letter V. Such divergence is of frequent occurrence where fruits are

united by their stalks, because, as growth goes on, the tendency must necessarily be towards separation and divergence of the tips of the fruit.

In some cases of Syncarpy the fusion and interpenetration of the carpels is carried to such an extent that it is very difficult to trace on the outer surface the lines of union. The fruit in these cases resembles a single one of much larger size than usual. Moquin mentions a double apple in which the connection was so close that the fruit was not very different in form from what is customary, and a similar thing happens with the tomato. In the case of stone-fruits it sometimes happens, not only that the outer portions are adherent, but that the stones are so likewise.

M. Roeper has observed two apples grafted together, one of which had its stalk broken, and seemed evidently borne and nourished by the other apple;[51] and a similar occurrence happens not infrequently in the cucumber. Moquin has seen three united cherries having only a single stalk jointed to the central fruit, the lateral cherries having each a slight depression or cicatrix marking the situation of the suppressed stalks. Schlotterbec has figured three apples presenting precisely similar appearances.[52]

Fusion of two or more nuts (_Corylus_) is not uncommon; I have seen as many as five so united.[53] In these cases the fruits may be united together in a ring or in linear series.

In some _Leguminosæ_, contrary to the general rule in the order, more than one carpel is found; thus peas, French beans, and other similar plants, are occasionally met with having two or more pods within the same calyx, and in _Gleditschia triacanthos_ and _Cæsalpinia digyna_ this is so commonly the case as to be considered almost the normal state. (De Cand. 'Mem. Leg.,' pl. 2, fig. 6; pl. 3, fig. 2.) At times these carpels become fused together, and it becomes difficult, when the traces of the flower have disappeared, to ascertain whether these carpels were formed in one flower, or whether they were the result of the fusion of several blossoms. I have seen an instance of this kind in a plum in which there were two carpels in the same flower, the one being partially fused to the other. The nature of such cases may usually be determined by an inspection of the peduncle which shows no traces of fusion. (See chapter on Multiplication.)

When, however, the fruits are sessile, and they become grafted together, the kind of syncarpy is difficult to distinguish. It, may, nevertheless, be said as a general rule that the union brought about by the approximation of two fruits, after the fall of the floral whorls, is never so complete or so intimate as that determined by synanthy; and also that in those cases where there are supernumerary carpels in the flower, and those carpels become united together, they are rarely so completely fused that their individuality is lost.

An analogous phenomenon takes place not uncommonly in mosses, the spore capsules of which become united together in various ways and degrees. Schimper[54] cites the following species as subject to this anomaly:--_Buxbaumia indusiata_, _Leskea sericea_, _Hypnum lutescens_, _Anomodon alternatus_, _Clinacium dendroides_, _Bryum cæspititium_, _Brachythecium plumosum_, _Mnium serratum_, _Splachnum vasculosum_. It has also been observed in _Trichostomum rigidulum_ and _Hypnum triquetrum_.

In addition to the authorities already mentioned, the reader may consult Moquin-Tandon, 'El. Ter. Veg.,' p. 270. Turpin. 'Mém. greffe. Ann. Sc. Nat.,' ser. i, t. xxiv, p. 334. De Candolle, 'Organ. Veget.,' t. i. Duhamel, 'Phys. des Arbres,' t. i, p. 304, tab. xiii, xiv. Weber. 'Verhandl. Nat. Hist. Vereina f. d. Preuss. Rheinl. u. Westphal.,' 1860, p. 332, tab. vi. et vii.

=Synspermy, or Union of the Seeds.=--Seeds may be united together in various degrees, either by their integuments,[55] or by their inner parts. Such union of the seeds, however, is of rare occurrence. It takes place normally, to a slight extent, in certain cultivated forms of cotton, wherein the seeds are aggregated together into a reniform mass, whence the term kidney cotton. Union of the parts of the embryo is treated under another head (see Synophty).

=Adhesion between the axes of different plants.=--Under this head may be classed the union that takes place between the stems, branches, or roots of different plants of the same species, and that which occurs between individuals of different species; the first is not very different in its nature from cohesion of the branches of the same plant (figs. 21, 22). It finds its parallel, under natural circumstances, among the lower cryptogams, in which it often happens that several individual plants, originally distinct, become inseparably blended together into one mass. In the gardening operations of inarching, and to some extent in budding, this adhesion of axis to axis occurs, the union taking place the more readily in proportion as the contact between the younger growing portions of the two axes respectively is close. The huge size of some trees has been, in some cases, attributed to the adnation of different stems. This is said to be the case with the famous plane trees of Bujukdere, near Constantinople, and in which nine trunks are more or less united together.[56]

A similar anastomosis may take place in the roots. Lindley cites a case wherein two carrots, of the white Belgian and the red Surrey varieties respectively, had grown so close to each other that each twisted half round the other, so that they ultimately became soldered together; the most singular thing with reference to this union was, that the red carrot (fig. 23, _b_), with its small overgrown part above the junction, took the colour and large dimensions of the white Belgian (_d_), which, in like manner, with its larger head above the joining (_a_), took the colour and small dimensions of the red one at and below the union (_e d_). The respective qualities of the two roots were thus transposed, while the upper portions or crowns were unaffected: the root of one, naturally weak, became distended and enlarged by the abundant matter poured into it by its new crown; and in like manner the root of the other, naturally vigorous, was starved by insufficient food derived from the new crown, and became diminutive and shrunken (see Synophty).

The explanation of the fact that the stumps of felled fir trees occasionally continue to grow, and to deposit fresh zones of wood over the stump, depends on similar facts. In _Abies pectinata_, says Goeppert,[57] the roots of different individuals frequently unite; hence if one be cut down, its stump may continue to live, being supplied with nourishment from the adjacent trees to which it is adherent by means of its roots.

A not uncommon malformation in mushrooms arises from the confluence of their stalks (fig. 24), and when the union takes place by means of the pilei, it sometimes happens, during growth, that the one fungus is detached from its attachment to the ground, and is borne up with the other, sometimes, even, being found in an inverted position on the top of its fellow.[58]

The garden operations of budding, grafting and inarching have already been alluded to as furnishing illustrations of adhesion, but it may be well to refer briefly to certain other interesting examples of adhesion induced artificially; thus, the employment of the root as a stock, "root-grafting," is now largely practised with some plants, as affording a quicker means of propagation than by cuttings; and a still more curious illustration may be cited in the fact that it has also been found possible to graft a scion on the leaf in the orange.[59]

Mr. Darwin, in his work on the 'Variation of Animals and Plants,' vol. i, p. 395, alludes to the two following remarkable cases of fusion:--"The author of 'Des Jacinthes' (Amsterdam, 1768, p. 124) says that bulbs of blue and red hyacinths may be cut in two, and that they will grow together, and throw up a united stem (and this Mr. Darwin has himself seen), with flowers of the two colours on the opposite sides. But the remarkable point is, that flowers are sometimes produced with the two colours blended together." In the second case related by Mr. Trail, about sixty blue and white potatoes were cut in halves through the eyes or buds, and the halves were then joined, the other buds being destroyed. Union took place, and some of the united tubers produced white, others blue, while some produced tubers partly white and partly blue.

=Adhesion of the axes of plants belonging to different species is a= more singular occurrence than the former, and is of some interest as connected with the operation of grafting. As a general rule horticulturists are of opinion, and their opinion is borne out by facts, that the operation of grafting, to be successful, must be practised on plants of close botanical affinity. On the other hand, it is equally true that some plants very closely allied cannot be propagated in this manner. Contact between the younger growing tissues is essential to successful grafting as practised by the gardener, and is probably quite as necessary in those cases where the process takes place naturally. Although there is little doubt but that some of the recorded instances of natural or artificial grafting of plants of distant botanical affinities are untrustworthy, yet the instances of adhesion between widely different plants are too numerous and too well attested to allow of doubt. Moreover, when parasitical plants are considered, such as the Orobanches, the Cuscutas, and specially the mistleto (_Viscum_), which may be found growing on plants of very varied botanical relationship, the occurrence of occasional adhesion between plants of distant affinity is not so much to be wondered at. Union between the haulms of wheat and rye, and other grasses, has been recorded[60]. Moquin-Tandon[61] relates a case wherein, by accident, a branch of a species of _Sophora_ passed through the fork, made by two diverging branches of an elder (_Sambucus_), growing in the Jardin des Plantes of Toulouse. The branch of the _Sophora_ contracted a firm adhesion to the elder, and what is remarkable is that, although the latter has much softer wood than the former, yet the branch of the harder wooded tree was flattened, as if subjected to great pressure[62]. It is possible that some of the cases similar to those spoken of by Columella, Virgil[63], and other classical writers, may have originated in the accidental admission of seeds into the crevices of trees; in time the seeds grew, and as they did so, the young plants contracted an adhesion to the supporting tree. Some of the instances recorded by classical writers may be attributed to intentional or accidental fallacy, as in the so-called "greffe des charlatans" of more modern days.

Adhesion of the roots of different species has been effected artificially, as between the carrot and the beet root, while Dr. Maclean succeeded in engrafting, on a red beet, a scion of the white Silesian variety of the same species. In all these cases, even in the most successful grafts, the amount of adhesion is very slight; the union in no degree warrants the term fusion, it is little but simple contact of similar tissues, while new growing matter is formed all round the cut surfaces, so that the latter become gradually imbedded in the newly formed matter.

=Synophty or adhesion of the embryo.=--This often occurs partially in the embryo plants of the common mistleto (_Viscum_), but is not of common occurrence in other plants, even in such cases as the orange (_Citrus_), the _Cycadeæ_, _Coniferæ_, &c., where there is frequently more than one embryo in the seed. Alphonse De Candolle has described and figured an instance of the kind in _Euphorbia helioscopia_, wherein two embryo plants were completely grafted together throughout the whole length of their axes, leaving merely the four cotyledons separate. A similar adnation has been observed by the same botanist in _Lepidium sativum_ and _Sinapis ramosa_, as well as in other plants.[64] I have met with corresponding instances in _Antirrhinum majus_ and in _Cratægus oxyacantha_, in the latter case complicated with the partial atrophy of one of the four cotyledons. It is necessary to distinguish between such cases and the fallacious appearances arising from a division of the cotyledons. M. Morren has figured and described the union of two roots of carrot (_Daucus_), which were also spirally twisted. He attributes this union to the blending of two radicles, and applies the term "rhizocollesy" to this union of the roots.[65] Mr. Thwaites cites a case wherein two embryos were contained in one seed in a _Fuchsia_, and had become adherent. What is still more remarkable, the two embryos were different, a circumstance attributable to their hybrid origin, the seed containing them being the result of the fertilisation of _Fuchsia coccinea_ (quere _F. magellanica?_) by the pollen of _F. fulgens_.

FOOTNOTES:

[30] Wydler, 'Flora,' 1852, p. 737, tab. ix.

[31] 'El. Ter. Veg.,' p. 254.

[32] 'Bull. Soc. Bot. Fr.,' 1857, p. 451.

[33] 'Bull. Acad. Belg.,' vol. xix, part ii, p. 335.

[34] 'Bull. Soc. Bot. Fr.,' 1860, p. 25.

[35] 'Bull. Soc. Bot. Fr.,' 1861, p. 147.

[36] 'Bull. Acad. Belg.,' vol. xviii, part ii, p. 498.

[37] See also Prillieux, 'Bull. Soc. Bot. Fr.,' 1861, p. 195.

[38] 'Mém. Acad. Toulouse,' 5th Series, vol. iii.

[39] Linnæa, vol. ii. p. 607.

[40] 'Journal Roy. Hort. Soc.,' new ser., vol. i. 1866, p. 200.

[41] 'Bull. Soc. Bot. Fr.,' 1861, p. 159.

[42] Ibid., 1859, p. 467.

[43] 'Flora,' 1858, p. 65, tab. ii.

[44] C. Morren. 'Bull. Acad. Belg.,' vol. xv (Fuchsia, p. 89); vol. xviii, p. 591. (Lobelia, p. 142); vol. xix, p. 352; vol. xx, p. 4.

[45] 'Bull. Soc. Bot. Fr.,' vol. vii, p. 625.

[46] Cramer, 'Bildungsabweichungen,' p. 56, tab. vii, fig. 10, figures a case wherein the two central flowers of the capitulum of _Centaurea Jacea_ were united together.

[47] 'Bull. Bot.' tab. iii, figs. 4-6.

[48] 'Mém. greffe Ann. Science Nat.,' ser. i, t. xxiv, p. 334.

[49] "Mespilus portentosa." Poit. et Turp., 'Pomol. Franc.,' liv, xxxi, p. 202, pl. 202.

[50] Duchesne, 'Hist. Nat. Frais.,' p. 79.

[51] De Cand., 'Phys. Végét.,' tom. ii, p. 781.

[52] Sched. de monstr. plant. 'Act. Helv.,' tab. i, fig. 8.

[53] 'Mém. greffe,' loc. cit., tab. xxiv, p. 334.

[54] 'Bull. Soc. Bot. Franc.,' 8, pp. 73 and 351, tab. ii; and Röse. 'Bot. Zeit.,' x, p. 410.

[55] _Nymphæa lutea_, _Æsculus Hippocastanum_, &c. See Moquin, 'El. Ter. Veg.,' p. 277.

[56] C. Martins, 'Promenade Botanique,' p. 8.

[57] 'Ann. Sc. Nat.,' t. xix, 1843, p. 141, tab. iv.

[58] 'Ann. Nat. Hist.,' ser. 2, vol. ix, tab. xvi. 'Phytologist,' 1857. p. 352, &c.

[59] Quoted from the 'Revue Hortic.' in 'Gard. Chron.,' 1866, p. 386.

[60] Senebier, 'Phys Végét.,' t. iv, p. 426. The same author also cites Romer as having found two plants of _Ranunculus_, from the stem of which emerged a daisy. As it is not an uncommon practice to stick a daisy on a buttercup, it is to be hoped no hoax was played off on M. Romer.

[61] 'El. Ter. Veg.,' p. 289.

[62] An instance of this kind is cited in Dr. Robson's memoir of the late Charles Waterton, from which it appears that two trees, a spruce fir and an elm, were originally planted side by side, and had been annually twisted round each other, so that they had in places grown one into the other, with the result of stunting the growth of both trees, thus illustrating, according to the opinion of the eccentric naturalist above cited, the incongruous union of Church and State!

[63] See Daubeny, 'Lectures on Roman Husbandry,' p. 156.

[64] A. P. De Candolle, 'Organ Végét.,' t. ii, p. 72, tab. liv, fig. 1.

[65] 'Bull. Acad. Belg.,' t. xx, part i, 1852, p. 43.