two rows of ovules along their inner edges, or these edges maybe
soldered together, forming a kind of follicle like that of the
columbine; at other times, these staminal pistils are fused into two
lateral bundles of three in each bundle, or into a single cylinder which
encircles the true pistil. In a third set of cases these outer carpels
are only four in number, two lateral and two antero-posterior, all fused
in such a manner as to form around the normal pistil a prism-shaped
sheath, with four sides presenting four parietal placentae, corresponding
to the lines of junction of the staminal carpels."
In the accompanying figures (fig. 163, _a-d_) the nature of this change
is illustrated. In some of the specimens it is easy to see that the two
shorter stamens undergo the change into carpels later and less perfectly
than the four longer ones, and not infrequently the outer pair are
altogether absent. In most of the flowers of this variety the petals are
smaller and less perfectly developed than usual.[341]
[Illustration: FIG. 163.--_Cheiranthus Cheiri_, var. _gynantherus_. _a._
Sepals and petals removed to show carpellodic stamens. _b._ The same
laid open. _c._ Transverse section. _d._ Plan of flower with four
carpel-like stamens, &c.]
In _Lilium tigrinum_, some specimens of which were gathered by Mr. J.
Salter, in addition to various degrees of synanthy and other changes,
some of the stamens were developed in the form of carpels, adherent by
their edges so as to form an imperfect tube or sheath around the normal
pistil. Fig. 164 shows one of the intermediate organs from these
flowers, in which half the structure seems devoted to the formation of
ovules, while the other half bears a one-celled anther. Lindley[342] has
also described a case of this kind in a species of _Amaryllis_.
[Illustration: FIG. 164.--Structure half anther, half carpel, _Lilium_.]
In _Saxifraga crassifolia_ it sometimes happens that mixed with the
stamens, and originating with them, are a number of distinct and
perfectly formed carpels, wholly separated from the normal carpels, in
the centre of the flower. In this particular instance there is usually
no intermediate condition between the stamen and the pistil.
Guillemin[343] also describes a transformation of the stamens into
carpels in _Euphorbia esula_.
When the anther is involved it may be only partially so, or almost the
whole organ may be transformed. As instances of very partial change may
be cited the passage of the connective into a stigma in _Thalictrum
minus_, or the passage of the points of the anthers into imperfect
styles in some species of bamboo.[344]
In _Rosa arvensis_ similar transformations have been observed of a
slightly more complex character than those just mentioned, and passing
into more important changes, especially to the formation of pollen
within ovules, formed on the edges of an open carpellodic anther (see p.
186).
Mr. Berkeley has recorded an analogous case in a gourd in which the
stamens bore numerous ovules (p. 200), and Baillon describes another
gourd in which certain fleshy appendages surrounding the androecium
were provided with ovules.[345]
Payer, in his 'Organogenie,' p. 38, mentions a stamen of _Dionaea_
bearing not only an anther, but likewise an ovule.
_Sempervivum tectorum_ and _S. montanum_, have long been noticed as
being very prone to present this change. Mohl[346] remarks that, in the
transformation of the stamens to the pistil in the common houseleek, the
filament of the stamen generally preserves its form, the anthers alone
undergoing change. At other times, however, the transformation takes
place at the same time, both in the filament and in the anther. When the
stamens are numerous some of them remain in their normal state, while
others, and especially the inner ones, undergo a change. Sometimes all
the stamens are changed simultaneously, while at other times some of
these organs may be found in which the anther is partially filled with
ovules, and partially with pollen.
In the accompanying figures (fig. 165, _a-h_) a series of intermediate
stages is shown between the ordinary stamen of _Sempervivum tectorum_
and the ordinary carpel, from which it will be seen that the filament is
little, if at all, affected, and that in those cases where there is a
combination of the attributes of the stamen and of the pistil in the
same organ the pollen is formed in the upper or inner surface of the
leaf-organ, while the ovules arise from the opposite surface from the
free edge, (_b_, _c_, _d_, _e_, _f_, _g_).
In a drawing made by the Rev. G. E. Smith of a malformed flower of
_Primula acaulis_, and which the writer has had the opportunity of
examining, the stamens are represented as detached from the corolla, and
their anthers replaced by open carpels, with ovules arising, not only
from their edges, but also from their surfaces, while the apex of the
carpellary leaf was drawn out into a long style, terminated by a
flattened spathulate stigma.
_Delphinium elatum_ is one of the plants in which this change has been
most frequently noticed.[347]
[Illustration: Fig. 165.--_Sempervivum tecotorum._ _a._ Normal stamen.
_h._ Normal carpel. _b_, _c_, _e_, _f_, _g_. Structure partly staminal,
partly carpellary. _d._ Transverse section through _c_, showing pollen
internally, ovules externally.]
In willows the change of pistils into staminal organs has been
frequently observed. In _Salix babylonica_ Prof. Schnizlein has
described various transition stages between the carpels and the stamens,
and in one instance, in addition to this change, a perfect cup-shaped
perianth was present, as happens normally in _Populus_[348]. Mr. Lowe
also records the conversion of stamens into ovaries in _Salix
Andersoniana_, and this by every conceivable intermediate
gradation.[349]
The following list will serve to show what plants are most subject to
this anomaly. It is difficult to draw any accurate inference from this
enumeration, but attention may be called to the frequency of this
occurrence in certain plants, such as the _Sempervivum_, the wallflower,
the poppy, and the heath. Why these plants should specially be subject
to these changes cannot be at present stated.
By the student of animal physiology such a change as above
described--equivalent to the substitution of an ovary or a uterus for a
testis--would be looked on as next to impossible; the simpler and less
specialised structure of plants renders such a change in them far more
easy of comprehension.
Thalictrum minus.
Delphinium elatum.
Magnolia fuscata.
Bocconia cordata.
*Papaver bracteatum!
* somniferum!
nudicaule.
Dionaea muscipula!
Barbarea vulgaris.
*Cheiranthus Cheiri!
Cochlearia Armoracia.
Tropaeolum majus.
Citrus Aurantium.
*Sempervivum tectorum!
montanum.
Begonia frigida!
Cucumis, sp.
Cucurbita Pepo.
Pyrus Malus.
Rosa arvensis!
Saxifraga crassifolia!
Myrtus, sp.
Campanula rapunculoides.
Polemonium caeruleum.
Gentiana Amarella.
*Erica Tetralix.
Stachys germanica.
Primula acaulis.
Rumex crispus.
*Salix, sp. plur.!
Euphorbia esula.
Glochidion.
Asphodelus ramosus.
Amaryllis.
Lilium tigrinum!
longiflorum.
*Tulipa Gesneriana!
var. cult. plurim.!
Hemerocallis.
Zea Mays.
Bambusa, sp.
=Pistillody of the ovule.=--An instance of this extraordinary
transformation in the carnation, as observed by the Rev. Mr. Berkeley,
is given at p. 268.
FOOTNOTES:
[295] 'Neue Denkschrift. Schweiz. Gesellsch.,' band v, p. 9.
[296] 'Bull. Acad. Belg.,' xix, part 2, p. 93.
[297] Schlechtendal, 'Linnaea,' ix, p. 737.
[298] Misbilld., 'Cult. Gewachs.,' p. 32.
[299] Linn., 'Phil. Botan.,' Sec. 120.
[300] 'Bull. Soc. Bot. France,' 1859, vol. vi, p. 199.
[301] Seemann's 'Journal of Botany,' vol. iii, p. 105; also Morren,
'Bull. Acad. Belg.,' vol. xx, part 2, p. 264.
[302] Morren, 'Bull. Belg.,' xviii, p. 503.
[303] 'Organ. Veg.,' t. i, p. 513.
[304] 'Bull. Acad. Roy. Belg.,' tome xvii; and Lobelia, p. 65.
[305] Masters, "On Double Flowers," 'Rep. Internat. Bot. Congress,'
London, 1866. p. 127.
[306] See also C. Morren, "Sur les vraies fleurs doubles chez les
Orchidees," 'Bull. Acad. Roy. Belg.,' vol. xix, part ii, 1852. p. 171.
[307] C. Morren, 'Bull. Acad. Belg.,' vol. xx, 1853, part ii, p. 284
(_Syringa_).
[308] 'Rep. Bot. Congress,' London, 1866, p. 135, t. vii, f. 14.
[309] Although it is generally admitted that the filament of the stamen
corresponds to the stalk of the leaf, and the anther to the leaf-blade,
yet there are some points on which uncertainty still rests. One of these
is as to the sutures of the anther. Do these chinks through which the
pollen escapes correspond (as would at first sight seem probable) to the
margins of the antheral leaf, or do they answer to the lines that
separate the two pollen-cavities on each half of the anther one from the
other? Professor Oliver, 'Trans. Linn. Soc.,' vol. xxiii, 1862, p. 423,
in alluding to the views held by others on this subject, concludes, from
an examination of some geranium flowers in which the stamens were more
or less petaloid, that Bischoff's notion as to the sutures of the anther
is correct, viz., that they are the equivalents of the septa of
untransformed tissue between the pollen-sacs. Some double fuchsias
('Gard. Chron.,' 1863, p. 989) add confirmation to this opinion. In
these flowers the petals were present as usual, but the stamens were
more or less petaloid, the filaments were unchanged, but the anthers
existed in the form of a petal-like cup from the centre of which
projected two imperfect pollen-lobes (the other two lobes being
petaloid). Now, in this case, the margins of the anther were coherent to
form the cup, and the pollen was emitted along a line separating the
polliniferous from the petaloid portion of the anther. This view is also
borne out by the double-flowered _Arbutus Unedo_, and also by what
occurs in some double violets, wherein the anther exists in the guise of
a broad lancet-shaped expansion, from the surface of which project four
plates (fig. 157), representing apparently the walls of the pollen-sacs,
but destitute of pollen; the chink left between these plates corresponds
thus to the suture of the normal anther.
[Illustration: FIG. 157.--Petaloid stamen of _Viola_, with four
projecting plates.]
The inner or upper portion of the anther-leaf is that which is most
intimately concerned in the formation of pollen; it comparatively rarely
(query ever) happens that the back or lower surface of the antheral leaf
is specially devoted to the formation of pollen. On the other hand, in
cases like those of the common houseleek, where we meet with petaloid
organs combining the attributes of anthers and of carpels, we find the
inner layers devoted to the production of pollen, the outer to the
formation of ovules.
That the pollen-lobes are not to be taken as halves of a staminal leaf,
but rather as specialised portions of it, not necessarily occupying half
its surface, is shown also in the case of double-flowered _Malvaceae_, in
which the stamens are frequently partly petal-like, partly divided into
numerous separate filaments, each bearing a one-, or it may be even a
two-lobed anther. This circumstance is confirmatory of the opinion held
by Payer, Duchartre, Dickson, and other organogenists, as to the
compound nature of the stamens in these plants. The stamens are here
analogues not of a simple entire leaf, but of a lobed, digitate, or
compound leaf, each subdivision bearing its separate anther. On this
subject the reader may consult M. Mueller's paper on the anther of
_Jatropha Pohliana_, _&c._, referred to at page 255.
[310] See C. Morren, "On Spur-shaped Nectarines," &c., 'Ann. Nat.
Hist.,' March, 1841, p. 1. tab. 11.
[311] Karsten, 'Flor. Columb. Spec.,' tab. xxix.
[312] See Dickson, "On Diplostemonous Flowers," 'Trans. Bot. Soc.
Edin.,' vol. viii, p. 100; and on the Androecium of _Mentzelia_,
_&c_., in Seemann's 'Journal of Botany,' vol. iii, p. 209, and vol. iv
(1866) p. 273 (_Potentilla_, _&c._).
[313] See Baillon, 'Adansonia,' iii, p. 351, tab. 12, _Sinapis_.
[314] 'Bull. Acad. Belg.,' xvii, part i, p. 516, c. tab., and
'_Lobelia_,' p. 83.
[315] Cited in 'Bull. Soc. Bot. France,' xiv, p. 253 ('Rev. Bibl.').
[316] 'Bull. Soc. Bot. Fr.,' 1858, p. 331.
[317] 'Mem. Legum.,' p. 44.
[318] 'Bildungsabweich, 'Pflanz. Fam.,' tab. 8, f. 12.
[319] 'Atlas de Goethe' p. 55, t. 4, f. 18.
[320] Wiegmann, 'Bot. Zeit.,' 1831, p. 5, tab. i.
[321] 'Ic. Flor. Germ.,' xiii, tab. 112, cccclxiv, f. 2.
[322] Seemann's 'Journal of Botany,' 1867, p. 317, t. 72, A (_Ophrys_).
[323] 'Enum. Euphorb.' p. 53.
[324] 'Linnaea.' i, p. 457.
[325] 'De Balsam,' p. 17.
[326] B. Clarke, 'Arrangement of Phaenog. Plants,' p. 23.
[327] See 'Engelmann,' p. 26, tab. 3, f. 10, 11, 14.
[328] 'Ann. Sc. Nat.,' ser. 2, t. viii, 1837, p. 58.
[329] 'Bot. Zeit.,' 4, 1846, 889.
[330] 'Verhandl. Nat. Hist. Ver. Preuss. Rheinl. und Westph.,' 1858,
1860, p. 381. Cramer also, 'Bildungsabweich,' p. 90, cites a case in
_Paeonia_ where the carpel was open and petaloid, and bore an anther on
one margin, and four ovules on the other.
[331] 'Euphorbiaceae,' p. 205.
[332] Seemann's 'Journ. Bot.,' iv, p. 168, tab. 47, f. 1.
[333] Moquin-Tandon, l. c., 220, _Passiflora_. Masters, 'Journ. Linn.
Soc.,' 1857, p. 159, _Saponaria_. Seemann's 'Journ. Botany,' vol. iii,
p. 107, _Narcissus_.
[334] 'Bull. Soc. Bot. Fr.,' 1857, p. 452.
[335] 'Gardeners' Chronicle,' 1866, p. 897.
[336] Maout, 'Lecons Element.,' vol. ii, p. 488.
[337] Poiteau and Turpin, 'Arb. Fruit,' t. 37, and Trecul, 'Bull Soc.
Bot. France,' vol. i. p. 307.
[338] Clos, 'Mem. Acad. Toulouse,' 5 ser., vol. iii.
[339] 'Bot. Zeit.,' 1850, t. viii, pp. 514, 664. 'Flora,' (B. Z.) 1832,
t. xv, p. 252; also cited in 'Ann. des Serres et des jardins,' vi, pp.
241-5. See also Schlechtendal, 'Bot. Zeit.,' 1845, t. 3, p. 6.
[340] 'Bull. Soc. Bot. France,' t. viii, p. 453.
[341] See also Allmann, 'Rep. Brit. Assoc.,' July, 1851.
[342] 'Theory of Horticulture,' ed. 2, p. 82.
[343] 'Mem. Soc. Hist. Nat. Paris.' i, 16.
[344] Gen. Munro, 'Trans. Linn. Soc.,' xxvii, p. 7.
[345] 'Bull. Soc. Bot. Fr.,' 1857, p. 21.
[346] 'Ann. Scienc. Nat.,' t. viii, 1837, p. 50, and 'Bot. Zeit.' (R.),
1836, t. xix, p. 513, &c. See also MM. Sourd Dussiples and G. Bergeron,
'Bull. Soc. Bot. France,' viii, p. 349; Von Schmidel, 'Icon. plant. et
Anal. part.' 1782, p. 210, fig. 54.
[347] Godron, 'Bull. Soc. Bot. Fr.,' xiii, p. 82, Rev. Bibl.
[348] Cited in Henfrey, 'Bot. Gazette,' iii, p. 12.
[349] 'Ann. Nat. Hist.,' September, 1856, p. 56. See also Kirschleger,
'Flora (Bot. Zeit.),' xxiv, 1841, p. 340, _Salix alba_. Henschel, 'Flora
(Bot. Zeit.),' 1832, t. xv, p. 253, _S. cinerea_. Hartmann, 'Flora (Bot.
Zeit.),' xxiv, p. 199, _S. nigricans_. Meyer, C. A., 'Bull. Phys.
Math.,' t. x, _S. alba_.
PART IV.
HETEROMORPHY.
There are certain malformations that have little in common beyond this,
that they cannot readily be allocated in either of the great groups
proposed by writers on teratology. There are also deformities which,
unlike the majority of deviations from the ordinary structure, are
absolute and not relative. While the latter are due to an exaggeration,
or to an imperfection of development, or, it may be, to a partial
perversion in organization, the former differ from the normal standard,
not merely in degree, but absolutely. This is often the case when
disease or injury affects the plant; for instance, in the case of galls
arising from insect-puncture the structure is rather a new growth
altogether, than dependent on mere hypertrophy of the original tissues.
These absolute deformities arising from the causes just mentioned belong
rather to pathology than to teratology strictly so called; but, under
the head of deformities, may be mentioned sundry deviations not
elsewhere alluded to.
CHAPTER I.
DEFORMITIES.
The special meaning here attached to the term deformity is sufficiently
explained in the preceding paragraph; it remains to give a few
illustrations, and to refer to other headings, such as Heterotaxy,
Hypertrophy, Atrophy, &c., for malformations capable of more rigid
classification than those here alluded to.
[Illustration: FIG. 166.--Portion of the under surface of a
cabbage-leaf, with horn-like excrescences projecting from it.]
=Formation of tubes.=--The production of ascidia or pitchers from the
cohesion of the margins of one or more leaves has been already alluded
to (see pp. 21, 30), but there is another class of cases in which the
tubular formation is due, not so much to the union of the margins of a
leaf as to the disproportionate growth of some portions as contrasted
with others, whence arises either a depressed cavity, as in the case of
a leaf, or an expanded and excavated structure, when the stem or some
portion of it is affected.
The fruit of the rose, the apple, the fig, and many others, is now
generally admitted to be composed externally of the dilated end of the
flower-stalk in which the true carpels become imbedded. Between such
cases and that of a peltate leaf with a depressed centre, such as often
occurs, to some extent, in _Nelumbium_, there is but little difference.
In cabbages and lettuces there not unfrequently occurs a production of
leaf-like processes projecting from the primary blade at a right angle
(see Enation). Sometimes these are developed in a tubular form, so as to
form a series of little horn-like tubes, or shallow troughs, as in
_Aristolochia sipho_. At other times the nerves or ribs of the leaf
project beyond the blade, and bear at their extremities structures
similar to those just described.
[Illustration: FIG. 167.--Lettuce leaf, bearing on the back a stalked
cup, arising from the dilatation of the stalk (?).]
In a variety of _Codiaeum variegatum_ a similar formation may be seen to
a minor extent. Even the common _Scolopendrium vulgare_ occasionally
produces small pitchers of this character, as in the varieties named
_perafero-corautum_, Moore, and _peraferum_, Woll.[350]
In carnations leaves may sometimes be seen from both surfaces, from
which project long, sharp-pointed tubular spurs at irregular intervals.
A very singular illustration of this is figured by Trattinick,[351], in
which the leaves, epicalyx, sepals, and petals, were all provided with
tubular spurs.
In _Cephalotus follicularis_ rudimentary or imperfect pitchers may be
frequently met with, in which the stalk of the leaf is tubular and bears
at its extremity a very small rudimentary leaf-blade. It is not in all
cases easy to trace the origin and true nature of the ascidium, as the
venation is sometimes obscure. If there be a single well-marked midrib
the probability is that the case is one of cohesion of the margins of
the leaf; but if the veins are all of about equal size, and radiate from
a common stalk, the pouch-like formation is probably due to dilatation
and hollowing of the petiole. Again, when the result of a union of the
margins of the leaf, the pitcher is generally less regular than when
formed from the hollowed end of a leaf-stalk. Further information is
especially needed as to the mode of development and formation of these
tubular organs, so as to ascertain clearly when they are the result of a
true cupping process, and when of cohesion of the margins of one or more
leaves. (See Cohesion, p. 31. For bibliographical references consult
also A. Braun, 'Flora v. Bot. Zeit.,' 1835, t. xviii, p. 41,
_Aristolochia_.)
=Tubular formations in the flower.=--A similar formation of tubes
happens in some double flowers; for instance, it is not infrequent in
double flowers of _Primula sinensis_, in which tubular petal-like
structures are attached to the inner surface of the corolla; sometimes
these petaloid tubes replace the stamens, while at other times they
appear to have no relation to those organs. In the particular flowers
now alluded to the tubular form seems due to a dilatation, and not to a
cohesion of the margins. (See Cohesion, p. 23.) These tubular petals
resemble in form and colour almost precisely the normal corolla in
miniature, but are not surrounded by a calyx, nor do they contain
stamens, while the less perfect forms show clearly their origin from a
single tube-like organ.
[Illustration: FIG. 168.--Corolla of _Primula sinensis_ turned back to
show a tubular petal springing from it. One only is shown for the sake
of clearness; they are generally numerous.]
The formation of spurs or spur-like tubes in a quasi-regular manner has
been spoken of under the head of Irregular Peloria, p. 228, but we
occasionally meet with tubular processes which seem to occur in an
irregular manner, and to have no reference to the symmetrical plan of
the flower, and which are due probably to the same causes as those which
induce hypertrophy. Such spurs have frequently been seen on the corolla
of _Digitalis purpurea_, _Antirrhinum majus_,[352] _Tulipa Gesneriana_,
and occasionally on the sepals of _Fuchsia_. They are very frequent in
some seasons in the corolla of certain calceolarias (_C. floribunda_).
By Morren this production of adventitious spurs was called
"Ceratomanie."
[Illustration: FIG. 169.--Corolla of _Calceolaria_, showing irregular
tubular spurs projecting from the lower lip.]
Similar processes may sometimes be seen in the capsules of _Linaria
vulgaris_, as also in the fruits of some of the Solanums, quite without
reference to the arrangement of the carpels, so that their production
seems to be purely irregular.
Morren, as previously remarked, gave the name "Solenaidie" to tubular
deformities affecting the stamens, a term which has not been generally
adopted; the deformity in question is by no means of uncommon occurrence
in some double or partially pelorised flowers, as _Antirrhinum_,
_Linaria_, &c. A similar formation of conical out-growths may frequently
be met with in the fruits quite irrespectively of any disjunction of the
carpels.
=Contortion.=--An irregular twisting or bending of the stem or branches
is by no means of uncommon occurrence, the inducing causes being often
some restriction to growth in certain directions, or the undue or
disproportionate growth in one direction, as contrasted with that in
another. Hence it may arise from insect-puncture, parasitic growth, or
any obstacle to the natural development. Frequently it exists in
conjunction with fasciation, the ends of the branches being curved round
like a shepherd's crook, from the growth on one side being so much
greater than on the other. Sometimes it is a mere exaggeration of a
normal condition; thus, in what are termed flexuose stems the stem
twists alternately to one side or another, frequently in association
with an oblique form of 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 serving to restrain the growth.
A similar irregularity of growth occurs, not unfrequently, in the case
of crocus leaves, when in the course of their growth, as they push their
way through the soil, their progress becomes checked either by a stone
or even by frost.
=Spiral torsion.=--Growth in a spiral direction, and the arrangement of
the various organs of the plant in a spiral manner, are among the most
common of natural phenomena in plants.[356] Fibres are coiled spirally
in the minute vessels of flowering plants, and are not wholly wanting
even among fungi. The leaf-organs are very generally spirally arranged;
the leaf-stalks are often so twisted as to bring leaves on one plane
which otherwise would occupy several. In the leaf itself we have a
spiral twist taking place constantly in _Alstroemeria_, in _Avena_, and
other plants. A similar tendency is manifested in the flower-stalks, as
in _Cyclamen_ and _Vallisneria_, and the whole inflorescence, as in
_Spiranthes_. Even the bark and wood of trees is often disposed
spirally. This is very noticeable in some firs, and in the bark of the
sweet chestnut (_Castanea_), of _Thuja occidentalis_, and other trees.
The knaurs or excrescences which are sometimes found on the roots or
stems of trees afford other illustrations of this universal tendency.
These bodies consist of a number of embryo buds, which, from some cause
or other, are incapable of lengthening. On examination every rudimentary
or undeveloped bud may be seen to be surrounded by densely crowded
fibres arranged spirally.
The axes of nearly all twining plants are themselves twisted, and
twisted in a direction corresponding to the spontaneous revolving
movement exhibited by these plants, as in the hop, the convolvulus,
passion flower, &c., the degree of twisting being dependent to a great
extent on the roughness of the surface around which the stem
twines[357].
Considered as an exceptional occurrence, it occurs frequently in certain
plants, and, when it affects the stem or branches, necessarily causes
some changes in the arrangement of the parts attached to them; thus,
spiral torsion of the axial organs is generally accompanied by
displacement of the leaves, whorled leaves becoming alternate, and
opposite or whorled leaves becoming arranged on one side of the stem
only. Frequently also this condition is associated with fasciation, or,
at least, with a distended or dilated state. An illustration of this in
_Asparagus_ has been figured at p. 14.
Very often the leaves are produced in a spiral line round the stem, as
in a specimen of _Dracocephalum speciosum_ described and figured by C.
Morren. The leaves of this plant are naturally rectiserial and
decussate, but, in the twisted stem the leaves were curviserial, and
arranged according to the 5/13 plan. Now, referring to the ordinary
notation of alternate leaves, we shall have the first leaf covered by
the fifth, with two turns of the spiral; since decussate leaves result
from two conjugate lines, the formula will be necessarily 2/5. The
fraction 5/13 hence comes regularly into the 2/5 series (2/5, 3/8,
5/13). Thus, the leaves in assuming a new phyllotaxy, take one quite
analogous to the normal one.
One of the most curious instances that have fallen under the writer's
own observation occurred in the stem of _Dipsacus fullonum_. (See
'Proceedings of the Linnean Society,' March 6, 1855, vol. ii, p. 370).
The stem was distended, and hollow, and twisted on itself; its fibres,
moreover, were arranged in an oblique or spiral direction; the branches
or leaf-stalks, which usually are arranged in an opposite and decussate
manner, were, in this case, disposed in a linear series, one over the
other, following the line of curvature of the stem. When the course of
the fibres was traced from the base of one of the stalks, upward around
the stem, a spiral was found to be completed at the base of the second
stalk, above that which was made the starting point. Now, if opposite
leaves depend on the shortened condition of the internode between the
two leaves, then, in the teazel-stem just described, each turn of the
spiral would represent a lengthened internode; and, if the fibres of
this specimen could be untwisted, and made to assume the vertical
direction, and, at the same time, the internodes were shortened, the
result would be the opposition of the branches and the decussation of
the pairs; this explanation is borne out by the similar twisting which
takes place so frequently in the species of _Galium_ and other
_Rubiaceae_.
[Illustration: FIG. 172.--Twisted stem of _Dipsacus fullonum_.]
G. Franc[358] was one of the first to notice this twisting in _Galium_,
and M. Duchartre,[359] in mentioning a similar instance, gives the
following explanation of the appearance which will be found to apply to
most of these cases. In the normal stem of _Galium Mollugo_ the
branches are opposite in each verticil and crossed in the two
successive ones. The stem is four-angled, each angle having a nerve.
Each of these nerves, springing from the origin of a branch in one
whorl, terminates in the interval which separates the point of origin of
the two branches in the whorl next above it. In the deformed stem one of
the nerves corresponds to the insertion of a branch, its neighbour is in
the adjoining vacant space; hence it results that four nerves correspond
to two branches and to two consecutive interspaces, and hence the
analogy between a single normal internode provided with its two branches
and its four nerves. What confirms this inference is that the nerve,
which begins at the point of origin of a branch, after making one spiral
turn round the stem, terminates in the interval that separates the two
following branches, just as in a branch of the normal stem it ends in
the upper whorl between the two next branches. The torsion, then, in
this _Galium_ caused the separation of the two opposite branches of the
same verticil, and placed them one above another, and this being
reproduced in all the whorls, all the branches come to be arranged on
the same longitudinal line. The leaves are susceptible of the same
explanation; they are inserted in groups of three or four in one arc
round the origin of each branch. In the malformation each series or
group of four leaves, with its central branch, is equivalent to half a
whorl of the natural plant with its axillary branch. In other words, the
malformation consists in a torsion of the stem, which separates each
whorl into two distinct halves; these half-whorls, with their axillary
branches, are placed on a single longitudinal series one above another.
This case is quoted at some length, as it is an admirable example of a
very common form of malformation in these plants.
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.)
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 _Alstroemeria_ 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 _Codiaeum 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]
=Adventitious tendrils.=--Under ordinary circumstances tendrils may be
described as modifications of the leaf, the stipule, the branch, or of
the flower stalk, so that it is not a matter of surprise to find
tendrils occasionally springing from the sepals or petals, as indeed
happens normally in _Hodgsonia_, _Strophanthus_, _&c._
M. Decaisne[363] found a flower of the melon in which one of the
segments of the calyx was prolonged into a tendril, and Kirschleger
records a similar instance in the cucumber, while Mr. Holland ('Science
Gossip,' 1865, p. 105) mentions a case in which one of the prickles on
the fruit of a cucumber had grown out into a tendril.
In _Cobaea scandens_ the foliar nature of the tendril is shown by the
occasional presence of a small leaflet on one of the branches of the
tendril, and a similar appearance may frequently be seen in
_Eccremocarpus scaber_. On the other hand, in the vine, the axial nature
of the tendril is revealed by the not infrequent presence of flowers or
berries on them, as also in _Modecca_ and some _Passifloraceae_.
Darwin, speaking of the tendrils of _Bignonia capreolata_, says it is a
highly remarkable fact that a leaf should be metamorphosed into a
branched organ, which turns from the light, and which can, by its
extremities, either crawl like a root into crevices, or seize hold of
minute projecting points, these extremities subsequently forming
cellular masses, which envelope by their growth the first fibres and
secrete an adhesive cement.
=Interrupted growth.=--This term is here used in the same sense as in
ordinary descriptive botany, as when an "interruptedly pinnate" leaf is
spoken of. A similar alternation may be observed occasionally as a
teratological occurrence, though it is not easy to account for it.
[Illustration: FIG. 175.--Interrupted growth of Radish (from the
'American Agriculturist.')]
[Illustration: FIG. 176.--Interrupted growth in Apple.]
Fig. 175 shows an instance of the kind in a radish, and fig. 176 a
similar deformity in the case of an apple, the dilatation of the
flower-stalk below the ordinary fruit producing an appearance as if
there were two fruits one above another.
In leaves this peculiar irregularity of development is more common.
In some varieties of _Codiaeum variegatum_ the leaves resemble those of
_Nepenthes_, as the basal portion is broad, and terminates in a
projecting midrib destitute of cellular covering, and this again
terminates in a small pouch or pitcher. Somewhat similar variations may
be found in ferns, especially _Scolopendrium vulgare_.
Instead of the pouch there is formed sometimes in the plant last
mentioned a supplementary four-lobed lamina, the four lobes being in two
different planes, and diverging from the midrib, so that the section
would resemble [Symbol: Sideways X], the point of intersection of the x
representing the position of the midrib. This four-winged lamina is thus
very similar to the four-winged filaments described and figured at p.
289, and to the leaf-like anther of _Jatropha_ described by M. Mueller,
p. 255.
=Cornute leaves= (_Folia cornuta_).--The condition to which this term
applies is that in which the midrib, after running for a certain
distance, generally nearly to the point of the leaf, suddenly projects,
often in a plane different from that of the leaf, and thus forms a small
spine-like out-growth. Should this happen to be terminated by a second
laminar portion, an interrupted leaf would be formed. In _Scolopendrium
vulgare_ and other ferns this condition has been noticed, as also in
some of the varieties of _Codiaeum variegatum_ already referred to.
=Flattening.=--There are some plants whose stem or branches, instead of
assuming the ordinary cylindrical form, are compressed or flattened;
such are some species of _Epiphyllum_, _Coccoloba_, _Bauhinia_, &c. The
same thing occurs in the leaf-like branches of _Ruscus_, the
flower-stalks of _Xylophylla_, _Phyllanthus_, _Pterisanthes_. Martins
proposes to apply the word 'cladodium' to such expansions, just as the
term phyllodium is applied to the similar dilatation of the leaf-stalks.
If we exclude instances of fasciation, _i.e._ where several branches
are fused together and flattened, we must admit that this flattening
does not occur very often as a teratological appearance.
Mr. Rennie figures and describes a root of a tree which had become
greatly flattened in its passage between the stones at the bottom of a
stream, and had become, as it were, moulded to the stones with which it
came into contact.[364]
The spadix of _Arum_, as also of the cocoa-nut palm, has been observed
flattened out, apparently without increase in the number of organs.
When the blade of the leaf is suppressed it often happens that the stalk
of the leaf is flattened, as it were, by compensation, and the petiole
has then much the appearance of a flat ribbon (phyllode). This happens
constantly in certain species of _Acacia_, _Oxalis_, &c., and has been
attributed, but doubtless erroneously, to the fusion of the leaflets in
an early state of development and in the position of rest.[365]
In some water plants, as _Sagittaria_, _Alisma_, _Potamogeton_, &c., the
leaf-stalks are apt to get flattened out into ribbon-like bodies; and
Olivier has figured and described a _Cyclamen_, called by him _C.
linearifolium_, in which, owing to the suppression of the lamina, the
petiole had become dilated into a ribbon-like expansion--deformation
rubanee of Moquin.
FOOTNOTES:
[350] Moore, 'Nature Printed Ferns,' 8vo edition, vol. ii, p. 154, et p.
173.
[351] 'Flora (B. Z.),' 1821, vol. iv, p. 717, c. tab.
[352] Chavannes, 'Mon. Antirrh.'
[353] 'Bull. Soc. Bot. France,' t. vii, 1860, p. 877.
[354] Ibid., t. iv, 1857, p. 759.
[355] Jaeger, "De monstrosa folii _Phoenicis dactyliferae_
conformatione a Goetheo olim observata," 'Act. Acad. Leop. Car. Nat.
Cur.,' vol. xvii, suppl., p. 293, c. tab. color. iv.
[356] See Goethe, 'Ueber die spiral Tendenz.'
[357] See Darwin "On Climbing Plants," 'Journ. Linn. Soc. Botany,' vol.
ix, p. 5.
[358] 'Ephem. Nat. Cur.,' dec. 2, ann. 1, 1683, p. 68, fig. 14.
[359] 'Ann. des Scienc. Nat.,' third series, vol. i, 1844, p. 292.
[360] 'Flora' Feb. 4, 1858, p. 69, tab. ii, f. 3, and also 'Flora,'
1860, p. 737, tab. vii, f. 9.
[361] 'Bull. Acad, Belg.,' t. xvii, p. 196, "Lobelia," p. 53, c. tab.
[362] Moore, 'Nature-printed Ferns,' 8vo edition, vol. ii, p. 183.
[363] 'Bull. Soc. Bot. Fr.,' 1860, vol. vii, p. 461. See also Naudin,
'Ann. Sc. Nat.,' 4 ser., t. iv, p. 5. Clos, 'Bull. Soc. Bot. Fr.,' t.
iii, p. 546.
[364] London's 'Magazine Nat. Hist.,' vol. ii, p. 463.
[365] C. Morren, 'Bull. Acad. Belg.,' 1852, t. xix, part iii, p. 444.
CHAPTER II.
POLYMORPHY.
Usually the several organs of the same individual plant do not differ to
any great extent one from another. One adult leaf has nearly the same
appearance and dimensions as another; one flower resembles very closely
another flower of the same age and so on. Nevertheless it occasionally
happens that there is a very considerable difference in form in the same
organs, not only at different times, but it may also be at the same
time. Descriptive botanists recognise this occurrence in the case of
leaves, and apply the epithet heterophyllous to plants possessed of
these variable foliar characters. In the case of the flower, where
similar diversity of form occasionally exists, the term dimorphism is
used.
As these phenomena appear constantly in particular plants, they are
hardly to be looked on, under such circumstances, as abnormal, but where
they occur in plants not usually polymorphic, they may be considered as
coming within the scope of teratology.
=Heterophylly.=--As a general rule, the leaves or leaf-organs in each
portion of a plant, from the rhizome or underground axis, where it
exists, to the carpellary leaf, have their own special configuration,
subject only to slight variations, dependent upon age, conditions of
growth, &c. The cotyledons are very uniform in shape in each plant, and
are scarcely ever subject to variation. The leaves near the base of the
stem, the root-leaves as they are not unfrequently called, sometimes
differ in form from the stem-leaves; these again differ from the bracts
or leaves in proximity to the flower. The floral envelopes themselves,
as well as the bud-scales, all have their own allotted form in
particular plants, a form by which they may, in most cases, be readily
recognised. Hence, then, in the majority of plants there is naturally
very considerable difference in the form of the leaf-organs, according
to the place they occupy and the functions they have to fulfil; but, in
addition to this, it not unfrequently happens that the leaf-organs in
the same portion of the stem are subject to great variation in form.
This is the condition to which the term heterophylly properly applies.
The variation in form is usually dependent on a greater or less degree
of lobing of the margin of the leaf; thus, in the yellow jasmine, almost
every intermediate stage may be traced from an ovate entire leaf to one
very deeply and irregularly stalked. _Broussonettia papyrifera_, and
_Laurus Sassafras_, and the species of _Panax_, may be mentioned as
presenting this condition. Sometimes in the last-named genus, as also in
_Pteridophyllum_, every gradation between simple and compound leaves may
be traced. The horse-radish (_Cochlearia Armoracia_) may also be
instanced as a common illustration of polymorphism in the leaves. In
ferns it is likewise of frequent occurrence, markedly so in
_Scolopendrium D'Urvillei_, in which plant every gradation from a simple
oblong frond to an exceedingly divided one may be found springing from
the same rhizome at the same time.
[Illustration: FIG. 177.--_Syringa persica laciniata_, showing
polymorphous leaves.]
A similar protean state, but little less remarkable, occurs in many of
our British ferns, notably in _Scolopendrium vulgare_, of which Mr.
Moore enumerates no fewer than 155 varieties,[366] many of the forms
occurring on the same plant at the same time. Cultivators have availed
themselves of this tendency to produce multiform foliage, not only for
the purposes of decoration or curiosity, as in the many cut-leaved or
crisped-leaved varieties, but also for more material uses, as, for
instance, the many varieties of cabbages, of lettuces, &c. Most of these
variations are mentioned under the head of the particular morphological
change of which they are illustrations.
The effect of a change in the conditions of growth in producing
diversity in the form of the leaf may be here alluded to. _Ficus
stipulata_, a plant used to cover the walls of plant-stoves in this
country, and growing naturally on walls in India, like ivy, produces
leaves of very different form, size, and texture, when grown as a
standard, from what it does when adhering to a wall. _Marcgraavia
umbellata_ furnishes another example of a similar nature, as indeed, to
a less extent, does the common ivy.
Allusion has been already made to the occasional persistence of forms in
adult life, which are commonly confined to a young state, as in the case
of some conifers which present on the same plant, at the same time, two
different forms of leaves. Mention has also been made of the presence of
adventitious buds on leaves and in other situations. The leaves that
spring from these buds are usually of the same form as the other leaves
of the plant, but now and then they differ. Of this a remarkable
illustration is afforded by a fern, _Pteris quadriaurita_, in which the
fronds emerging from an adventitious bud are very different from the
ordinary fronds.
[Illustration: FIG. 178.--Portion of a frond of _Pteris quadriaurita_,
with an adventitious bud, the form of the constituent foliage of which
is very different from that of the parent frond.]
=Dimorphism.=--This term, applied specially to the varied form which the
flowers or some of their constituent elements assume on the same plant,
is an analogous phenomenon to what has been above spoken of as
heterophylly, and, like it, it cannot, except under special
circumstances, be considered as of teratological importance. A few
illustrative cases, however, may here be cited.
Sir George Mackenzie describes a variety of the potato[367] (_Solanum
tuberosum_), which produces first double and sterile flowers, and
subsequently single fertile ones; the other portions of the plant do not
differ much.
_Stackhousia juncea_, according to Clarke, has mixed with its perfect
flowers a number of apetalous blossoms destitute of anthers.[368]
This peculiarity is well exemplified in the tribe _Gaudichaudieae_ of the
order _Malpighiaceae_. A. de Jussieu, in his monograph, speaks of these
flowers as being very small, green, destitute of petals, or nearly so,
with a single, generally imperfect anther; the carpels also are more or
less imperfect, but not sufficiently so to prevent some seeds from being
formed. A similar production of imperfect flowers has been noticed in
many other orders, _e.g._ _Violaceae_, _Campanulaceae_, &c. In some cases
these supplementary blossoms are more fertile and prolific in good seeds
than are the normally constructed flowers. M. Durieu de Maisonneuve
alludes to a case where flowers of this description are produced below
the surface of the ground. The plant in question is _Scrophularia
arguta_, and it appears that towards the end of the summer the lowest
branches springing from the stem bend downwards, and penetrate the soil;
the branches immediately above the lowest ones also bend downwards, but
do not always enter the earth. These branches bear fertile flowers:
those which are completely below the soil are completely destitute of
petals; those which are on the surface have a four-lobed corolla whose
divisions are nearly equal, like those of _Veronica_.[369]
To Sprengel, and specially to Darwin, physiologists are indebted for the
demonstration of the relation of di- and trimorphic flowers to
fertilisation. In certain genera of orchids, such as _Catasetum_, &c.,
flowers of such different form are produced that botanists, without
hesitation, considered them as belonging to different genera, until the
fact of their occasional production on the same plant showed that they
were not of even specific importance. It was reserved for Mr. Darwin to
show experimentally that these very different flowers are really sexual
forms of one and the same species, ordinarily occurring on different
plants, i.e. dioecious, but occasionally formed on the same spike. The
same excellent observer has demonstrated that the di- and trimorphic
forms of _Primula_, of _Linum_, _Lythrum_, and other plants--forms
differing mainly in the relative length of the stamens and styles, are
also connected with striking differences in the number of perfect seeds
produced. The most perfect degree of fertility is obtained when the
stigma of one form is fertilised by the pollen taken from stamens of a
corresponding height. On the other hand, when the union is, as Mr.
Darwin states, illegitimate, that is, when the pollen is taken from
stamens not corresponding in length to the style, more or less complete
sterility ensues in the progeny, sometimes even utter infertility, such
as happens when two distinct species are crossed, so that, in point of
fact, the offspring of these illegitimate unions correspond almost
precisely to hybrids.[370]
Mere variations of form arising from hybridisation or other causes
hardly fall within the limits of this work, though it is quite
impossible to say where variations end and malformations begin. There
are, however, two or three cases cited by Mr. Darwin[371] from Gallesio
and Risso to which it is desirable to allude. Gallesio impregnated an
orange with pollen from a lemon, and the fruit borne on the mother tree
had a raised stripe of peel like that of a lemon both in colour and
taste, but the pulp was like that of an orange, and included only
imperfect seeds. Risso describes a variety of the common orange which
produces "rounded-oval leaves, spotted with yellow, borne on petioles,
with heart-shaped wings; when these leaves fall off they are succeeded
by longer and narrower leaves, with undulated margins, of a pale green
colour, embroidered with yellow, borne on foot-stalks without wings.
The fruit whilst young is pear-shaped, yellow, longitudinally striated
and sweet; but, as it ripens, it becomes spherical, of a reddish-yellow,
and bitter."
=Sports or bud variations.=--These curious departures from the normal
form can only be mentioned incidentally in this place, as they pertain
more to variation than to malformation.
The occasional production of shoots bearing leaves, flowers, or fruits
of a different character from those found on the normal plant, is a fact
of which gardeners have largely availed themselves in the cultivation of
new varieties. The productions in question have been attributed to
various causes, such as cross-breeding, grafting, budding, dissociation
of hybrid characters, or reversion to some ancestral form, all of which
explanations may be true in certain cases, but none of them supply the
clue to the reason why one particular branch should be so affected, and
the rest not; or why the same plant, at the same time, as often happens
in Pelargoniums, should produce two, three, or more "sports" of a
different character.
These bud variations may be perpetuated by grafts or by cuttings,
sometimes even by seed. With reference to cuttings a curious
circumstance has been observed, viz., that if taken from the lower part
of the stem, near the root, the peculiarity is not transmitted, but the
young plant reverts to the characters of the typical form (Carriere).
This circumstance, however, is not of universal occurrence.
For further particulars on this interesting subject the reader is
referred to Darwin's 'Variation of Animals and Plants,' i, p. 373, where
numerous references are given, and wherein certain well-known and highly
remarkable instances, such as the _Cytisus Adami_, the trifacial orange,
&c., are discussed.
FOOTNOTES:
[366] 'Nature-printed Ferns,' 8vo edition, vol. ii, p. 197.
[367] 'Gard. Chron.,' 1845. p. 790.
[368] 'A New Arrangement of Phaenog. Plants,' p. 36.
[369] 'Bull. Soc. Bot. France,' 1856, t. iii, p. 569.
[370] The reader will find an abstract of Mr. Darwin's views in his work
on the 'Variation of Animals and Plants,' vol. ii, p. 181.
[371] Loc. cit., i, 336.
CHAPTER III.
ALTERATIONS OF COLOUR.[372]
Changes in the colour of the several organs of plants are more often
either pathological or the result of variation than of malformation
properly so called.
Alterations in colour arise from a diminished or an increased amount of
colouring matter, or from an unusual distribution of the solid or fluid
matters on which the colour depends. The superposition of cells
containing colouring material of different tints produces naturally a
very different set of hues from those which are manifested when the
colours are not blended. Referring the reader to the ordinary text-books
on vegetable physiology and chemistry for details as to the nature and
disposition of colouring materials in plants under natural
circumstances, it will only be necessary to cite a few instances of
deviation from the general colour of plants or their organs.
=Albinism.=--This change is due to the deficient formation of green
colouring matter or chlorophyll, and is more a pathological condition
than a deformity.
It seems necessary to draw a distinction between this state and ordinary
blanching or etiolation. In the former case chlorophyll seems never to
be formed in the affected parts, even if they be exposed to light, while
an etiolated organ, when placed under favorable circumstances, speedily
assumes a green colour. In _Richardia aethiopica_ one or more leaves
become occasionally as white as the spathe is usually.
=Virescence.=--Engelmann[373] pointed out that, so far as flowers were
concerned, there are two ways in which they assume a green colour,
either by a simple development of chlorophyll in place of the colouring
matter proper to the flower, or by an actual development of leaf-like
organs in the room of the petals--frondescence. Morren[374] judiciously
proposed to keep these two conditions separate, calling the one
virescence, the other frondescence (see p. 241).
Many of the cases recorded as reversions of the parts of the flower to
leaves are simply instances of virescence; indeed, it is not in all
cases easy to distinguish between the two states. The examination of the
arrangement of the veins is often of assistance in determining this
point; for instance, if, under ordinary circumstances, the venation of
the petal be such as is characteristic of the sheath of the leaf, while
in the green-coloured flower of the same species the venation is more
like that which belongs to the blade of the leaf, the inference would,
of course, be that the green colour was due to frondescence or phyllody.
The persistence or duration of petals is often increased when they are
subject to this change; instead of falling off speedily they become
persistent when so affected.
Some flowers are more liable to virescence than others. The common
honeysuckle, _Lonicera Periclymenum_, is one of these, and it is
noticeable in this plant that the calyx remains unaffected--a
circumstance which Morren says shows the distinctness of virescence from
frondescence; for, in this instance, we have the most foliaceous portion
of the flower remaining unchanged, while the corolla and other organs,
usually less leaf-like in their nature, assume a green colour; but this
may rather be attributed to the axial nature of the so-called adherent
calyx. The stamens in these green-flowered honeysuckles are usually
green also, but with abortive anthers, and the pistil also is in a
rudimentary condition. _Umbelliferae_ are not unfrequently subject to
this change, _e.g._, _Torilis Anthriscus_, _Daucus Carota_, _Heracleum
Sphondylium_, _Carum carui_, &c. _Primulaceae_, again, are frequently
subject to virescence. Among _Compositae_ the following species are
recorded as having had green flowers--_Cirsium tricephalodes_, _Senecio
vulgaris_, _Calendula officinalis_, _Pyrethrum Parthenium_, _Carduus
crispus_, _Hypochaeris radicata_, _Hieracium prealtum_, _Cirsium
arvense_, _Coreopsis Drummondi_.[375] In _Ranunculaceae_ virescence has
been observed in _Delphinium elatum_, _crassicaule_ and _Ajacis_,
_Anemone hortensis_ and _nemorosa_, _Aquilegia vulgaris_, _Ranunculus
Philonotis_.
Many of these cases, and others that might be cited, are probably
instances of frondescence or phyllody (see p. 241).
=Chromatism.=--This term is here intended to apply specially to those
cases in which any organ of a plant assumes a colour approximating to
that of the petals, or in which the normal green is replaced by tints of
some other colour. To a certain extent the change in question is the
same as that spoken of under the head of petalody (see p. 283), but
there are cases in which, while the ordinary situation and form are
those of leaves, the coloration is that of the petals. Such was the case
in the _Gesnera_ mentioned by Morren (see p. 88), and in which a leaf
occupied the position of an inflorescence, and became brightly coloured.
In tulips the presence of a highly coloured leaf on the flower-stalk,
below the flower, is not uncommon. So also the bracts or leaves below
the perianth in _Anemone coronaria_ and _hortensis_ not unfrequently
assume the coloration usually confined to the parts of the perianth. A
similar illustration has presented itself, as this sheet is passing
through the press, in which two of the leaflets of the compound leaf of
a rose were brightly coloured like the petals, the others being of
their ordinary green colour.
The occurrence of coloured bracts, as in _Poinsettia_, _Bougainvillea_,
&c., is very common under natural conditions, and need not here be
further alluded to.
Increased intensity of colour often accompanies teratological changes;
an instance has just been alluded to in the _Gesnera_; the feather
hyacinth, _Muscari comosum_, furnishes another illustration, the
adventitious pedicels being brightly coloured.
In fasciated stems, also, of herbaceous plants, it not unfrequently
happens that the upper portions of the stem are brightly coloured.
The occurrence of flowers or fruits of different colours on the same
plant, or even in the same cluster, is a phenomenon which does not come
within the scope of the present book; the reader may, however, be
referred to the excellent summary on this subject published by Mr.
Darwin in his work on the 'Variation of Animals and Plants under
Domestication.'
FOOTNOTES:
[372] These deviations are treated of under the head of alterations of
form, because they are not, in a teratological point of view, of
sufficient importance to demand a specific heading, while they appeal to
the sight in the same way as the deviations from the customary forms of
organs.
[373] 'De Antholys,' p. 32, Sec. 38.
[374] 'Bull. Acad. Belg.,' xvii, part 2, p. 131, c. tab.
[375] See Cramer, 'Bildungsabweich,' pp. 17, 55, 82, 65. See also Lucas,
'Verhandl. des Bot. Vereins. Brandenb.,' heft 1, 2, _Anchusa_. Christ,
'Flora,' 1867. pp. 376, tab. 5, 6, _Stachys_.
BOOK III.
DEVIATIONS FROM THE ORDINARY NUMBER OF ORGANS.
To a certain extent the number of the organs of a plant is of even
greater consequence for purposes of classification than either their
form or their arrangement; for instance, the number of cotyledons in the
embryo is made the chief basis of separation between the two great
groups of flowering plants, the monocotyledons and the dicotyledons. In
the one group, moreover, the parts of the flower are arranged in groups
or whorls of five; in the other the arrangement is ternary. In mosses
the teeth of the peristome are arranged in fours, or in some multiple of
that number. So far as the larger groups are concerned, and also in
cases where the actual number of parts is small, the numerical relations
above described are very constant; on the other hand, in the minor
subdivisions, and especially where the absolute number of parts is
large, considerable variation may occur, so that descriptive botanists
frequently make use of the term indefinite, and apply it to cases where
the number of parts is large and variable, or, at any rate, not easy to
be estimated.
Considered teratologically, the changes, as regards the number of
organs, are readily grouped into those consequent on a decreased and
into those resulting from an increased development. The alteration may
be absolute or relative. There may be an actual deficiency in the number
of parts or an increase in their number, but in either case the change
may be simply a restoration of the primitive number, a species of
peloria, in fact. An increased number of parts, moreover, may depend not
so much on the formation of additional parts as on the subdivision of
one.
It seems also desirable to treat separately those cases in which there
is an increased number of buds either leaf-buds or flower-buds, as the
case may be, as happens in what is termed prolification. This formation
of buds occurring, as it does, often in unwonted situations is treated
of under the head of alterations of arrangement, the mere increase in
number being considered of subordinate importance as contrasted with the
altered disposition (see p. 100).
PART I.
INCREASED NUMBER OF ORGANS.
An augmentation in the number of parts may arise from several causes,
and may sometimes be more apparent than real. True multiplication exists
simply as a result of over-development; the affected organs are repeated
sometimes over and over again each in their proper relative position,
and without any transmutation of form.
Metamorphy, on the other hand, often gives rise to the impression that
parts are increased in number, when it may be that the stamens and
pistils, one or both, are not so much increased in number as altered in
appearance. The double anemones and ranunculus of gardens, amongst many
other analogous illustrations, may be mentioned. In these flowers, owing
to the petalody of the stamens and pistils, one or both, an impression
of exaggerated number is produced, which is by no means necessarily a
true one. Fission or lateral subdivision also gives rise to an apparent
increase in number; thus, some so-called double flowers, the elements of
which appeared to be increased in numbers, owe the appearance merely to
the laciniation or subdivision of their petals.
The French botanists, following Dunal and Moquin, attribute an increase
in the number of whorls in the corolla, and other parts of the flower,
to a process which they call chorisis, and they consider the
augmentation to be due to the splitting of one petal, for instance, into
several;--somewhat in the same manner as one may separate successive
layers of talc one from the other.
English botanists, on the other hand, have been slow to admit any such
process, because, in most instances, no alteration in the law of
alternation takes place in these double flowers, and in those few cases
where the law is apparently infringed, the deviation is explained by the
probable suppression of parts, which were they present would restore the
natural arrangement of the flower; and, that this is no imaginary or
purely theoretical explanation, is shown by some of the _Primulaceae_,
wherein a second row of stamens is occasionally present in the adult
condition, and renders the floral symmetry perfect.
The double daffodil, where there are from forty to fifty petaloid organs
instead of fifteen, and wherein each piece exhibits a more or less
perfect coronal lobe at the junction of the claw and the limb, has been
cited as an objection to chorisis, though it is difficult to see on what
grounds.
In _Delphinium_, as shown by Braun,[376] the stamens and carpels are
members of a continuous spiral series, and in the double balsam an extra
corolline whorl is produced, without the suppression of the stamens, in
the following manner: the ordinary stamens are replaced by petals, the
carpels by stamens, while an additional whorl of carpels is produced at
the summit of the axis. In this instance, therefore, the doubling is
distinctly referrible to an absolute increase in the number of whorls,
and not to chorisis.[377]
On the other hand, it must be admitted that there are many cases which
are not to be explained in any other way than that suggested by the
French botanists before alluded to. Probably, the main difficulty in the
way of accepting the doctrine of chorisis is the unfortunate selection
of the word used to designate the process; this naturally suggests a
splitting of an organ already perfectly formed into two or more
portions, either in the same plane as the original organs, "parallel
chorisis;" or at right angles to it "collateral chorisis." Indeed,
before so much attention had been paid to the way in which the floral
organs are developed, it was thought that an actual splitting and
dilamination did really take place; Dunal and Moquin both assert as
much. The truth would rather seem to be that, in the so-called parallel
chorisis at least, the process is one of hypertrophy and
over-development rather than of splitting. The adventitious petal or
scale is an excrescence or an outgrowth from the primary organ, and
formed subsequently to it.
In the case of "compound stamens" the original stamens are first
developed each from its own cellular "mamelon," or growing point; and,
after a time, other secondary growing points emerge from the primary
one, and in this way the stamens are increased in number, without
reference, necessarily, to the so-called law of alternation. Outgrowths
from leaves, multiplying the laminar surface, are alluded to under the
head of hypertrophy, and it is probable that some of the cases of
duplication of the flower, or of the formation of adventitious segments
outside the ordinary corolla as alluded to in succeeding paragraphs (see
Pleiotaxy of the corolla), are due to a similar process.[378]
The formation of parts in unwonted numbers may be merely a reversion to
what is supposed to have been the original form, and in this way there
may be a restoration of parts that are usually undeveloped or
suppressed. There can be little or no doubt that there are in reality
six stamens in _Orchidaceae_, of which one only, under ordinary
circumstances, is developed. When the numerical symmetry is restored, as
it sometimes is, it is obvious that the augmentation that occurs is of a
different character from that arising from a repetition or renewed
development of organs. When the increased number arises from
multiplication proper, or from repetition, the ordinary laws of
alternation are not interfered with, but if from chorisis or
"dedoublement," it may happen that the normal arrangement is disturbed.
Without studying the mode of development, it is not in all cases
possible to tell under which of the above categories any particular
instance should be placed; hence, in the following sections, except
where otherwise stated, the cases are grouped according to the
appearance presented in the adult condition, rather than to the way in
which the changes from the typical condition are brought about. With
reference to the foliar organs it is necessary to distinguish those
cases in which there is, from any cause, an augmentation in the number
of component parts of a whorl, from those in which the increase takes
place in the numbers of the whorls themselves.
FOOTNOTES:
[376] Braun, 'Pringsheim Jahrbuch f. Wiss. Bot.,' 1858, 1, p. 307, tab.
22, 23.
[377] Henfrey, 'Jour. Linn. Soc. Bot.,' vol. iii, p. 159.
[378] On the subject of chorisis or dedoublement the reader may
profitably consult Moquin-Tandon, 'Ess. sur les Dedoublements,' and the
same author in 'Ann. Sc. Nat.,' t. xxvii, p. 236. and 'El. Ter. Veget.,'
p. 337. Dunal, 'Consid. Org. Fleur.,' Montpell., 1829, p. 32, note 3. A.
de St. Hilaire in 'Ann. Sc. Nat.,' ser. 3, t. iii, p. 355, adnot.
Lindley, 'Elements of Botany,' p. 76. Asa Gray. 'Botanical Text Book.'
CHAPTER I.
MULTIPLICATION OF AXILE ORGANS, INFLORESCENCE, ETC.
By Linne an undue number of branches was designated as "plica," from the
analogy with the disease of the hair known as plica polonica: "_Plicata
dicitur planta, cum arbor vel ramus excrescit minimis intertextis
ramulis, tanquam plica polonica ex pilis, ceu instar nidi Picae, quod
vulgo a genio ortum arbitratur; frequens apud nos in Betula, praesertim
Norlandiae, in Carpino Scaniae, nec infrequens in Pinu._"[379]
By some of the older authors this condition was called polyclady. In
some cases, it would seem to be due to fungi as in the witches' brooms
(hexenbesen) of the German forests; in other instances, it is a result
of mutilation as after the operation of pollarding.
Moquin-Tandon[380] mentions a case in a grafted ash in the botanic
garden of Toulouse, where below the graft there was a large swelling,
from which proceeded more than a thousand densely-packed, interlacing
branches.
This must have been similar to the condition so commonly met with in the
birch, and frequently in the hornbeam and the thorn, and which has
prompted so many a schoolboy to climb the tree in quest of the apparent
nest. It is probable that some of the large "gnaurs" or "burrs," met
with in elms, &c., also in certain varieties of apples, are clusters of
adventitious buds, some of which might, and sometimes do, lengthen out
into branches.
An increased number of branches also necessarily arises when the
flower-buds are replaced by leaf-buds.
[Illustration: FIG. 179.--Flower stalks of _Bellevalia comosa_, nat.
size, after Morren.]
Occasionally, a great increase in the number of pedicels, or
flower-stalks, may be met with in conjunction with a decreased number
of flowers, as in the wig-plant (_Rhus Cotinus_), or the
feather-hyacinth (_Bellevalia comosa_). In these cases the supernumerary
pedicels are often brightly coloured. To this condition Morren gave the
name mischomany, from [Greek: mischos], a pedicel, a term which has not
generally been adopted.[381]
[Illustration: FIG. 180.--Tuft of branches at the end of the
inflorescence of _Bellevalia comosa_, enlarged after Morren.]
M. Fournier[382] describes a case in the butcher's broom (_Ruscus
aculeatus_), wherein from the axil of the minute leaf subtending the
flower a secondary flattened branch proceeded.
Duchartre[383] cites the case of a hyacinth which, in addition to the
usual scape, had a second smaller one by its side terminated by a
solitary flower; indeed, such an occurrence is not uncommon.
Some tulips occasionally present three or four, or more, flowers on one
inflorescence, but whether from a branching of the primary scape, or
from the premature development of some of the axillary bulbils into
flowering stems which become adherent to the primary flower-stalk,
cannot, in all cases, be determined. Certainly, in some cases examined
by me the latter was the case.[384]
Under this head, too, may be included those cases wherein an ordinarily
spicate inflorescence becomes paniculate owing to the branching of the
axis and the formation of an unwonted number of secondary buds.
Instances of this kind may be met with in willows, hazels, alders, and
other amentaceous plants. In the case of the hazel the unusual
development of male catkins sometimes coincides with an alteration in
their position, instead of being placed near the axil of a leaf; they
become terminal. Jaeger figures and describes a bunch of _Pinus
sylvestris_ bearing in one case seventy minute cones, and in another
fifty-nine. These cones preserved the same spiral arrangement among
themselves which is proper to the leaves. These latter, indeed, replaced
the strobili above.[385]
[Illustration: FIG. 181.--Increased number of male catkins in the hazel
_Corylus avellana_.]
M. Reichardt describes an analogous case in the same species, and
attributes the inordinate number of cones to a fungus (_Peridermium
pini_). In this case there were no less than 227 cones, but each one
half the size of the ordinary cones.[386]
Of a similar character is the many-headed pineapple. Among grasses such
a branching of the inflorescence is exceedingly common,--which is the
more readily understood as the normal inflorescence is in so many cases
paniculate. Cultivators have, in some instances, availed themselves of
this peculiarity, as in the Egyptian wheat or corn of abundance
(_Triticum compositum_), certain varieties of Maize, etc. Similar
exuberant growths occur in _Orchidaceae_, in _Cyperaceae_, e.g. _Carex_,
in _Restiaceae_, and indeed they may be found in any plant with a similar
form of inflorescence. In all these cases the branching begins at the
lower part of the spike, and extends from below upwards in an indefinite
manner, even although the primary inflorescence be definite.
Among the _Equisetaceae_ a similar plurality of spikes occurs often as a
result of mutilation.[387] The deviation in question might in some
instances be turned to good account, as in the _Triticum_ before
mentioned or as in the broccoli shown at fig. 182, though it must be
added that the apparent advantages are often counterpoised by some
undesirable qualities or by some circumstance which prevents us availing
ourselves of the new condition.
=Multiplication of Bulbs.=--This occurrence has been briefly alluded to
previously (see p. 84). The most curious cases are those in which one
bulb is placed on the top of another as happened in some bulbs of
_Leucoium aestivum_ described by M. Gay.[388] Irmisch described a similar
phenomenon in _L. vernum_; and Mr. Moggridge has communicated drawings
of a similar formation in the same species grown in the neighbourhood of
Mentone.
From the instances cited it is clear that branching of the inflorescence
occurs most frequently in those plants naturally characterised by a
dense compact mode of growth, whether that be definite or indefinite, as
in spikes, umbels, capitula, &c.; so that compound spikes, umbels, &c.,
are formed in the place of simple ones (see also prolification of the
inflorescence, p. 102).
[Illustration: FIG. 182.--Broccoli, with six perfect heads on one stalk
('Gard. Chron.,' 1856, Oct. 25).]
=Increased number of florets= in the individual spikelets of grasses is
also met with under some circumstances. I have seen this in _Hordeum_
and _Lolium_, and an instance is figured in _Avena_ by Dr.
Wiegmann.[389] M. Duval Jouve[390] records a similar occurrence in
_Catabrosa aquatica_, the spikelets of which contained from two to seven
flowers.[391]
FOOTNOTES:
[379] 'Phil Bot.,' Sec. 274.
[380] 'El. Ter. Veget.,' p. 392.
[381] 'Bull. Acad. Belg.,' xvii, part ii, p. 38.
[382] 'Bull. Soc. Bot. Fr.,' vol. iv, 1857. p. 760.
[383] Ibid., vol. viii, 1861, p. 159.
[384] See 'Gard. Chron.,' July, 1866, p. 656, and Clusius, 'Plant.
Rar.,' lib. 2, p. 143, _Tulipa serotina_ [Greek: polyklades], _minor_,
_&c._ Hort. Eysttett. Plant. Vern.,' fol. 12.
[385] 'Jaeger de Pini sylvestris monstrositate,' Stuttgardt, 1828.
[386] Cited in 'Bull. Soc. Bot. Fr.,' xiv, p. 265.
[387] Duval Jouve, 'Hist. Nat. Equiset. Fr.,' tab. 8, also Milde, 'Nov.
Act. Acad. Nat. Cur.,' t. xxvi, part 2. For branched inflorescence of
orchids, see 'Reichenbach Proc. Lond. Bot. Congress,' 1866, p. 121.
[388] 'Bull. Soc. Bot. Fr.,' vi, 266, vii, 457. Irmisch, 'Knollen und
Zwiebelgew.,' tab. 7, figs. 10, 11.
[389] 'Flora,' 1831, p. 5, tab. i; see also Hanstein, 'Flora,' 1857, p.
513. Schlechtendal, 'Bot. Zeit.,' xviii, p. 381.
[390] 'Bull. Soc. Bot. Fr.,' ix, p. 8.
[391] It will be seen, from what has been just said, that in some of the
cases where the axile organs, branches, &c., appear to be multiplied,
the increased number is due to subdivision rather than to renewed
formation (see Fission). Of this last description is an instance which
came under the writer's notice after the section relating to that
subject was in print, and which may therefore here be alluded to. The
instance is that of the subdivision of the leaf-like organs of
_Sciadopitys verticillata_. In one instance the pseudo leaf divided, and
from the division proceeded a little axis, bearing at its summit a
verticil of pseudo leaves. This division and formation of new axes and
verticils affords ample confirmation of the opinion thrown out by
Professor Alexander Dickson, that the apparent leaves of this plant were
really branches: see 'Revue Horticole,' 1867, and 'Report. Bot.
Congress,' London, 1866, p. 124.
CHAPTER II.
MULTIPLICATION OF FOLIAR ORGANS.
The cases referrible to this head may be ranged under two sections
according as the increase is due to plurality of ordinarily single
organs, or to an increase in the number of verticils or whorls.
When, in place of a single leaf organ two or more are really or in
appearance present the occurrence may be due to one of several causes;
among them may be mentioned an actual formation of parts in unwonted
number, hypertrophy or enation, chorisis or fission, disjunction,
adhesion of one leaf to another or to the stem, as in some of the leaves
called "geminate," wherein the two leaves, though apparently in
juxtaposition, yet originate from different parts of the stem, but by
coalescence or lack of separation produce the impression as if they
sprang from the same node. In the adult state it is not always possible
to ascertain with certainty to which of these causes the increase in the
number of leaves is due, though a clue to the real state of things may
be gained from attention to the distribution of the veins, to the
arrangement or phyllotaxy of the leaves, the size and position of the
supernumerary organs, &c.
The term "phyllomania," as ordinarily used, is applied to an unwonted
development of leafy tissue, as in some begonias where the scales or
ramenta are replaced by small leaflets, or as in some cabbage leaves,
from the surface of which project, at right angles to the primary
plane, other secondary leafy plates; but these are, strictly speaking,
cases of hypertrophy (see Hypertrophy).
Those instances in which the actual number of leaves is increased, so
that in place of one there are more leaflets, may be included under the
term "pleiophylly," which may serve to designate both the appearance of
two or more leaves in the place usually occupied by a single one, and
also those normally compound leaves in which the number of leaflets is
greater than usual.
The increased number of leaves in a whorl may well be designated as
"polyphylly," using the word in the same sense as in ordinary
descriptive botany, while "pleiotaxy" may be applied to those cases in
which the number of whorls is increased.
[Illustration: FIG. 183.--Supernumerary leaflet, _Ulmus campestris_.]
=Pleiophylly.=--As above stated, this term is proposed to designate
those cases in which there is an absolute increase in the number of
leaves starting from one particular point, as well as those in which the
number of leaflets in a compound leaf is preternaturally increased. The
simplest cases are such as are figured in the adjacent cuts, wherein, in
place of a single leaf, two are produced in the elm. In the one case the
new leaflet springs from the apex of the petiole and partially fills
the space consequent on the obliquity of the base of the leaf. In the
other it would seem as if two distinct leaves emerged from the stem in
juxtaposition. This is probably due to a lateral chorisis or subdivision
of the primitive tubercle or growing point, followed by a like
subdivision of the vascular bundle supplying it. There are certain
varieties of elm that very generally present this anomaly on their rank,
coarse, growing shoots. In these cases the new growths have the same
direction as the primary one, but in other cases the supplementary
production is exactly reversed in direction. Thus, in the common hazel
(_Corylus_) a second smaller leaf proceeding from the end of the
leaf-stalk at the base of the primary one may frequently be seen. M.
Germain de Saint Pierre records an instance in a mulberry leaf, from the
base of which proceeded a large leafy expansion divided into two
tubular, horn-like projections, and in the centre a thread-like process
representing the midrib and terminated by a small two-lipped limb.[392]
Dr. Ferdinand Mueller speaks of a leaf of _Pomaderris elliptica_ as
bearing a secondary leaf on its under surface.[393]
[Illustration: FIG. 184.--Supernumerary leaf, _Ulmus montana_.]
[Illustration: FIG. 185.--Supernumerary leaf of hazel.]
The leaves of _Heterocentron macrodon_ have likewise been observed
occasionally to produce leaflets from their upper surface.
To this production of leaves from leaves the late Professor Morren
applied the term "autophyllogeny."[394] The Belgian botanist figures a
small perfect leaf springing from the nerves of the upper surface of the
primary leaf in a species of _Miconia_. As in the hazel, the direction
of the adventitious leaf is inversely that of the primary one, the upper
surface of the supernumerary leaflet being turned towards the
corresponding surface of the normal leaf. A similar occurrence took
place in _Gesnera zebrina_, but the new growth in this case sprang from
the lower face of the leaf. Morren explains the appearances in question
by supposing that the supplementary leaf is one of a pair belonging to a
bud borne on a slender stalk. This stalk and one of the bud-leaves are
supposed to be inseparably united with the primary leaf. But there is
no reason at all for supposing the existence of adhesion in these cases;
no trace of any such union is to be seen. A much more natural
explanation is that, from some cause or another, development at the apex
of the petiole or on the surface of the nerves, instead of taking place
in one plane only, as usual, takes place in more than one, thus showing
the close relationship, if not the intrinsic identity, between the
leaf-stalk and its continuation, the midrib, with the branch and its
subdivisions. The form of the leaf-stalk and the arrangement of the
vascular bundles in a circle in the case of the hazel, before alluded
to, bear out this notion. Such cases are significant in reference to the
notion propounded by M. Casimir de Candolle, that the leaf is the
equivalent of a branch in which the upper portion of the vascular circle
is abortive.[395]
Compound leaves, as has been stated, occasionally produce an extra
number of leaflets; one of the most familiar illustrations of this is in
the case of the four-leaved shamrock (_Trifolium repens_), which was
gathered at night-time during the full moon by sorceresses, who mixed it
with vervain and other ingredients, while young girls in search of a
token of perfect happiness made quest of the plant by day. Linne, who in
this matter, at any rate, had less than his usual feeling for romance,
says of the four-leaved trefoil that it differs no more from the
ordinary trefoil than a man with six fingers differs from one provided
with the ordinary number. It should be stated that five and six
adventitious leaflets are found almost as frequently as four.
Walpers describes a case where the leaf of _T. repens_ bore seven
leaflets. Schlechtendal alludes to a similar increase in number in
_Cytisus Laburnum_, and many other instances might be cited.
For figures or descriptions of four-leaved shamrocks the reader
is referred to Lobel, 'Stirp. Advers.,' Nov., p. 382.
Tabernaemontanus 'Krauterbuch,' S. 222. Schlechtendal, 'Bot.
Zeit.,' ix, p. 583, xiv, p. 71. Maugin, 'Bull. Soc Bot. Fr.,'
1866, t. xiii, p. 279. See also Cramer, 'Bildungsabweich,' p.
92. Walpers, 'Linnaea,' 1840, p. 362 (7-leaved). Schlechtendal,
'Bot. Zeit.,' 1844, p. 457, _Cytisus_. Wigand, 'Flora,' 1856,
p. 706.
Frondiferous leaves have much the appearance of branches provided with
leaves, and they may be compared with those instances in which an
adventitious bud is placed on the surface or edges of the leaves, as in
_Gesnera_, _Cardamine_, &c. In truth, the two conditions merge one into
the other, as in some begonias, where the ramenta often become leaf-like
and bear small bulbils in the axil.
When frondiferous leaves die the appendages die also, but when a true
bud has been formed on a leaf it does not of necessity die with the leaf
that bears it, but separates from it and continues to grow
independently.
=Increased number of stipules, spathes, &c.=--Seringe relates the
occasional presence of two or three additional stipules upon the
leaf-stalks of _Salix fragilis_, and even makes a variety (_Salix
pendula_, var. _multistipulata_).
An increase in the number of the spathes has been often noticed in
Arads[396]. Prof. Alex. Braun has studied this subject in some
detail[397]. In _Calla palustris_ the shoot which continues the growth
of the plant proceeds from the axil of the last leaf but one; the very
last leaf producing no bud, but if accidentally a shoot is developed in
this latter situation it produces flowers at once. No leaves are formed,
but, on the contrary, two or three spathes surround the spadix, so that
the presence of an increased number of spathes in this plant is
associated with the development of a side shoot from the axil of the
last leaf, the situation whence, under natural circumstances, no shoot
at all issues. The supernumerary spathes are not always on the same
level, but may be separated by a considerable interval. They vary very
much in size, and sometimes assume the form and appearance of leaves.
Similar anomalies occur in other Arads as _Arum maculatum_, _Richardia
aethiopica_, and _Anthurium Scherzerianum_, frequently combined with a
leaf-like appearance of the spathes and sometimes with a subdivision of
the spadix into two or three branches.
Engelmann relates the occurrence of an increased number of glumes in
_Bromus velutinus_ associated with suppression of the flowers.
=Polyphylly.=--As previously explained, this term is here applied to
those cases in which the members of any particular whorl are increased
in number, the whorls themselves not necessarily being augmented.
The simplest cases of this kind are those in which we meet with an
unusual number of leaves in a whorl.
=Increased number of leaves in a whorl.=--This may arise from actual
multiplication, or from lateral chorisis, or fission. The true nature of
the case may usually be ascertained by an examination of the
distribution of the veins of the leaves, or of the fibrous cords of the
stem, by the relative position of the supernumerary organs, &c.
Among plants with normally opposite leaves the following occasionally
produce them in whorls of three:--_Lonicera brachypoda_, _L. Xylosteum_,
_Weigela rosea_, _Cornus mas_, _Vinca minor_, &c.
_Paris quadrifolia_ may frequently be met with five leaves in its whorl,
or even six.[398]
=Increased number of bracts.=--This is not of infrequent occurrence; one
of the most curious instances is that recorded by Mr. Edwards[399] in
_Cerastium glomeratum_, where, in place of the usual pair of bracts at
the base of the head of flowers, there was a whorl of six or eight,
forming an involucre. The flowers in this case were apetalous and
imperfect.
=Polyphylly of the calyx.=--This may occur without any other
perceptible change, while at other times the number of the other parts
of the flower is proportionately increased. In a flower of a plum six
sepals in place of five sometimes exist; a precisely similar occurrence
in the flowers of the elder (_Sambucus_), the _Fuchsia_, and of
_OEnanthe crocata_, may occasionally be met with. In the latter case,
indeed, there are sometimes as many as ten segments to the calyx, and
this without the other parts of the flower being correspondingly
augmented. Among monocotyledons a similar increase is not uncommon, as
in _Tulipa_, _Allium_, _Iris_, _Narcissus_, &c.
In some plants there seems to exist normally much variation in the
number of parts; thus in some species of _Lacistema_ in adjacent flowers
the calyx may be found with four, five, or six segments.
Most of these cases of polyphylly affecting the calyx may be explained
by lateral chorisis or fission.
=Polyphylly of the corolla.=--This may happen in connection with similar
alterations in the calyx and stamens, or sometimes as an isolated
occurrence. In the latter case it may be due to lateral chorisis, to
substitution, or to the development of organs usually suppressed; thus,
when in aconites we meet with four or five horn-like nectaries (petals)
instead of two only, as usual, the supernumerary ones are accounted for
by the inordinate development of parts which ordinarily are in an
abortive or rudimentary state only. This is borne out by what happens in
_Balsamineae_. In the common garden balsam the fifth petal is
occasionally present, while in _Hydrocera triflora_ this petal is always
present.
In a flower of a _Cyclamen_ recently examined there were ten petals in
one series, the additional five being evidently due to the subdivision
of the five primary ones; the natural circular plan of the flower was
here replaced by an elliptical one. A similar occurrence takes place in
the flowers of maples (_Acer_), which sometimes show an increased number
of parts in their floral whorls and an elliptical outline. Whether the
additional organs in this last case are the result of complete lateral
chorisis or of multiplication proper I do not know.
Orchids are very subject to an increase in the number of their labella.
As illustrations may be cited an instance recorded by Mr. J. T.
Moggridge in a flower of _Ophrys insectifera_, and in which there were
two labella without any other visible deviation from the ordinary
conformation.[400]
I am indebted to Mr. Hemsley for the communication of a similar specimen
in _O. apifera_, in which there were two divergent lips, each with the
same peculiar markings. One of the sepals in this flower was adherent to
one of the lateral petals. This augmentation of the labella depends
sometimes on the separation, one from the other, of the elements of
which the lip is composed, at other times on the development, in the
guise of lips, of stamens which are usually suppressed (see p. 380).
The following enumeration will suffice to show the genera in which an
increased number of petals or perianth-segments in any given whorl most
frequently occurs.
Anemone!
Ranunculus!
Aconitum!
Raphanus.
Bunias.
Saponaria.
Dianthus!
Pelargonium!
Hibiscus.
Fuchsia.
Sarothamnus!
Lotus!
Ulex!
Prunus!
Trifolium.
OEnanthe and Umbellif. pl.!
Sambucus!
Bryonia.
Campanula.
Solanum.
Veronica.
Cyclamen!
Primula!
Anagallis!
Plumbago.
Jasminum.
Syringa!
Tradescantia.
Iris.
Tigridia.
Narcissus.
Tulipa.
Convallaria!
Paris!
Hyacinthus!
Allium!
Ornithogalum.
Orchideae, sp. pl.!
For other illustrations see multiplication of whorls, petalody;
see also Moquin, loc. cit., p. 350. Engelmann, loc. cit., p.
20, Sec. 18. Cramer, loc. cit., p. 25.
=Polyphylly of the androecium.=--An increased number of stamens
frequently accompanies the corresponding alterations in other whorls,
and seems, if anything, to be more frequent among monocotyledonous
plants than among dicotyledonous ones; thus, we occasionally find
tetramerous flowers in _Crocus_, _Hyacinthus_, _Tulipa_, _Iris_,
_Tigridia_, &c., and more rarely in _Yucca_ (_Y. flexilis_[401]).
The increased number of stamens in a single whorl may result from a
development of organs usually suppressed, and constitute a form of
regular peloria as in _Linaria_, wherein a fifth stamen is occasionally
met with. Among normally didynamous plants such numerical restitution,
so to speak, is not unusual; thus, in _Veronica_ four and five stamens
occur. Fresenius has seen five stamens in _Lamium_, _Mentha_,
_Chelone_;[402] Bentham in _Melittis_, and other instances are cited
under the head of peloria. Chorisis may also serve to account for some
of these cases; thus, Eichler[403] figures a flower of _Matthiola annua_
with five long stamens instead of four; one of the long pairs of stamens
has here undergone a greater degree of repetition than usual. De
Candolle[404] cites and figures a curious form of _Capsella
Bursa-pastoris_ sent him by Jacquin, and which was to some extent
reproduced by seed. In the flowers of this variety there were no petals,
but ten stamens; hence De Candolle inferred that the petals were here
replaced by stamens, but Moquin[405] objects, and with justice, to this
view, as the ten stamens are all on the same line; he considers the
additional stamens to be the result of chorisis. Buchenau[406] mentions
the presence of seven stamens in another Crucifer, _Ionopsidium
acaule_. Here the supernumerary organ was placed between two of the long
stamens. The effect of chorisis in producing an augmentation of parts is
well seen in some plants that have some of their flowers provided with
staminodes or abortive stamens, and others with clusters or phalanges of
perfect stamens. Thus, in the female flowers of _Liquidambar_ there are
five small staminodes without anthers, whereas in the male flower the
stamens are numerous and grouped together in phalanges, so that the
relation of simple to compound stamens is in this case readily seen, as
also in many _Malvaceae_, _Sterculiaceae_, _Byttneriaceae_, _Tiliaceae_, and
_Myrtaceae_. It is probably the idea of splitting or dilamination
involved in the word chorisis that has led many English botanists to
hesitate about accepting the notion. Had they looked upon the process as
identical with that by which a branched inflorescence replaces an
unbranched one, or a compound leaf takes the place of a simple one, the
objections would not have been raised with such force. The process
consists, in most cases, not so much in actual cleavage of a
pre-existing organ as in the development of new-growing points from the
old ones.
An illustration given by Moquin from Dunal[407] goes far to support the
notion here adopted. The majority of the stamens of laurels (_Laurus_)
have, says M. Dunal, on each side of the base of their filaments a small
glandular bifid appendage; these excrescences are liable to be changed
into small stamens. The male flowers have a four-leaved calyx, and
sometimes eight stamens, each with two glands, four in one row, opposite
to the sepals, four in a second series alternating with the first. More
generally two of the stamens are destitute of glands, but have in their
place a perfectly developed stamen, so that in these latter flowers
there are twelve stamens.
M. Clos[408] mentions a flower of rue (_Ruta_) wherein there were two
stamens joined together below and placed in front of a petal, as in
_Peganum_.
Buchenau[409] mentions a flower of _Lotus uliginosus_ in which there
were eleven stamens, namely, two free and nine monadelphous; and
Hildebrand describes an analogous increase in a flower of _Sarothamnus
scoparius_ in which, in conjunction with a seven-toothed calyx, there
were two carinas and fourteen stamens. It would seem probable in this
case that there was a coalescence of two flowers at an early date and
consequent suppression of some of the parts of the flower. Whether this
was the case or not in this particular illustration, it is nevertheless
certain that many of the recorded instances of increased number in the
organs of a flower are really the results of a fusion of two or more
flowers, though frequently in the adult state but few traces of the
coalescence are to be seen.
=Polyphylly of the gynoecium.=--Moquin[410] remarks that, as the
pistils are, generally speaking, more or less subject to pressure, owing
to their central position, and it may be added owing to their later
development, than the other parts of the flower, they are more subject
to suppression than to multiplication; nevertheless, augmentation in the
number of carpels does occasionally take place, especially when the
other parts of the flower are also augmented in number. Sometimes this
increase in the number of carpels is due to pure multiplication, without
any other change. At other times the increase is due to a substitution
of stamens or other organs for carpels (see Substitutions). In other
cases the augmentation seems to be due to the development of parts
usually suppressed; for instance, in _Antirrhinum_, where there are
usually only two carpels present, but where, under peculiar
circumstances, five may be found--thus rendering the symmetry
complete.[411] In _Papilionaceae_, wherein usually only one carpel is
developed, we occasionally find two, or even more, as in _Wistaria_,
_Gleditschia_, _Trifolium_, &c. In _Prunus_ and _Amygdalus_ from two to
five carpels are occasionally to be found,[412] in _Mimosa_ five, in
_Umbelliferae_ three to five; in some composites, _e.g._ _Spilanthes_,
five carpels have also been noticed; in _Cruciferae_ three and four, in
grasses three.[413] The double cocoa-nut affords an illustration of the
development of two carpels out of three, one only generally arriving at
perfection. Triple nuts (_Corylus_) also owe their peculiarity to the
equal development of all three carpels which exist in the original
flower, but of which, under ordinary circumstances, two become abortive.
It is necessary, however, to distinguish these cases from those in which
two embryos are developed in one seed.
The following list may serve to show in what genera this change has been
most frequently noticed, and it may be said in general terms that
_Cruciferae_, _Umbelliferae_, and _Liliaceae_, are the orders most
frequently affected. Cases of peloria are not included in the subjoined
list.
Nigella.
Aquilegia.
Paeonia!
Delphinium!
Iberis.
Diplotaxis.
Lunaria.
Ricotiana.
Octadenia.
Draba!
Lepidium.
*Cheiranthus!
Dianthus.
Brassica!
Parnassia.
*Acer!
Ptelea.
Citrus!
Philadelphus.
Prunus!
Amygdalus!
Crataegus!
Fuchsia!
Trapa!
Cassia.
Cercis.
Medicago.
*Phaseolus!
Wistaria.
Gleditschia.
Affonsea.
Trifolium!
Archidendron.
Mimosa.
Robinia.
Diphaca.
Coesalpinia.
Vicia.
Anthyllis.
Cucurbita.
Passiflora!
Sambucus!
*OEnanthe!
Daucus!
Angelica!
Heracleum!
Silaus.
Carum.
Thysselinum.
Campanula!
Spilanthes.
Chrysanthemum.
Anagallis.
Primula!
Fraxinus!
Lycium.
Cobaea.
Datura!
Solanum!
Sesamum.
Sideritis.
Coleus.
Veronica!
*Digitalis!
Antirrhinum!
Linaria.
Gloxinia!
Symphytum.
Anchusa.
Polygonum.
Euphorbia.
Cneorum.
Mercurialis!
Chenopodium.
Suaeda.
Beta.
Corylus!
Lambertia.
Cocos!
Tigridia.
Tulipa!
Iris!
Narcissus!
Allium!
Ornithogalum.
Gagea!
Tradescantia!
Schoenodon.
Bambuseae.
A few additional references may here be given to papers where
an increased number of carpels is described:--Engelmann, 'De
Antholys,' Sec. 17, p. 19. Bernhardi, 'Flora,' 1838, p. 129.
Schkuhr., 'Bot. Handb.,' t. 179. Godron, 'Ann. Sc. Nat.,' ser.
5, vol. ii, p. 280, tab. xviii, _pluricarpellary Crucifers_.
Weber, 'Verhandl. Nat. Hist. Vereins. Rhein. Pruss.,' &c.,
1860, _Cerasus_, &c., &c. Baillon, 'Adansonia,' iv, p. 71,
_Trifolium_. Schlechtendal, 'Bot. Zeit.,' xv, p. 67, _Datura_,
three-celled fruit; 'Bot. Zeit.,' xiii, p. 823, _Phaseolus_,
double pistil--a common case. Cramer, 'Bildungsabweich,' p. 99,
reference to several leguminous plants with polycarpellary
pistils. Munro, Gen., 'Linn. Trans.,' vol. xxvi, p. 26,
_Bambuseae_. Alph. de Candolle, 'Neue Denkschrift,'
_Cheiranthus_. Schimper, 'Flora,' 1829, ii, p. 433. Wigand,
'Bot. Untersuch.' Fleischer, 'Missbild. Cultur Pfl.' Cramer,
'Bildungsabweich,' p. 65, _Umbelliferae_.
=Polyphylly of the flower in general.=--Although, for the sake of
convenience, multiplication has here been treated of as it affects the
members of individual whorls of the flower, yet it must be remembered
that, in general, the augmentation is not confined to one whorl, but
affects several; thus, if the sepals are increased, the petals are
likely to be so likewise, and so forth. One of the most curious
illustrations of this is that recorded by Mr. Berkeley[414] in a plum,
wherein there was an increased number of sepals, a corresponding
augmentation in the petals, while the pistil was composed of two and
sometimes three carpels distinct from the calyx and from each other. In
the flowers there did not appear to be any definite relation in the
position of the parts either with reference one to another or to the
axis.
[Illustration: FIG. 186.--Plum. Increased number of parts in the
calycine, corolline, and carpellary whorls respectively.]
In _Primulaceae_ this general augmentation has been frequently
noticed.[415]
Among _Orchideae_ the instance related by Dr. Seubert is worth alluding
to here. This botanist observed and figured a flower of _Orchis
palustris_ with tetramerous arrangement of parts, that is to say there
were four outer segments to the perianth, four petals, of which two
were lip-like, four stamens, three of which were rudimentary, and an
ovary with four parietal placentae.[416]
The following list will serve to show in what plants this general
augmentation of parts has been observed most frequently:
Ranunculus.
Clematis!
Delphinium.
Brassica!
Ruta.
Acer!
Prunus!
Rosa!
Rubus.
Philadelphus!
Chrysosplenium.
Umbelliferae, sp. pl.!
*Fuchsia!
OEnothera.
Adoxa.
Bryonia.
Cucumis!
Campanula!
Sambucus!
*Primula!
Anagallis!
Lycium.
Solanum.
Symphytum.
Syringa!
Linaria.
Chenopodium.
*Paris!
Convallaria!
Allium.
*Lilium!
*Tulipa!
Ornithogalum.
*Gagea!
Tradescantia!
Orchideae, sp. pl.!
=Increased number of ovules or seeds.=--This appears not to be of very
frequent occurrence, at least in those plants where the number of these
organs is normally small; where, as in _Primula_, the ovules and seeds
are produced in large quantities, it is not practicable to ascertain
whether the number be augmented or not in any particular case. Very
probably, the attachment or source of origin of the ovules determines,
in some measure, their number. Thus, in the case of marginal
placentation the number must be limited by the narrow space from which
they proceed, whereas in parietal and free central placentation the
ovules are generally numerous. In the latter case, however, it will be
remembered that solitary ovules are not rare. An increased number of
ovules is generally remarked in conjunction with some other change, such
as a foliaceous condition of the carpel, in which the margins are
disunited. In such cases the ovules may occupy the margin or may be
placed a short distance within it, as in the case of some open carpels
of _Ranunculus Ficaria_,[417] and in which two ovules were borne in
shallow depressions on the upper or inner surface of the open carpel and
supplied with vascular cords from the central bundle or midrib. The
outer coating of the ovule here contained barred or spiral fusiform
vessels derived from the source just indicated.
In the very common cases where the pistil of _Trifolium repens_ becomes
foliaceous (see Frondescence), the outer ovules are generally two or
more instead of being solitary. So, also, in the Rose with polliniferous
ovules (see p. 274). Among _Umbelliferae_ affected with frondescence of
the pistil a similar increase in the number of ovules takes place. It
will be borne in mind that in most, if not all, these cases the
structure of the ovule is itself imperfect.[418]
What are called in popular parlance double almonds or double nuts
(_Corylus_) are cases where two seeds are developed in place of one.
In the 'Revue Horticole,' 1867, p. 382, mention is made of a bush which
produces these double nuts each year--in fact, it never produces any
single-seeded fruit. The plant was a chance seedling, perhaps itself the
offspring of a double-seeded parent. It would be interesting to observe
if the character be retained by the original plant, and whether it can
be perpetuated by seed or by grafting.
It is necessary to distinguish in the case of the nut between additional
seeds or ovules, as just described, and the double, triple, or fourfold
nuts that are occasionally met with, and which are the result either of
actual multiplication of the carpels or of the continued development of
some of the carpels which, under ordinary circumstances cease to grow
(see _ante_, p. 364). In the case of a ripe nut with two seeds it might
be impossible to tell whether the adventitious seed were the product of
multiplication, or whether it belonged, in the first instance, to the
same carpel as that producing the fellow-seed, or to a different and now
obliterated ovary. In all probability, however, the second seed would be
accounted for by the development of two seeds in one carpellary cavity.
There is still another condition occasionally met with in the almond,
and which must be discriminated from the more common multiplication of
the seed, and which is the multiplication of the embryos within the
seed, and which furnishes the subject of the succeeding paragraph.
=Increased number of embryos.=--A ripe seed usually contains but a
single embryo, although in the ovular state preparation is commonly made
for more; and, indeed, in certain natural orders plurality of embryos in
the same seed does occur, as in _Cycadeae_ and _Coniferae_. In the seeds
of the orange (_Citrus_), in those of some _Euphorbiaceae_, &c., there
are frequently two or more additional embryos. A similar occurrence has
been recorded in the mango, for a specimen of which I am indebted to the
Rev. Mr. Parish, of Moulmein.[419]
Plurality of embryos has also been observed in--
Raphanus sativus.
*Citrus Aurantium!
Diosma, sp.
Hypericum perforatum.
Triphasia aurantiaca.
*AEsculus Hippocastanum!
Euonymus latifolius.
*Mangifera indica!
Eugenia Jambos.
Amygdalus vulgaris!
Vicia, sp.
Cassia, sp.
*Viscum album!
Daucus Carota.
Ardisia serrulata!
Cynanchum nigrum.
fuscatum.
Euphorbia rosea.
Coelebogyne ilicifolia.
Allium fragrans.
Funckia, sp.
Carex maritima.
Zea Mays.
See Schauer's translation of Moquin-Tandon, 'El. Terat.
Veget.,' p. 245, adnot., and 'Al. Braun Polyembryonie.'
=Increased number of the cotyledons.=--Although the presence of one or
of two cotyledons in the embryo is generally accepted as a valuable
means of separating flowering plants into two primary groups, yet, like
all other means of discrimination, it occasionally fails, and, indeed,
almost always requires to be taken in conjunction with some other
character. There are cases among flowering plants where the embryo is
homogeneous in its structure, there are others in which the number of
the cotyledons is more than two. Thus, in some seeds of _Cola acuminata_
the cotyledons vary in number from two to five. I have not been able to
ascertain precisely whether this multiplication of the cotyledons is
characteristic of all the seeds of particular trees, or whether some
only are thus affected. Some fruits that I examined bore out the latter
view, as in the same pod were seeds with two, three, and four cotyledons
respectively.