In _Bouchea hyderabadensis_ I have seen the inflorescence more than usually branched and covered with little tufts of bracts, without a trace of true flower. A similar condition seems not infrequent in _Gentiana Amarella_, as I have not only met with the plant myself in this condition, but have been favoured with specimens by Mr. Pamplin, Mr. Darwin, and others. In _Phyteuma spicatum_ an a.n.a.logous appearance has been recorded.

Among Griffith's collections from Affghanistan is a species of willow (_Salix_) in which the inflorescence replaced by a much branched panicle, bearing a quant.i.ty of minute bracts, in the axils of which nestle numerous small buds. In another specimen the inflorescence preserves its usual catkin-like shape, but the flowers are replaced by little tufts of leaves. M. Germain de Saint Pierre mentions a case wherein the flowers of _Alisma parna.s.sifolia_ were completely replaced by leaf-buds.[155]

[Ill.u.s.tration: FIG. 79.--Spikelets of _Willedenovia_, composed entirely of scales to the exclusion of flowers.]

[Ill.u.s.tration: FIG. 80.--Rose Willow, _Salix_, sp.]

Here, also, may be mentioned the curious aggregations of scales which occur in some gra.s.ses, in _Restiaceae_, _Juncaceae_, and other orders, in which the inflorescence is made up of collections of scales or bracts with no trace of floral structure. Fig. 79 shows this in a species of _Willdenovia_, and a very good example is figured in a bamboo, _Pseudostachyum polymorphum_, by General Munro.[156]

"Rose willows" (fig. 80) owe their peculiar appearance to a similar cause, the scales of the catkin being here replaced by closely crowded leaves. These aggregations of scales or leaves are not confined to the inflorescence, but may be found in other parts of the plant, and may be frequently met with in the willow, birch, oak, &c., generally as the result of insect puncture. On the other hand, the production of leaves or leaf-buds in place of flowers is, as is well known, generally the consequence of an excess of nutrition, and of the continuance rather than of the arrest of vegetative development.[157] It has even been a.s.serted that a flower-bud may be transformed into a leaf-bud by removing the pistil at a very early stage of development, but this statement requires further confirmation.[158]

=Viviparous plants.=--The spikelets of certain gra.s.ses are frequently found with some of their const.i.tuent parts completely replaced by leaves, like those of the stem, while the true flowers are usually entirely absent. A shoot, in fact, is formed in place of a series of flowers. In these cases it generally happens that the outermost glumes are changed, sometimes, however, even the outer and inner paleae are wholly unchanged, while there is no trace of squamulae or of stamens and pistils within them, but in their place is a small shoot with miniature leaves arranged in the ordinary manner.

The gra.s.ses most commonly affected in this manner are _Dactylis glomerata!_, _Poa bulbosa!_, _Poa annua!_, _P. trivialis!_, _pratensis!_, _alpina!_, _angustifolia_, and _laxa_, _Cynosurus cristatus_, _Festuca nemoralis_, _F. ovina!_, _Glyceria fluitans!_, _Gl.

aquatica_, _Aira alpina!_, _caespitosa!_, _Phleum phalaroides_, _Lolium perenne!_, _Alopecurus pratensis!_, _Agrostis alba_, _Holcus mollis!_

[Ill.u.s.tration: FIG. 81.--Portion of panicle of _Aira vivipara_ and separate floret.]

From an examination of the structure of viviparous gra.s.ses Von Mohl was led to the conclusion that the lower palea is to be considered as a bract, and not a perianthial leaf, because the base of the palea surrounds the stem or axis of the spikelet entirely, and both its margins cohere towards its lower extremity.[159]

A similar condition occurs not infrequently in _Polygonum viviparum_, and in _Juncaceae_, _Cyperaceae_, &c.

In the genus _Allium_ an a.n.a.logous formation of little buds or bulbils takes place in lieu of flowers; this is specially the case with _A.

vineale_, the flowers of which are rarely seen.

Other ill.u.s.trations of a similar character, where the advent.i.tious leaf-buds are mixed in amongst the flower-buds, are cited under the head of Prolification of the Inflorescence.

=Formation of buds on leaves.=--The formation of little bulbs upon the surfaces or edges of leaves, forming what are called viviparous leaves, has long been familiar to botanists amongst Alliums. Professor Alexander Braun,[160] who has paid much attention to this subject, divides cases of this kind according to the position of the buds; thus, for instance, they are sometimes formed upon the upper portion of the leaf or petiole, as in many ferns, in _Nymphaea guineensis_, some _Arads_, &c. The same condition has been met with as a teratological occurrence in the leaves of _Cardamine pratensis_, _Hyacinthus Pouzolzii_, _Drosera intermedia_,[161] _Arabis pumila_, _Chelidonium majus_, _Chirita sinensis_,[162] _Episcia bicolor_,[163] _Zamia_, &c.[164] Many species of _Begonia_ possess the power of emitting buds from the petioles and veins of the leaf; the little ramenta or scales which so plentifully beset the surface of some of these plants likewise, in some instances, pa.s.s gradually into leaves. _B. phyllomaniaca_, Mart., is the species best known as manifesting this tendency, but others have it also.[165]

Buds are also very often formed upon the margins of the leaf, the best known instance of which occurs in _Bryophyllum calycinum_; Weinmann[166] figures an instance of this kind in _Alchemilla minima_, or they may occur upon the lower surface of the leaf, as in _Ornithogalum scilloides_ and _longe-bracteatum_. M. Duchartre[167]

mentions a case in the tomato in which the leaves gave origin to small leaf-bearing branches, which, of course, must have originated from buds, just in the same way as in the _Drosera_ before mentioned.

[Ill.u.s.tration: FIG. 82.--Formation of shoot on leaf of _Episcia bicolor_.]

Gardeners occasionally avail themselves of this formation of buds from leaves to propagate plants, _e.g._ _Hoya_, _Gesnera_, _Gloxinia_, &c.

=Formation of buds in the pith.=--This is said to be a normal condition in the curious _Stangeria paradoxa_,[168] and Mr. Berkeley records an instance of this in sea-kale[169] (fig. 83) where the crown had been injured, and buds were seen sprouting from its centre.

[Ill.u.s.tration: FIG. 83.--Advent.i.tious buds in sea kale.]

[Ill.u.s.tration: FIG. 84.--Hyacinth bulb cut across to induce the formation of new bulbs.]

[Ill.u.s.tration: FIG. 85.--Showing the formation of new bulbs on the cut edges of an old hyacinth bulb.]

It will be remarked that the advent.i.tious production of buds, like that of roots, is very often consequent on decay or injury. The Dutch bulb-growers have availed themselves of this latter circ.u.mstance in the propagation of hyacinths. Mr. Fortune, who published some articles on this subject in the 'Gardener's Chronicle,'[170] describes two special modes as adopted by these skilful horticulturists--the one to make two or three deep cuts at the base of the bulb, destroying the nascent flower-stalk when, after a time, small bulbs are formed along the edges of the cut surfaces (figs. 84, 85). The other method is effected by scooping out the interior of the base of the bulb, thus leaving exposed the cut ends of the sheathing leaves arranged concentrically; along these lines the new bulbs are, after some time, formed in great numbers (fig. 86).

[Ill.u.s.tration: FIG. 86.--Showing the production of small bulbs on the inner surface of the scooped-out bulb of hyacinth.]

For the formation of supernumerary leaves on the surface of the normal one, see Multiplication and Hypertrophy.

=Production of gemmae in place of spores.=--An instance of this is recorded by Dr. Montagne[171] in the case of a moss, _Encamptodon perichaetialis_, in which, in the interior of the capsule, in lieu of spores numerous minute gemmae of the same nature as those in the cup of _Marchantia_ were seen.

=Formation of flowers on leaves.=--It is very doubtful whether a flower-bud has ever been found actually on a leaf. Mere adhesion of the pedicels of the leaf, such as happens in _Ruscus_, in _Helwingia_, _Erythrochiton hypophyllanthus_, and a few other plants, is, of course, not really to be considered in the light of an actual growth from the leaf, and it is very doubtful in the present state of our knowledge whether the case of the Nepaul barley should find a place here, but for convenience sake it is placed in this section, as it is uncertain at present where it properly belongs.

[Ill.u.s.tration: FIG. 87.--Three-lobed end of outer palea of Nepaul barley bearing supplementary florets.]

[Ill.u.s.tration: FIG. 88.--Three spikelets of Nepaul barley.]

[Ill.u.s.tration: FIG. 89.--Lip of outer palea of Nepaul barley.]

[Ill.u.s.tration: FIG. 90.--Supplementary rachillus or outer palea of Nepaul barley bearing florets.]

[Ill.u.s.tration: FIG. 91.--Diagram showing arrangement of supplementary rachillus and florets.]

[Ill.u.s.tration: FIG. 92.--Supplementary floret of Nepaul barley; palea removed.]

This curious plant has been described and figured by Irmisch in the 13th volume of the 'Linnaea,' p. 124, t. iv; also by Professor Henslow, 'Hooker's Journal of Botany,' 1849, vol. i, p. 33, tabs. 2, 3. The lower palea of this plant forms an inverted flower-bud upon its midrib. In some fresh specimens which I have lately examined I find the structure to be as follows:--On each notch of the rachis there are three spikelets (fig. 88), each one-flowered, and each provided with two linear glumes; the outer palea in all cases is three-lobed at the summit, the central lobe being oblong and hollow, forming a kind of hood (figs. 87-89), and covered with hairs, which are directed downwards towards the centre of the plant. The two lateral lobes are more pointed than the central one; like it they are provided with hairs, but the hairs, in this case, are turned away from the centre of the plant. The cavity of the side lobes is generally empty, but that of the central lobe is occupied by a very slender stalk, which is apparently the termination of the midrib, but which is bent inwards at an acute angle, so as to occupy the hollow s.p.a.ce (figs. 90-91). On this slender axis are developed two florets, more or less imperfect in their structure. Only one of the florets that I have seen contained a perfect ovary. The tips of the lateral lobes of the paleae in the primary flower are sometimes extended into a long awn.

A similar awn may also be occasionally found on the tips of the paleae of the rudimentary florets. The occurrence of an advent.i.tious axial structure with rudimentary flowers has been adduced in support of the opinion that the lower paleae is, at least so far as its midrib is concerned, an axial rather than a foliar structure, but in the present uncertain state of our knowledge as to the morphology of gra.s.ses it is hazardous to risk any explanation founded on so exceptional a case as that of the Nepaul barley.[172]

=Production of flower-buds in place of leaf-buds.=--Under natural circ.u.mstances this does not appear to be of so common occurrence as the change above alluded to, but by the art of the gardener the change is often effected. In rhododendrons and in peach trees and roses I have met with this change occurring without human agency. The means adopted by the gardener are such as check the luxuriance of the leaf-shoots,[173]

and this is effected in various ways, as by continuous "pinching" or removal of the leaf-buds, by pruning, ringing the bark, confining the roots, limiting the supply of nutriment, and other means all based on the same principle. Some of the Cape bulbs (_Cyrtanthus_) are known not to produce their flowers till their leaves have received, in some manner, a check. Fires which often destroy the herbage thus have the effect of throwing the plant into bloom. A very remarkable instance is recorded of the production of flower-buds after an injury to the leaf-buds in the 'Bulletin of the Botanical Society of France,' vol. ix, p. 146. It appears that during the war of the French against the Arabs in Algiers, the latter planted several hundreds of Agaves with a view to obstruct the pa.s.sage of the French cavalry. The soldiers hacked these plants with their sabres, and cut out the central tuft of leaves, or the heart, as gardeners call it. The following season almost every one of these Agaves sent up their large handsome flower-spikes. It is well known that, under ordinary circ.u.mstances, these plants do not flower except at long intervals of time.

=Presence of flowers on spines.=--That the spine, as a contracted branch, should occasionally produce flowers is not to be wondered at, though the occurrence is by no means common. M. Baillon showed at a meeting of the Botanical Society of France ('Bulletin,' vol. v, 1858, p.

316) a branched spine of _Gleditschia_ bearing a flower at the end of each of the sub divisions. This was, therefore, strictly a.n.a.logous with those cases in which the peduncle is normally spiney.

=Formation of flower-bud on the petals.=--An instance of this, it is believed, the only one on record, is cited in the 'Gardeners' Chronicle'

for 1865, p. 760, by the Rev. M. J. Berkeley, who describes the formation of a flower-bud on the surface of a petal of _Clarkia elegans_. Reasoning from a.n.a.logy there seems no reason why buds should not be formed on the petals as well as on the leaves.

=Formation of buds on fruits.=--This is a point of some moment with reference to the share which the axis takes in the production of "inferior" fruits. A very frequent malformation in pears is one wherein a second pear proceeds from the centre of the first, and even a third from the centre of the second.[174] Pears are occasionally also observed arising either from the axils of the sepals of the primary pear or from the axil of leaves originating on the outer surface of the fruits--using the term fruit in its popular sense. These cases afford strong confirmation of the view that the outer portion of the so-called fruit in these plants is rather to be considered as an expansion and hollowing-out of the flower-stalk, than as formed from the calyx-tube.

It is noteworthy that the true carpels and seeds are frequently entirely absent in these cases.[175] Further reference to these fruits will be made under the head of Hypertrophy.

M. Trecul has described and figured an instance in a species of _Prismatocarpus_, in which a second flower proceeded from the axil of a bract attached to the side of the fruit of the first flower.[176] A similar growth was observed in the fruit of _Philadelphus speciosus_ by M. A. Gris, who observed that the so-called calyx-tube was provided with two small bracts, from the axil of one of which proceeded a small flower-bud.[177]

[Ill.u.s.tration: FIG. 93.--Small buds projecting from the edges of the fruit in _Opuntia_.]

The fruits of _Opuntia Salmiana_, _O. fragilis_,[178] _O. monacantha_, and of some species of _Echinocactus_, have been observed to form small fruit-like branches around their summits. M. Napoleon Doumet describes the fruit as ripening as usual, but as being dest.i.tute of seeds in the interior; after a little while the fruit begins to wither, and then a circle of small buds, like those of the stem, may be seen at the top of the fruit, each bud springing from the axil of a little tuft of wool and spines found on the fruit. These little buds elongate into long shoots, produce flowers the following year, which flowers exhibit the same peculiarity. Gasparini and Tenore are said to have recorded the same fact as long since as 1832. The specimen from which the figure (fig. 93) was taken produced its fruits in the Royal Gardens at Kew, and is now preserved in the museum of that establishment. The advent.i.tious growth in these cases appears to arise from the tufts of spines, which, it has been suggested, are the h.o.m.ologues of the sepals. There can, however, be little doubt that the outer and lower portion of the fruit of _Opuntia_ and its allies is a dilatation of the flower-stalk. This is borne out by the fruits of _Pereskia_, which bear leaves on their surface arranged spirally; indeed, the fruits of _Pereskia Bleo_ are mentioned as producing buds from their summits, in the same way as the _Opuntia_ just cited. _P. Bleo_ is said, by M. Delavaud,[179] to present this anomaly as a constant occurrence. On the summit of the primary fruit, arising apparently from the axils of the sepals, or of small leafy bracts in that situation, are a series of fruit-like branches, which, in their turn, are surmounted by others, even to the fourth generation.

The fruits of _Tetragonia expansa_ frequently have attached to their side a secondary flower or fruit in such a position as to lead to the inference that it springs from the upper portion of the peduncle which is dilated to invest the true carpels. In other instances it is due to an adhesion of the pedicel to the side of the fruit. In either case the production of an advent.i.tious bud might be considered as an ill.u.s.tration of prolification of the inflorescence, though not as was supposed by Moquin and others of axillary prolification.[180]

Buds have also been produced artificially on the surface of some of the fruits in the construction of which the axis is supposed to share; thus, the unripe fruits of some species of _Lecythis_ were stated by Von Martius, at a meeting of the German Naturalists at Carlsruhe, to produce buds when placed in the earth. The fruit of these plants is probably of the same nature as that of the _Pomaceae_, and Baillon[181] succeeded in producing buds on the surface of the inferior ovary of _Jussiaea_.

Some of the cases just mentioned have been considered to be instances of prolification of the fruit, but the fruit has little to do with the appearances in question.

=Formation of advent.i.tious flowers and fruits within the ovary.=--This generally arises either from subst.i.tution of a flower-bud for an ovule or from prolification; there are certain cases, however, where the new growth seems not to be either due to metamorphosis or to prolification strictly.

The cut, fig. 94, represents a case where, in the dilated upper portion of the ovary of _Sinapis arvensis_, two flower-buds were found projecting from a raised central line, corresponding, as it would seem, to the midrib, and not to the margins of the carpel. Similar cases have occurred in _Nasturtium amphibium_, _Bra.s.sica Rapa_, and _Pa.s.siflora quadrangularis_.

[Ill.u.s.tration: FIG. 94.--Distended pod of _Sinapis arvensis_ bearing in the interior stalked flower buds.]