FOOTNOTES:

Fig.98.—1. Vertical section of flower ofBæckea diosmæfolia, showing stamens within the ovary; magnified ten times. 2. Transverse section of ovary. 3. Stamen. 4. Imperfect stamen.

This case differs from most that have been recorded, and in which there has been a more or less complete substitution of anther for carpel, or where the tissues of the carpel have produced pollen, and so taken upon themselves the appearance and functions of anthers. Instances of this latter kind are not uncommon; but in theBæckeathere were perfect stamens proceedingfrom perfect and completely closed ovaries. Moquin-Tandon[183]cites from Agardh an instance which seems more closely to resemble the state of things in theBæckea, and which occurred in a double hyacinth, wherein both anthers and ovules were borne on the same placenta. Probably, though the fact is not stated, the ovary of the hyacinth was open; and we are told that the flower was double—that it was, in fact, modified and changed in more organs than one; while in theBæckeanothing at all unusual was observed till the ovary was cut open. The style was present even in those flowers where there was no axile placenta; hence in these cases it could not be, as Lindley stated it to be in the closely alliedBabingtonia, a prolongation of the placenta.[184]

Formation of pollen within the ovules.—This has now been recorded in two instances by Mr. S. J. A. Salter inPassiflora cæruleaand inP. palmata,[185]and by the author inRosa arvensis.[186]

Fig.99.—Pollen within the ovule ofPassiflora(after Salter).

In the case of the passion-flower there were various malformations in the ovaries, which were all more orless split open at the distal end, indicating a tendency towards dialysis. The pollen-bearing ovules were borne on the edges of these ovaries, and presented various intermediate conditions between anthers and ovules, commencing at the distal extremity of the carpel with a bi-lobed anther, and passing in series to the base of the ovary, an antheroid body of ovule-like form, a modified ovule containing pollen, an ovule departing from a perfectly natural condition only in the development of a few grains of pollen in its nucleus, and, finally, a perfect, normal ovule.

In the flowers of the Rose the stamens exhibited almost every conceivable gradation between their ordinary form and that of the carpels, while some of the ovules contained pollen in greater or less abundance. Speaking generally, the most common state of things in these flowers was the occurrence on the throat of the calyx, in the position ordinarily occupied by the stamens, and sometimes mingled with those organs, of twisted, ribbon-like filaments, which bore about the centre one or more pendulous, anatropous ovules on their margins. Immediately above the latter organs were the anther-lobes, more or less perfectly developed, and surmounting these a long style, terminating in a fringed, funnel-shaped stigma. Sometimes the ovules were perfect, at other times the nucleus protruded through the foramen, while in a third set the nucleus was included within the tegument, the ovules having in all respects their natural external conformation, containing, however, not only pollen-grains, but also a layer of those peculiar spheroidal cells, including a fibrous deposit, which are among the normal constituents of the anther. In one case, where the coat of the ovule was imperfect, and allowed the nucleus to protrude, the pollen was evidently contained within the central mass of the structure. In this instance the fibrous cells were not detected, these being only found in cases where the investment of the ovule was perfect; and hence it seems likely that the fibrous cells were part of the coatof the ovule, while the pollen was formed within the nucleus. In no case was any trace of embryo sac to be seen.

The main interest, as Mr. Salter remarks, in these cases is physiological; so far as structure alone is concerned, there does not appear any reason why pollen-grains should not be developed in any portion of the plant; the mother cells in which the pollen is formed not differing, to all outward appearance, from any other cells, unless it be in size.

The fundamental unity of construction in all the organs of plants could hardly be better illustrated than by these cases; while, in spite of their exceptional nature, they must be of great interest physiologically, as showing the wide limits of possible variation which thus may even involve the sex, "for an ovule to develop pollen within its interior," says Mr. Salter, "is equivalent to an ovum in an animal being converted into a capsule of spermatozoa. It is a conversion of germ into sperm, the most complete violation of individuality and unity of sex. * * * * The occurrence of an antheroid ovule and a normal ovule on the same carpellary leaf realises the simplest and the most absolute form of hermaphroditism."

It must, however, be remarked that the term substitution would be preferable to conversion. There is, at present, no evidence to show that the germinal vesicles were present in these cases; on the other hand, it seems most probable that they were not, so that the presence of the pollen-cells must be considered as simply adventitious. It can hardly be that they were, in the first instance, germinal vesicles, which, in course of time, became so modified as to assume the appearance of pollen-grains. Between the nucleus of the ovule and the tubercle of cellular tissue constituting the primordial anther, there is little or no difference, so that it may be said that, for a time, there is no distinction of sex in the nascent flower, but as development goes on, the difference becomes perceptible.It cannot at present be stated what precise circumstances induce the one mass to form mother-cells and pollen-grains, and the other to develop an embryo sac and germinal vesicles. Position and external circumstances may have some indirect effect, and it may, perhaps, be significant that in all the instances of polliniferous ovules, the ovular structures have been exposed on an open carpel or otherwise, in place of being confined within the cavity of a closed ovary, as under ordinary circumstances. Even among Conifers the ovuligerous scales are so closely packed that there is little or no exposure of the ovules. But, apart from all speculative notions as to the relation between the structure and functions of the anther and of the ovule respectively, and of the possibility or the reverse of parthenogenesis, it will clearly be necessary in any future alleged occurrence of the latter phenomenon to ascertain whether any or all of the apparent ovules are, or are not, anthers in disguise.

Homomorphic flowers of "Compositæ."—In a large section of theCompositæthere is, as is well known, a distinction between the florets of the "disc" and those of the "ray," the latter being ligulate, the former tubular.

In what are erroneously called double flowers in this order,e.g.in the Chrysanthemum, Dahlia, &c. &c., the florets are all ligulate. This change is sometimes classed with peloria, but there is no abnormal regularity in these cases. On the other hand, were the ligulate florets to be all replaced by tubular ones, the term peloria would be more strictly applicable. It will be remembered that in the sub-orderLigulifloræ, the florets are naturally all ligulate, so that the change above mentioned is not in itself a very grave one.

Heterotaxy affecting the inflorescence.—Under the head of Prolification, Heterogamy, &c., various deviations from the normal inflorescence are alluded to. In this place, therefore, it is only necessary to mention certain raredeviations from the customary arrangement of the inflorescence, such as the change from a definite centrifugal form of inflorescence to an indefinite centripetal one. This occurs occasionally in roses, where the shoot, instead of terminating in a flower-bud, lengthens and bears the flower-bud on its sides as in a raceme.

In the hyacinth, the inflorescence of which is properly indefinite, the terminal flower may frequently be found to expand first, though in order of development it may have been the last formed.

It occasionally happens that certain plants will, contrary to their usual custom, bloom twice in the same season; this usually arises from the premature development of buds which, under ordinary circumstances, would not unfold till the following spring. In these instances of what the French term "fleuraison anticipée," the position of inflorescence is not changed, but there are other cases where the position of the inflorescence is altered, as in the laburnum, where, in some seasons, racemes may be seen springing from short lateral "spurs" along the sides of the branches, as well as from the extremities of long shoots.

Of a similar nature are those cases wherein stems or branches usually sterile become fertile; this happens inEquisetaceæ,[187]inRestiaceæ, and other orders. In the equisetums, the condition in question has been specially noticed to occur after prolonged drought.

Equisetaceæare likewise subject to an anomaly called by Duval Jouve interruption of the spike, and wherein the scales bearing the spore cases are separated by whorls of branches instead of forming one compact unbroken spike as usual.

This alternation of the organs of vegetation and reproduction may also be seen occasionally inTypha, and other plants.

Kirschleger describes a case in which the male catkins ofSalix cinereawere placed at the ends of thebranches instead of being lateral productions; moreover the usual articulation was not formed, so that the catkin was persistent instead of deciduous.[188]

Supra-soriferous ferns.—In the great majority of ferns the sori or clusters of spore cases are placed on the under surface of the fronds; nevertheless, a few cases are on record where the fructification is produced on the upper as well as on the lower surface, and sometimes abundantly so. This occasionally happens from the elongation of the normally placed sorus, which thus extends to the margin, and returns on the upper side, when the sori chance to be placed opposite to the marginal crenatures. But it is also frequently the case that the sori are produced on the upper side, distinctly within the margin, and where there are no corresponding sori beneath. Those varieties which have the margin crenated or lobed seem most liable to assume this abnormal supra-soriferous condition. Among the ferns in which this condition has been observed are the following:Scolopendrium vulgare,Polypodium anomalum, Hook.,Asplenium Trichomanes,Cionidium Moorei.[189]

FOOTNOTES:[147]'Gard. Chron.' 1852, p. 51.[148]'Flora.' 1858, pp. 32–42.[149]'Journ. Linn. Soc.,' vol. vi; "Botany," 1862, p. 24.[150]'Tijdschrift voor Natuur. Geschied,' 1836, vol. iii, tab. vii, p. 171.[151]Rœper, 'Enum. Euphorb.,' p. 19. Bernhardi, 'Linnæa,' vii, p. 561, tab. xiv, f. 1. Wydler, "Subcotyled. sprossbildung," 'Flora,' 1850, p. 337. Hooker, 'Trans. Linn. Soc.,' vol. xxiv, p. 20 (Welwitschia).[152]'Misc. Austriac. ad Bot.,' vol. i, p. 133, t. 5.[153]See also Carrière, 'Revue Horticole,' 1866, p. 442; and as to pears, Radlkofer in 'Bericht über die Thätigkert der Baierischen Gartenbau Gesellschaft,' 1862, p. 74, t. i.[154]'Flora Indica,' p. 23.[155]'Bull. Soc. Bot. Fr.,' 1856, p. 53.[156]'Trans. Linn. Soc.' xxvi, p. 142, tab. iv,B.[157]"Si arbusculam, quæ in ollâ antea posita, quotannis floruit et fructus protulit, deinde deponamus in uberiori terra calidi caldarii, proferet illa per plures annos multos ac frondosos ramos, sine ullo fructu. Id quod argumento est, folia inde crescere, unde prius enati sunt flores; quemadmodum vicissim, quod in folia nunc succrescit, id, naturâ ita moderante, in flores mutatur, si eadem arbor iterum in ollâ seritur."—Linnæus, 'Prolepsis,' § iii.[158]'Rev. Hortic.' May, 1868, 'Gardeners' Chronicle,' 1868, pp. 572, 737.[159]Cited in 'Annals Nat. Hist.,' 1845, vol. xv, p. 177.[160]'Ann. Scienc. Nat.,' vol. xiv, 1860, p. 13.[161]Naudin, 'Ann. Sc. Nat.,' 2nd ser., 1840, vol. xiv, p. 14, fig. 6, pl. i (Drosera). St. Hilaire, 'Comptes Rendus,' ix, p. 437.[162]Hance, 'Hook. Journ. Botany,' 1849, vol. i, p. 141, pl. v.[163]Booth, 'Gard. Chron.,' Jan. 1st, 1853, p. 4.[164]Lindley, 'Theory of Horticulture,' ed. 2, p. 273.[165]'Hook. Journ. of Botany,' 1852, iv, p. 206. See also the curiousBegonia gemmipara, 'Hook. fil. Illust. Himal. Plant.,' t. xiv.[166]'Phytanth.,' n. 36,d.[167]'Ann. Scienc. Nat.,' 3rd series. 1853. vol. xix, p. 251, tab. 14.[168]Carrière, 'Revue Horticole.' 1868, p. 184.[169]'Gard. Chron.,' 1858, p. 556.[170]1863, p. 556, &c.[171]'Ann. Nat. Hist.,' 1845, vol. xvi, p. 355.[172]See also Lindley, 'Veg. Kingd.,' p. 109 et 116a, where the views of Raspail, R. Brown, Mohl, Henslow, and others, are discussed.[173]It has been observed that if a plant is supplied with copious nourishment the flowering-period is delayed; but that moderate or even scanty nourishment accelerates it. Goethe, 'Metam.,' § 30. See also Wolff, 'Theoria Generationis,' 1759; Linn. 'Prolepsis,' §§ 3 and 10.[174]Moquin-Tandon, p. 384; also Lindl., 'Elements of Botany,' p. 65, fig. 130; "Theory of Horticulture," p. 86. 'Gard. Chron.,' 1851, p. 723; Irmish, 'Flora,' 1858, p. 38, &c.[175]Caspary, 'Bull. Soc. Bot. Fr.,' vol. vi, 1859, p. 235; also Payer, ibid., vol. i, 1854. p. 283.[176]Trécul, 'Ann. Sc. Nat.,' 2nd ser., vol. xx, p. 339.[177]'Bull. Soc. Bot. Fr.,' vol. vii, 1858, p. 331.[178]'Bull. Soc. Bot. Fr.,' vol. i. p. 306, vol. v, p. 115. 'Illustr. Hortic.,' xii, 1865, Misc. 79. 'Rev. Horticole,' 1860 p. 204, et 1867 p. 43.[179]'Bull. Soc. Bot. Fr.,' 1858, p. 685.[180]The structure of this flower is discussed at some length in a paper by the author on axillary prolification. 'Trans. Linn. Soc.,' vol. xxiii, p. 486, t. liv. fig. 3. See also 'Clos. Bull. Soc. Bot. Fr.,' vol. v, 1855, p. 672. Seringe et Heyland, 'Bull. Bot.,' i, p. 8. 'Pallas Enum. Plant. Hort. Demidoff,' append, c, ic.[181]'Adansonia,' i, 181.[182]'Adansonia.' vol. iii, p. 351, tab. xii.[183]'Elém. Térat. Végét.,' p, 218.[184]Masters, 'Journ. Linn. Soc.,' vol. ix, 1866, p. 334.[185]'Trans. Linn. Soc.,' vol. xxiv, p. 143. tab. xxiv.[186]'Brit. Assoc. Report,' Dundee, 1867; and Seemann's 'Journal of Botany,' 1867, p. 319, tab. lxxii, figs.B1–9.[187]Duval Jouve, 'Hist. Equiset. France.' 1864, p. 154.[188]'Flora,' t. xxiv, 1841, p. 340.[189]Moore, 'Nature-Printed British Ferns,' 8vo edition, vol. ii. p. 135. tab. lxxxv,B, &c.

[147]'Gard. Chron.' 1852, p. 51.

[148]'Flora.' 1858, pp. 32–42.

[149]'Journ. Linn. Soc.,' vol. vi; "Botany," 1862, p. 24.

[150]'Tijdschrift voor Natuur. Geschied,' 1836, vol. iii, tab. vii, p. 171.

[151]Rœper, 'Enum. Euphorb.,' p. 19. Bernhardi, 'Linnæa,' vii, p. 561, tab. xiv, f. 1. Wydler, "Subcotyled. sprossbildung," 'Flora,' 1850, p. 337. Hooker, 'Trans. Linn. Soc.,' vol. xxiv, p. 20 (Welwitschia).

[152]'Misc. Austriac. ad Bot.,' vol. i, p. 133, t. 5.

[153]See also Carrière, 'Revue Horticole,' 1866, p. 442; and as to pears, Radlkofer in 'Bericht über die Thätigkert der Baierischen Gartenbau Gesellschaft,' 1862, p. 74, t. i.

[154]'Flora Indica,' p. 23.

[155]'Bull. Soc. Bot. Fr.,' 1856, p. 53.

[156]'Trans. Linn. Soc.' xxvi, p. 142, tab. iv,B.

[157]"Si arbusculam, quæ in ollâ antea posita, quotannis floruit et fructus protulit, deinde deponamus in uberiori terra calidi caldarii, proferet illa per plures annos multos ac frondosos ramos, sine ullo fructu. Id quod argumento est, folia inde crescere, unde prius enati sunt flores; quemadmodum vicissim, quod in folia nunc succrescit, id, naturâ ita moderante, in flores mutatur, si eadem arbor iterum in ollâ seritur."—Linnæus, 'Prolepsis,' § iii.

[158]'Rev. Hortic.' May, 1868, 'Gardeners' Chronicle,' 1868, pp. 572, 737.

[159]Cited in 'Annals Nat. Hist.,' 1845, vol. xv, p. 177.

[160]'Ann. Scienc. Nat.,' vol. xiv, 1860, p. 13.

[161]Naudin, 'Ann. Sc. Nat.,' 2nd ser., 1840, vol. xiv, p. 14, fig. 6, pl. i (Drosera). St. Hilaire, 'Comptes Rendus,' ix, p. 437.

[162]Hance, 'Hook. Journ. Botany,' 1849, vol. i, p. 141, pl. v.

[163]Booth, 'Gard. Chron.,' Jan. 1st, 1853, p. 4.

[164]Lindley, 'Theory of Horticulture,' ed. 2, p. 273.

[165]'Hook. Journ. of Botany,' 1852, iv, p. 206. See also the curiousBegonia gemmipara, 'Hook. fil. Illust. Himal. Plant.,' t. xiv.

[166]'Phytanth.,' n. 36,d.

[167]'Ann. Scienc. Nat.,' 3rd series. 1853. vol. xix, p. 251, tab. 14.

[168]Carrière, 'Revue Horticole.' 1868, p. 184.

[169]'Gard. Chron.,' 1858, p. 556.

[170]1863, p. 556, &c.

[171]'Ann. Nat. Hist.,' 1845, vol. xvi, p. 355.

[172]See also Lindley, 'Veg. Kingd.,' p. 109 et 116a, where the views of Raspail, R. Brown, Mohl, Henslow, and others, are discussed.

[173]It has been observed that if a plant is supplied with copious nourishment the flowering-period is delayed; but that moderate or even scanty nourishment accelerates it. Goethe, 'Metam.,' § 30. See also Wolff, 'Theoria Generationis,' 1759; Linn. 'Prolepsis,' §§ 3 and 10.

[174]Moquin-Tandon, p. 384; also Lindl., 'Elements of Botany,' p. 65, fig. 130; "Theory of Horticulture," p. 86. 'Gard. Chron.,' 1851, p. 723; Irmish, 'Flora,' 1858, p. 38, &c.

[175]Caspary, 'Bull. Soc. Bot. Fr.,' vol. vi, 1859, p. 235; also Payer, ibid., vol. i, 1854. p. 283.

[176]Trécul, 'Ann. Sc. Nat.,' 2nd ser., vol. xx, p. 339.

[177]'Bull. Soc. Bot. Fr.,' vol. vii, 1858, p. 331.

[178]'Bull. Soc. Bot. Fr.,' vol. i. p. 306, vol. v, p. 115. 'Illustr. Hortic.,' xii, 1865, Misc. 79. 'Rev. Horticole,' 1860 p. 204, et 1867 p. 43.

[179]'Bull. Soc. Bot. Fr.,' 1858, p. 685.

[180]The structure of this flower is discussed at some length in a paper by the author on axillary prolification. 'Trans. Linn. Soc.,' vol. xxiii, p. 486, t. liv. fig. 3. See also 'Clos. Bull. Soc. Bot. Fr.,' vol. v, 1855, p. 672. Seringe et Heyland, 'Bull. Bot.,' i, p. 8. 'Pallas Enum. Plant. Hort. Demidoff,' append, c, ic.

[181]'Adansonia,' i, 181.

[182]'Adansonia.' vol. iii, p. 351, tab. xii.

[183]'Elém. Térat. Végét.,' p, 218.

[184]Masters, 'Journ. Linn. Soc.,' vol. ix, 1866, p. 334.

[185]'Trans. Linn. Soc.,' vol. xxiv, p. 143. tab. xxiv.

[186]'Brit. Assoc. Report,' Dundee, 1867; and Seemann's 'Journal of Botany,' 1867, p. 319, tab. lxxii, figs.B1–9.

[187]Duval Jouve, 'Hist. Equiset. France.' 1864, p. 154.

[188]'Flora,' t. xxiv, 1841, p. 340.

[189]Moore, 'Nature-Printed British Ferns,' 8vo edition, vol. ii. p. 135. tab. lxxxv,B, &c.

This term is here intended to apply to all those cases in which the arrangement of the sexual organs is different from what it is habitually. It is evident that in many instances there is no malformation, no monstrosity, but rather a restoration of organs habituallysuppressed, a tendency towards structural completeness rather than the reverse. It must be also understood that the following remarks apply to structural points only, and are not intended to include the question of function. The occurrence of heteromorphic unions renders it necessary to keep in mind that plants hermaphrodite as to structure are by no means necessarily so as to function.

The simplest case of this alteration in the relative position of the sexes is that which occurs in monœcious plants, where the male and female flowers have a definite position, but which in exceptional instances is altered.

Change in the relative position of male and female flowersmay thus occur in any monœcious plant. Cultivated maize,Zea Mays, frequently exhibits alterations of this kind; under ordinary circumstances, the male inflorescence is a compound spike, occupying the extremity of the stem, while the female flowers are borne in simple spikes at a lower level, but specimens may now and then be found where the sexes are mixed in the same inflorescence; the upper branching panicle usually containing male flowers only, under these circumstances, bears female flowers also.[190]In like manner, but less frequently, the female inflorescence occasionally produces male flowers as well.

Among the species ofCarexit is a common thing for the terminal spike to consist of male flowers at the top, and female flowers at the base; the converse of this, where the female flowers are at the summit of the spike, is much more uncommon. An illustration of this occurrence is given in the figure (fig. 100). Among theConiferænumerous instances have been recorded of the presence of male and female flowers on the same spike, thus Mr. now Professor Alexander Dickson exhibited at the Botanical Society of Edinburghin July, 1860, some malformed cones ofAbies excelsa, in which the inferior part of the axis was covered with stamens, whilst the terminal portion produced bracts and scales like an ordinary female cone. The stamens of the lower division were serially continuous with the bracts above. Some of the lower scales of the female portion were in the axils of the uppermost stamens, which last were somewhat modified, the anther cells being diminished, whilst the scale-like crest had become more elongated and pointed, in fact, more or less resembling the ordinary bracts.[191]Mohl, Schleiden, and A. Braun have observed similar cones inPinus alba, and Cramer figures and describes androgynous cones inLarix microcarpa. C. A. Meyer ('Bull. Phys. Math.,' t. x, 1850) also describes some catkins ofAlnus fruticosawhich bore male flowers at the top, and female flowers at the base.

Fig.100.—Spike ofCarex acuta, with female flowers at the summit.

On the subject of this section the reader may consult A. Braun,. 'Das Individ.,' 1853, p. 65. Caspary, 'De Abietin. flor. fem. struct. morphol.' Schleiden. 'Principles,' English edition, p. 299. Mohl, 'Verm. Schrift.,' p. 45. Meyen in 'Wiegm. Archiv.,' 1838, p. 155. Cramer, 'Bildungsabweich,' p. 4, tab. v, figs. 13–17. Parlatore, 'Ann. Sc. Nat.,' ser. iv, vol. xvi, p. 215, tab. 13a. See also under the head of Prolification, Substitutions, &c.

Change from the monœcious to the diœcious condition.—This is of less frequent occurrence than might have been anticipated. In the 'Gardeners' Chronicle,' 1847, pp. 541 and 558, several instances are noted of walnut trees bearing female flowers to the exclusion of males. The mulberry tree has also been noticed to produce female blossoms only, while in other plants male flowers only are developed.

It seems probable that the age of the plant may have something to do with this production of flowers of one sex to the exclusion of the other.

Change from the diœcious to the monœcious condition.—Androgynism.—This is of far more common occurrence than the preceding.

Fig.101.—Monœcious inflorescence of Hop.

In the hop (Humulus Lupulus), when monœcious, the female catkins are usually borne on the ends of the branches as shown in the cut (fig. 101), and a similarthing has been noticed inUrtica dioicaby Clos, 'Bull. Soc. Bot. France,' vol. 9, p. 7.

Baillon ('Etudes du groupe des Euphorbiacées,' p. 205) mentions the following species of that order as having been seen by him with monœcious inflorescence:Schismatopera distichophylla,Mozinna peltata,Hermesia castaneifolia. Oliver mentions ('Hook. Icon. Plant.,' t. 1044) that inLeitneria floridanathe upper scales of the male catkin occasionally subtend an ovary.

It would seem that external conditions have some effect in determining the formation of one sex, as in some species ofCarex, while in the case ofSalix repens, Hampe[192]says that when grown partially or for a time under water, those twigs which are thrust up above the surface bear female flowers, while those twigs that blossom after the water is dried up, produce male flowers only.

Carrière[193]says that a plant ofStauntonia latifoliawhich for some years produced stamens only, now produces flowers of both sexes; it was diœcious, but is now monœcious. The same author alludes to a similar occurrence inJuniperus Virginiana. Thehopsis also said to vary in sexual characteristics from time to time.[194]In addition to the genera, already named, in which this production of flowers of both sexes has been observed may be mentionedTaxus! Gunnera! Urtica! Mercurialis! Restio! Cannabis! Salix! Humulus!as well as others in which the change is less frequent.

Among cryptogams a similar change occurs. As an illustration may be citedLeucobryum giganteum, as quoted from Müller in Henfrey's 'Botanical Gazette,' i, p. 100.

As to androgynous willows, in addition to the references given under the head of Substitution of stamens for pistils, see Schlechtendal, 'FloraBerol.,' ii. p. 259. Tausch, 'Bot. Zeit.,' 1833, i. p. 229. Koch, 'Synops. Flor. Germ.,' 740. Host, 'Flor. Aust,.' ii, p. 641 (S. mirabilis). See also Hegelmaier, 'Württemberg Naturwissenshaft Jahreshefte,' 1866, p. 30. Other references to less accessible works are given in 'Linnæa,' xiv, p. 372.

Change from hermaphroditism to unisexuality.—Many flowers ordinarily hermaphrodite as to structure, become unisexual by the abortion or suppression of their stamens, or of their carpels, as the case may be. This phenomenon is lessened in interest since the demonstration of the fact by Darwin and others, that many plants, structurally hermaphrodite, require for the full and perfect performance of their functions the cooperation of the stamens and pistils, belonging to different individuals of the same species.

Some of theRanunculaceæconstantly exhibit a tendency towards the diœcious condition, and the rarity with which perfect seeds ofRanunculus Ficariaare formed is to be attributed, in great measure, to the deficiency of pollen in the anthers of these flowers.Ranunculus auricomusalso is frequently sterile. Specimens ofRanunculus bulbosusmay be met with in which every flower is furnished with carpels, most of which have evidently been fertilised, although there are no perfect stamens in the flowers.

Knight and other vegetable physiologists have been of opinion that a high temperature favours the production of stamens, while a lower degree of heat is considered more favorable to the production of pistils, and in this way the occurrence of "blind" strawberries has been accounted for. Mr. R. Thompson, writing on this subject, speaks of a plantation of Hautbois strawberries which in one season were wholly sterile, and accounts for the circumstance as follows: the plants were taken from the bearing beds the year previous, and were planted in a rich well-manured border, in which they started rapidly into too great luxuriance, the growth being to leaves rather than to fruit. The following season these same plants borea most abundant crop, hence these plants were accidentally prevented from perfecting their female organs.[195]

Mr. Darwin[196]cites from various sources the following details relating to strawberries which it may be useful to insert in this place, as throwing some light upon the production of unisexual flowers. "Several English varieties, which in this country are free from any such tendency, when cultivated in rich soils under the climate of North America commonly produce plants with separate sexes. Thus, a whole acre of Keen's seedlings in the United States has been observed to be almost sterile in the absence of male flowers; but the more general rule is, that the male plants over-run the females.... The most successful cultivators in Ohio plant, for every seven rows of pistillate flowers, one row of hermaphrodites, which afford pollen for both kinds; but the hermaphrodites, owing to their expenditure in the production of pollen, bear less fruit than the female plants."

Stratiotes aloideshas been said to produce its carpels with greater abundance towards the northern limits of its geographical distribution, and its stamens, on the other hand, are stated to be more frequently developed in more southern districts.

Honckenya peploidesaffords another illustration of the sexual arrangements in the flower being altered as it would seem by climatal conditions. Thus, in the United States, according to Professor Asa Gray, the flowers are frequently hermaphrodite, while in this country they are usually sub-diœcious.[197]

Treviranus[198]says that the flowers ofHippurisandCallitricheare apt to be hermaphrodite in summer, but female only at a later period.

For further remarks on this subject, see sections relating to suppression of stamens and pistils.

Change from unisexuality to hermaphroditism.—This occurrence depends on one of two causes, either organs are developed (stamens or pistils as the case may be), which are habitually absent in the particular flower; or some of the stamens may be more or less completely converted into or replaced by pistils, orvice versâ.

The first condition is the opposite of suppression; it is, as it were, a restoration of symmetry, and might be included under the head of regular peloria, inasmuch as certain organs which habitually undergo suppression at a certain stage in their development, by exception, go on growing, and produce a perfect, instead of an imperfect flower. In teratological records it is not always stated clearly to which of the two above-named causes the unusual hermaphroditism belongs, though it is generally easy to ascertain this point. Very many, perhaps all, diclinous flowers may, under certain conditions, become perfect, at least structurally. I have myself seen hermaphrodite flowers inCucurbita,[199]Mercurialis,Cannabis,Zea Mays, andAucuba japonica, as well as in manyRestiaceæ, notablyCannamois virgataandLepyrodia hermaphrodita.Spinacia oleracea,Rhodiola rosea,Cachrys taurica, andEmpetrum nigrumare also occasionally hermaphrodite.

Gubler[200]alludes to a similar occurrence inPistacia Lentiscus, wherein, however, he adds that there was a deficiency of pollen in the flowers.

Schnizlein[201]observed hermaphrodite flowers in the beech,Fagus sylvatica, the ovaries being smaller than usual, and the stamens epigynous.

Baillon[202]enumerates the followingEuphorbiaceæas having exceptionally produced hermaphrodite flowers,Crozophora tinctoria,Suregadasp.,Phyllanthus longifolius,Breyniasp.,Philyra brasiliensis,Ricinus communis,Conceveiba macrophylla,Cluytia semperflorens,Wall, nonRoxb.Mercurialis annuaandCleistanthus polystachyus.

In some of these cases the hermaphroditism is due to the development of anthers on the usually barren staminodes, though, in other cases, the stamens would seem to be separate, independent formations, as they do not occupy the same relative position that the ordinary stamens would do if developed.[203]

Fig. 102.—Flower ofFuchsiain which the calyx was leafy, the petals normal (reflexed in the figure), the stamens partially converted into ovaries, the ordinary inferior ovary being absent. See Substitution.

Robert Brown[204]observed stamens within the utricle ofCarex acuta, and Gay is stated by Moquin ('El. Ter.Veg.,' p. 343) to have observed a similar occurrence inCarex glauca.

Paasch[205]observed a similar occurrence inC. cæspitosa, and Schauer, inC. paludosa,[206]though in the latter instance the case seems to have been one of transformation or substitution rather than one of hermaphroditism.

The second cause of this pseudo-hermaphroditism is due either to the more or less perfect mutation of male and female organs, or it may be to the complete absence of one and its replacement by another, as when out of many stamens, one or more are deficient, and their places occupied by carpels. This happens very frequently in willows and poplars, and has been seen in the beech.[207]

Fig. 103.—Hermaphrodite flower ofCarica Papaya.

InBegonia frigida[208]the anomaly is increased by the position of the ovaries above, the perianth, a position due, not to any solution or detachment of the latter from the former, but simply to the presence of ovaries where, under ordinary circumstances, stamens only areformed, as happened also in a garden variety of aFuchsia, wherein, however, the change was less perfect than in theBegonia, and in which, as the flower is naturally hermaphrodite, the alteration is of the less importance.

Fig.104.—Ovuliferous anthers—Cucurbita.

In hermaphrodite flowers ofCarica Papaya(fig. 103) there is a single row of five stamens instead of two rows of five each as in the normal male flowers, the position of the second or inner row of stamens being occupied by five carpels, which, however, are not adherent to the corolla as the stamens are, thus, supposing thearrangement of parts in the normal male flowers to be as follows:

---------------------------S S S S S---------------------------| p p p p p|| st st st st st|| st st st st st|

That of the hermaphrodite blossoms would be, in brief, as follows:

| 5 S|------------| 5 p|| 5 st|| 5 c|

One of the most curious cases of this kind recorded is one mentioned by Mr. Berkeley,[209]wherein a large white-seeded gourd presented a majority of flowers in which the pollen was replaced by ovules. It would seem probable from the appearances presented by the figure that these ovules were, some of them, polliniferous, like those of thePassiflora, &c., described at p. 185, but nothing is stated on the subject.

See also section on Regular Peloria, Substitution, Pistillody of the stamens, &c.

FOOTNOTES:[190]See also Clos., 'Mem. Acad. Toulouse,' sixth ser., t. iii, pp. 294–305. Scott, 'Trans. Bot. Soc. Edinburgh,' t. viii, p. 60. Wigand, 'Flora,' 1856, p. 707.[191]Professor Dickson concludes from the examination of these structures that the male cone, consisting of simple stamens developed on one common axis, must be regarded as a simple male flower, while the axillary scales of the female cone are by him compared with the flattened shoots ofRuscus.[192]'Linnæa,' xiv, 367.[193]Rev. Hortic.,' January, 1867.[194]See Royle, 'Man. Materia Medica,' ed. 1, p. 567.[195]Thomson, 'Gardener's Assistant,' p. 577.[196]'Variation of Animals and Plants,' i, 353.[197]Babington, 'Ann. Nat. Hist.,' vol. ix, 1852, p. 156.[198]'Phys. der Gewächse,' ii, p. 323.[199]See also Schlechtendal, 'Linnæa,' viii, p. 623, and Lindley, 'Veg. Kingd.,' p. 315.[200]'Bull. Soc. Bot. France,' vol. ix, p. 81.[201]Cited in Henfrey, 'Bot. Gazette.' 3, p. 11.[202]Baillon. 'Etudes du Groupe des Euphorbiacées,' p. 205, tab. xv, fig. 19, tab. xix, fig. 31.[203]See also Guillemin, 'Mém. Soc. Nat. Hist. Paris,' I, p. 16; hermaphrodite flowers inEuphorbia esula.[204]'Prod. Flor. N. Holl.,' p. 242.[205]'Bot. Zeit.,' 1837, p. 335.[206]'Pflanz, Terat.,' von Moquin-Tandon, p. 208.[207]Schnizlein, loc. cit.[208]'Bot. Mag.,' tab. 5160, fig. 4. See also 'Gard. Chron.,' 1860, pp. 146, 170; 1861, p. 1092.[209]'Gard. Chron.,' 1851, p. 499.

[190]See also Clos., 'Mem. Acad. Toulouse,' sixth ser., t. iii, pp. 294–305. Scott, 'Trans. Bot. Soc. Edinburgh,' t. viii, p. 60. Wigand, 'Flora,' 1856, p. 707.

[191]Professor Dickson concludes from the examination of these structures that the male cone, consisting of simple stamens developed on one common axis, must be regarded as a simple male flower, while the axillary scales of the female cone are by him compared with the flattened shoots ofRuscus.

[192]'Linnæa,' xiv, 367.

[193]Rev. Hortic.,' January, 1867.

[194]See Royle, 'Man. Materia Medica,' ed. 1, p. 567.

[195]Thomson, 'Gardener's Assistant,' p. 577.

[196]'Variation of Animals and Plants,' i, 353.

[197]Babington, 'Ann. Nat. Hist.,' vol. ix, 1852, p. 156.

[198]'Phys. der Gewächse,' ii, p. 323.

[199]See also Schlechtendal, 'Linnæa,' viii, p. 623, and Lindley, 'Veg. Kingd.,' p. 315.

[200]'Bull. Soc. Bot. France,' vol. ix, p. 81.

[201]Cited in Henfrey, 'Bot. Gazette.' 3, p. 11.

[202]Baillon. 'Etudes du Groupe des Euphorbiacées,' p. 205, tab. xv, fig. 19, tab. xix, fig. 31.

[203]See also Guillemin, 'Mém. Soc. Nat. Hist. Paris,' I, p. 16; hermaphrodite flowers inEuphorbia esula.

[204]'Prod. Flor. N. Holl.,' p. 242.

[205]'Bot. Zeit.,' 1837, p. 335.

[206]'Pflanz, Terat.,' von Moquin-Tandon, p. 208.

[207]Schnizlein, loc. cit.

[208]'Bot. Mag.,' tab. 5160, fig. 4. See also 'Gard. Chron.,' 1860, pp. 146, 170; 1861, p. 1092.

[209]'Gard. Chron.,' 1851, p. 499.

The deviations from the ordinary direction of organs partake for the most part more of the nature of variations than of absolute malposition or displacement. It must also be borne in mind how frequently the direction of the leaves, or of the flower, varies according to thestage of development which it has arrived at, to unequal or disproportionate growth of some parts, or to the presence of some impediment either accidental or resulting from the natural growth of the plant. These and other causes tend to alter the direction of parts very materially.

Change in the direction of axile organs, roots, stems, &c.—The roots frequently exhibit good illustrations of the effect of the causes above mentioned in altering the natural direction. The roots are put out of their course by meeting with any obstacle in their way. Almost the only exception to the rule in accordance with which roots descend under natural circumstances, is that furnished byTrapa natans, the roots of which in germination are directed upwards towards the surface of the water. So inSechium edule, the seed of which germinates while still in the fruit, the roots are necessarily, owing to the inverted position of the embryo, directed upwards in the first instance.

A downward direction of the stem or branches occurs in many weak-stemmed plants growing upon rocks or walls, or in trees with very long slender branches as inSalix Babylonica, and the condition may often be produced artificially as in the weeping ash.

The opposite change occurs in what are termed fastigiate varieties, where the branches, in place of assuming more or less of a horizontal direction, become erect and nearly parallel with the main stem as in the Lombardy poplar, which is supposed to be merely a form of the black Italian poplar.

M. de Selys-Longchamps has described a similar occurrence in another species of Poplar (P. virginianaDesf.), and amongst a number of seedling plants fastigiate varieties may frequently be found, which may be perpetuated by cuttings or grafts, or sometimes even by seed; hence the origin of fastigiate varieties of elms, oaks, thorns,chestnuts, and other plants which may be met with in the nurseries.

Sometimes when the top of the main stem is destroyed by disease or accident, one of the heretofore lateral shoots takes its place, and continues the development of the tree in the original direction. It is often an object with the gardener to restore the symmetry of an injured tree so that its beauty may ultimately not be impaired.[210]

Climate appears sometimes to have some influenceon the direction of branches, thus Dr. Falconer, as quoted by Darwin,[211]relates that in the hotter parts of India "the English Ribston-pippin apple, a Himalayan oak, a Prunus and a Pyrus all assume a fastigiate or pyramidal habit, and this fact is the more interesting as a Chinese tropical species ofPyrusnaturally has this habit of growth. Nevertheless many of the fastigiate varieties seen in gardens have originated in this country by variation of seeds or buds."

M. Carrière has also recorded a curious circumstance with reference to the fastigiate variety of the false acaciaRobinia pseudacacia; he states that if a cutting or a graft be taken from the upper portion of the tree, the fastigiate habit will be reproduced, and the branches will be furrowed and covered with short prickles; but if the plant be multiplied by detaching portions of the root-stock, then instead of getting a pyramidal tree with erect branches, a spreading bushy shrub is produced, with more or less horizontal, cylindrical branches, destitute of prickles.[212]

Eversion of the axis.—In the case of the fig, the peculiar inflorescence is usually explained on the supposition that the termination of the axis becomes concave, during growth, bearing the true flowers in the hollow thus formed. The cavity in this case would probably be due not to any real process of excavation, but to a disproportionate growth of the outer as contrasted with the central parts of the fig. Some species ofSempervivumhave a similar mode of growth, so that ultimately a kind of tube is formed, lined by the leaves, the central and innermost being the youngest. The hip of the Rose may be explained in a similar manner by the greater proportionate growth of the outer as contrasted with the central portions of the apex of the flower-stalk. In cases of median prolification, already referred to, the process is reversed, the central portionsthen elongate into a shoot and no cavity is formed. A fig observed by Zuccarini (figs. 105, 106) appears to have been formed in a similar manner, the flower-bearing summit of the stalk not being contracted as usual, the flowers projected beyond the orifice of the fig. If this view be correct the case would be one rather of lengthening of the axis than of absolute eversion since it was never inverted.

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