The Variation of Animals and Plants Under Domestication. Vol I.

Peach (Amygdalus Persica).—In the last chapter I gave two cases of a peach-almond and double-flowered almond which suddenly produced fruit closely resembling true peaches. I have also recorded many cases of peach-trees producing buds, which, when developed into branches, have yielded nectarines. We have seen that no less than six named and several unnamed varieties of the peach have thus produced several varieties of nectarine. I have shown that it is highly improbable that all these peach-trees, some of which are old varieties, and have been propagated by the million, are hybrids from the peach and nectarine, and that it is opposed to all analogy to attribute the occasional production of nectarines on peach-trees to the direct action of pollen from some neighbouring nectarine-tree. Several of the cases are highly remarkable, because, firstly, the fruit thus produced has sometimes been in part a nectarine and in part a peach; secondly, because nectarines thus suddenly produced have reproduced themselves by seed; and thirdly, because nectarines are produced from peach-trees from seed as well as from buds. The seed of the nectarine, on the other hand, occasionally produces peaches; and we have seen in one instance that a nectarine-tree yielded peaches by bud-variation. As the peach is certainly the oldest or primary variety, the production of peaches from nectarines, either by seeds or buds, may perhaps be considered as a case of reversion. Certain trees have also been described as indifferently bearing peaches or nectarines, and this may be considered as bud-variation carried to an extreme degree.

The grosse mignonne peach at Montreuil produced "from a sporting branch" the grosse mignonne tardive, "a most excellent variety," which ripens its fruit a fortnight later than the parent tree, and is equally good.^[813] This same peach has likewise produced by bud-variation the early grosse mignonne. Hunt's large tawny nectarine "originated from Hunt's small tawny nectarine, but not through seminal reproduction."^[814]

Plums.—Mr. Knight states that a tree of the yellow magnum bonum plum, forty years old, which had always borne ordinary fruit, produced a branch which yielded red magnum bonums.^[815] Mr. Rivers, of Sawbridgeworth, informs me (Jan. 1863) that a single tree out of 400 or 500 trees of the Early Prolific plum, which is a purple kind, descended from an old French variety bearing purple fruit, produced when about ten years old bright yellow plums; these differed in no respect except colour from those on the other trees, but were unlike any other known kind of yellow plum.^[816]

Cherry (Prunus cerasus).—Mr. Knight has recorded (idem) the case of a branch of a May-Duke cherry, which, though certainly never grafted, always produced fruit, ripening later, and more oblong, than the fruit on the other branches. Another account has been given of two May-Duke cherry-trees in Scotland, with branches bearing oblong, and very fine fruit, which invariably ripened, as in Knight's case, a fortnight later than the other cherries.^[817]

Grapes (Vitis vinifera).—The black or purple Frontignan in one case produced during two successive years (and no doubt permanently) spurs which bore white Frontignan grapes. In another case, on the same footstalk, the lower berries "were well-coloured black Frontignans; those next the stalk were white, with the exception of one black and one streaked berry;" and altogether there were fifteen black and twelve white berries on the same stalk. In another kind of grape black and amber-coloured berries were produced in the same cluster.^[818] Count Odart describes a variety which often bears on the same stalk small round and large oblong berries; though the shape of the berry is generally a fixed character.^[819] Here is another striking case given on the excellent authority of M. Carrière:^[820] "a black Hamburgh grape (Frankenthal) was cut down, and produced three suckers; one of these was layered, and after a time produced much smaller berries, which always ripened at least a fortnight earlier than the others. Of the remaining two suckers, one produced every year fine grapes, whilst the other, although it set an abundance of fruit, matured only a few, and these of inferior quality.

Gooseberry (Ribes grossularia).—A remarkable case has been described by Dr. Lindley^[821] of a bush which bore at the same time no less than four kinds of berries, namely, hairy and red,—smooth, small and red,—green,—and yellow tinged with buff; the two latter kinds had a different flavour from the red berries, and their seeds were coloured red. Three twigs on this bush grew close together; the first bore three yellow berries and one red; the second twig bore four yellow and one red; and the third four red and one yellow. Mr. Laxton also informs me that he has seen a Red Warrington gooseberry bearing both red and yellow fruit on the same branch.

Currant (Ribes rubrum).—A bush purchased as the Champagne, which is a variety that bears blush-coloured fruit intermediate between red and white, produced during fourteen years, on separate branches and mingled on the same branch, berries of the red, white, and champagne kinds.^[822] The suspicion naturally arises that this variety may have originated from a cross between a red and white variety, and that the above transformation may be accounted for by reversion to both parent-forms; but from the foregoing complex case of the gooseberry this view is doubtful. In France, a branch of a red-currant bush, about ten years old, produced near the summit five white berries, and lower down, amongst the red berries, one berry half red and half white.^[823] Alexander Braun^[824] also has often seen branches bearing red berries on white currants.

Pear (Pyrus communis).—Dureau de la Malle states that the flowers on some trees of an ancient variety, the doyenné galeux, were destroyed by frost: other flowers appeared in July, which produced six pears; these exactly resembled in their skin and taste the fruit of a distinct variety, the gros doyenné blanc, but in shape were like the bon-chrétien: it was not ascertained whether this new variety could be propagated by budding or grafting. The same author grafted a bon-chrétien on a quince, and it produced, besides its proper fruit, an apparently new variety, of a peculiar form, with thick and rough skin.^[825]

Apple (Pyrus malus).—In Canada, a tree of the variety called Pound Sweet, produced,^[826] between two of its proper fruit, an apple which was well russetted, small in size, different in shape, and with a short peduncle. As no russet apple grew anywhere near, this case apparently cannot be accounted for by the direct action of foreign pollen. I shall hereafter give cases of apple-trees which regularly produce fruit of two kinds, or half-and-half fruit; these trees are generally supposed, and probably with truth, to be of crossed parentage, and that the fruit reverts to both parent-forms.

Banana (Musa sapientium).—Sir R. Schomburgk states that he saw in St. Domingo a raceme on the Fig Banana which bore towards the base 125 fruits of the proper kind; and these were succeeded, as is usual, higher up the raceme, by barren flowers, and these by 420 fruits, having a widely different appearance, and ripening earlier than the proper fruit. The abnormal fruit closely resembled, except in being smaller, that of the Musa Chinensis or Cavendishii, which has generally been ranked as a distinct species.^[827]

Flowers.—Many cases have been recorded of a whole plant, or single branch, or bud, suddenly producing flowers different from the proper type in colour, form, size, doubleness, or other character. Half the flower, or a smaller segment, sometimes changes colour.

Camellia.—The myrtle-leaved species (C. myrtifolia), and two or three varieties of the common species, have been known to produce hexagonal and imperfectly quadrangular flowers; and the branches producing such flowers have been propagated by grafting.^[828] The Pompone variety often bears "four distinguishable kinds of flowers,—the pure white and the red-eyed, which appear promiscuously; the brindled pink and the rose-coloured, which may be kept separate with tolerable certainty by grafting from the branches that bear them." A branch, also, on an old tree of the rose-coloured variety has been seen to "revert to the pure white colour, an occurrence less common than the departure from it."^[829]

Cratægus oxycantha.—A dark pink hawthorn has been known to throw out a single tuft of pure white blossoms;^[830] and Mr. A. Clapham, nurseryman, of Bradford, informs me that his father had a deep crimson thorn grafted on a white thorn, which, during several years, always bore, high above the graft, bunches of white, pink, and deep crimson flowers.

Azalea Indica is well known often to produce by buds new varieties. I have myself seen several cases. A plant of Azalea Indica variegata has been exhibited bearing a truss of flowers of A. Ind. Gledstanesii "as true as could possibly be produced, thus evidencing the origin of that fine variety." On another plant of A. Ind. variegata a perfect flower of A. Ind. lateritia was produced; so that both Gledstanesii and lateritia no doubt originally appeared as sporting branches of A. Ind. variegata.^[831]

Cistus tricuspis.—A seedling of this plant, when some years old, produced, at Saharunpore,^[832] some branches "which bore leaves and flowers widely different from the normal form." "The abnormal leaf is much less divided, and not acuminated. The petals are considerably larger, and quite entire. There is also in the fresh state a conspicuous, large, oblong gland, full of a viscid secretion, on the back of each of the calycine segments."

Althæa rosea.—A double yellow Hollyock suddenly turned one year into a pure white single kind; subsequently a branch bearing the original double yellow flowers reappeared in the midst of the branches of the single white kind.^[833]

Pelargonium.—These highly cultivated plants seem eminently liable to bud-variation. I will give only a few well-marked cases. Gärtner has seen^[834] a plant of P. zonale with a branch having white-edged leaves, which remained constant for years, and bore flowers of a deeper red than usual. Generally speaking, such branches present little or no difference in their flowers: thus a writer^[835] pinched off the leading shoot of a seedling P. zonale, and it threw out three branches, which differed in the size and colour of their leaves and stems; but on all three branches "the flowers were identical," except in being largest in the green-stemmed variety, and smallest in that with variegated foliage: these three varieties were subsequently propagated and distributed. Many branches, and some whole plants, of a variety called compactum, which bears orange-scarlet flowers, have been seen to produce pink flowers.^[836] Hill's Hector, which is a pale red variety, produced a branch with lilac flowers, and some trusses with both red and lilac flowers. This apparently is a case of reversion, for Hill's Hector was a seedling from a lilac variety.^[837] Of all Pelargoniums, Rollisson's Unique seems to be the most sportive; its origin is not positively known, but is believed to be from a cross. Mr. Salter, of Hammersmith, states^[838] that he has himself known this purple variety to produce the lilac, the rose-crimson or conspicuum, and the red or coccineum varieties; the latter has also produced the rose d'amour; so that altogether four varieties have originated by bud variation from Rollisson's Unique. Mr. Salter remarks that these four varieties "may now be considered as fixed, although they occasionally produce flowers of the original colour. This year coccineum has pushed flowers of three different colours, red, rose, and lilac, upon the same truss, and upon other trusses are flowers half red and half lilac." Besides these four varieties, two other scarlet Uniques are known to exist, both of which occasionally produce lilac flowers identical with Rollisson's Unique;^[839] but one at least of these did not arise through bud-variation, but is believed to be a seedling from Rollisson's Unique.^[840] There are, also, in the trade^[841] two other slightly different varieties, of unknown origin, of Rollisson's Unique: so that altogether we have a curiously complex case of variation both by buds and seeds.^[842] An English wild plant, the Geranium pratense, when cultivated in a garden, has been seen to produce on the same plant both blue and white, and striped blue and white flowers.^[843]

Chrysanthemum.—This plant frequently sports, both by its lateral branches and occasionally by suckers. A seedling raised by Mr. Salter has produced by bud-variation six distinct sorts, five different in colour and one in foliage, all of which are now fixed.^[844] The varieties which were first introduced from China were so excessively variable, "that it was extremely difficult to tell which was the original colour of the variety, and which was the sport." The same plant would produce one year only buff-coloured, and next year only rose-coloured flowers; and then would change again, or produce at the same time flowers of both colours. These fluctuating varieties are now all lost, and, when a branch sports into a new variety, it can generally be propagated and kept true; but, as Mr. Salter remarks, "every sport should be thoroughly tested in different soils before it can be really considered as fixed, as many have been known to run back when planted in rich compost; but when sufficient care and time are expended in proving, there will exist little danger of subsequent disappointment." Mr. Salter informs me that with all the varieties the commonest kind of bud-variation is the production of yellow flowers, and, as this is the primordial colour, these cases may be attributed to reversion. Mr. Salter has given me a list of seven differently coloured chrysanthemums, which have all produced branches with yellow flowers; but three of them have also sported into other colours. With any change of colour in the flower, the foliage generally changes in a corresponding manner in lightness or darkness.

Another Compositous plant, namely, Centauria cyanus, when cultivated in a garden, not unfrequently produces on the same root flowers of four different colours, viz., blue, white, dark-purple, and particoloured.^[845] The flowers of Anthemis also vary on the same plant.^[846]

Roses.—Many varieties of the rose are known or are believed to have originated by bud-variation.^[847] The common double moss-rose was imported into England from Italy about the year 1735.^[848] Its origin is unknown, but from analogy it probably arose from the Provence rose (R. centifolia) by bud-variation; for branches of the common moss-rose have several times been known to produce Provence roses, wholly or partially destitute of moss: I have seen one such instance, and several others have been recorded.^[849] Mr. Rivers also informs me that he raised two or three roses of the Provence class from seed of the old single moss-rose;^[850] and this latter kind was produced in 1807 by bud-variation from the common moss-rose. The white moss-rose was also produced in 1788 by an offset from the common red moss-rose: it was at first pale blush-coloured, but became white by continued budding. On cutting down the shoots which had produced this white moss-rose, two weak shoots were thrown up, and buds from these yielded the beautiful striped moss-rose. The common moss-rose has yielded by bud-variation, besides the old single red moss-rose, the old scarlet semi-double moss-rose, and the sage-leaf moss-rose, which "has a delicate shell-like form, and is of a beautiful blush colour; it is now (1852) nearly extinct."^[851] A white moss-rose has been seen to bear a flower half white and half pink.^[852] Although several moss-roses have thus certainly arisen by bud-variation, the greater number probably owe their origin to seed of moss-roses. For Mr. Rivers informs me that his seedlings from the old single moss-rose almost always produced moss-roses; and the old single moss-rose was, as we have seen, the product by bud-variation of the double moss-rose originally imported from Italy. That the original moss-rose was the product of bud-variation is probable, from the facts above given and from the moss-rose de Meaux (also a var. of R. centifolia)^[853] having appeared as a sporting branch on the common rose de Meaux.

Prof. Caspary has carefully described^[854] the case of a six-year-old white moss-rose, which sent up several suckers, one of which was thorny, and produced red flowers, destitute of moss, exactly like those of the Provence rose (R. centifolia): another shoot bore both kinds of flowers and in addition longitudinally striped flowers. As this white moss-rose had been grafted on the Provence rose, Prof. Caspary attributes the above changes to the influence of the stock; but from the facts already given, and from others to be given, bud-variation, with reversion, is probably a sufficient explanation.

Many other instances could be added of roses varying by buds. The white Provence rose apparently thus originated.^[855] The double and highly-coloured Belladonna rose has been known^[856] to produce by suckers both semi-double and almost single white roses; whilst suckers from one of these semi-double white roses reverted to perfectly characterised Belladonnas. Varieties of the China rose propagated by cuttings in St. Domingo often revert after a year or two into the old China rose.^[857] Many cases have been recorded of roses suddenly becoming striped or changing their character by segments: some plants of the Comtesse de Chabrillant, which is properly rose-coloured, were exhibited in 1862,^[858] with crimson flakes on a rose ground. I have seen the Beauty of Billiard with a quarter and with half the flower almost white. The Austrian bramble (R. lutea) not rarely^[859] produces branches with pure yellow flowers; and Prof. Henslow has seen exactly half the flower of a pure yellow, and I have seen narrow yellow streaks on a single petal, of which the rest was of the usual copper colour.

The following cases are highly remarkable. Mr. Rivers, as I am informed by him, possessed a new French rose with delicate smooth shoots, pale glaucous-green leaves, and semi-double pale flesh-coloured flowers striped with dark red; and on branches thus characterised there suddenly appeared, in more than one instance, the famous old rose called the Baronne Prevost, with its stout thorny shoots, and immense, uniformly and richly coloured, double flowers; so that in this case the shoots, leaves, and flowers, all at once changed their character by bud-variation. According to M. Verlot^[860] a variety called Rosa cannabifolia, which has peculiarly shaped leaflets, and differs from every member of the family in the leaves being opposite instead of alternate, suddenly appeared on a plant of R. alba in the gardens of the Luxembourg. Lastly, "a running shoot" was observed by Mr. H. Curtis^[861] on the old Aimée Vibert Noisette, and he budded it on Celine; thus a climbing Aimée Vibert was first produced and afterwards propagated.

Dianthus.—It is quite common with the Sweet William (D. barbatus) to see differently coloured flowers on the same root; and I have observed on the same truss four differently coloured and shaded flowers. Carnations and pinks (D. caryophyllus, &c.) occasionally vary by layers; and some kinds are so little certain in character that they are called by floriculturists "catch-flowers."^[862] Mr. Dickson has ably discussed the "running" of particoloured or striped carnations, and says it cannot be accounted for by the compost in which they are grown: "layers from the same clean flower would come part of them clean and part foul, even when subjected to precisely the same treatment; and frequently one flower alone appears influenced by the taint, the remainder coming perfectly clean."^[863] This running of the parti-coloured flowers apparently is a case of reversion by buds to the original uniform tint of the species.

I will briefly mention some other cases of bud-variation to show how many plants belonging to many orders have varied in their flowers; numerous cases might be added. I have seen on a snap-dragon (Antirrhinum majus) white, pink, and striped flowers on the same plant, and branches with striped flowers on a red-coloured variety. On a double stock (Matthiola incana) I have seen a branch bearing single flowers; and on a dingy-purple, double variety of the wall-flower (Cheiranthus cheiri) a branch which had reverted to the ordinary copper colour. On other branches of the same plant, some flowers were exactly divided across the middle, one half being purple and the other coppery; but some of the smaller petals towards the centre of these same flowers were purple longitudinally streaked with coppery colour, or coppery streaked with purple. A Cyclamen^[864] has been observed to bear white and pink flowers of two forms, the one resembling the Persicum strain, and the other the Coum strain. Oenothera biennis has been seen^[865] bearing flowers of three different colours. The hybrid Gladiolus colvillii occasionally bears uniformly coloured flowers, and one case is recorded^[866] of all the flowers on a plant thus changing colour. A Fuchsia has been seen^[867] bearing two kinds of flowers. Mirabilis jalapa is eminently sportive, sometimes bearing on the same root pure red, yellow, and white flowers, and others striped with various combinations of these three colours.^[868] The plants of the Mirabilis which bear such extraordinarily variable flowers, in most, probably in all cases, owe their origin, as shown by Prof. Lecoq, to crosses between differently-coloured varieties.

Leaves and Shoots.—Changes, through bud-variation, in fruits and flowers have hitherto been treated of, but incidentally some remarkable modifications in the leaves and shoots of the rose and Cistus, and in a lesser degree in the foliage of the Pelargonium and Chrysanthemum, have been noticed. I will now add a few more cases of variation in leaf-buds. Verlot^[869] states that on Aralia trifoliata, which properly has leaves with three leaflets, branches bearing simple leaves of various forms frequently appear; these can be propagated by buds or grafting, and have given rise, as he states, to several nominal species.

With respect to trees, the history of but few of the many varieties with curious or ornamental foliage is known; but several probably have originated by bud-variation. Here is one case:—An old ash-tree (Fraxinus excelsior) in the grounds of Necton, as Mr. Mason states, "for many years has had one bough of a totally different character to the rest of the tree, or of any other ash-tree which I have seen; being short-jointed and densely covered with foliage." It was ascertained that this variety could be propagated by grafts.^[870] The varieties of some trees with cut leaves, as the oak-leaved laburnum, the parsley-leaved vine, and especially the fern-leaved beech, are apt to revert by buds to the common form.^[871] The fern-like leaves of the beech sometimes revert only partially, and the branches display here and there sprouts bearing common leaves, fern-like, and variously shaped leaves. Such cases differ but little from the so-called heterophyllous varieties, in which the tree habitually bears leaves of various forms; but it is probable that most heterophyllous trees have originated as seedlings. There is a sub-variety of the weeping willow with leaves rolled up into a spiral coil; and Mr. Masters states that a tree of this kind kept true in his garden for twenty-five years, and then threw out a single upright shoot bearing flat leaves.^[872]

I have often noticed single twigs and branches on beech and other trees with their leaves fully expanded before those on the other branches had opened; and as there was nothing in their exposure or character to account for this difference, I presume that they had appeared as bud-variations, like the early and late fruit-maturing varieties of the peach and nectarine.

Cryptogamic plants are liable to bud-variation, for fronds on the same fern are often seen to display remarkable deviations of structure. Spores, which are of the nature of buds, taken from such abnormal fronds, reproduce, with remarkable fidelity, the same variety, after passing through the sexual stage.^[873]

With respect to colour, leaves often become by bud-variation zoned, blotched, or spotted with white, yellow, and red; and this occasionally occurs even with plants in a state of nature. Variegation, however, appears still more frequently in plants produced from seed; even the cotyledons or seed-leaves being thus affected.^[874] There have been endless disputes whether variegation should be considered as a disease. In a future chapter we shall see that it is much influenced, both in the case of seedlings and of mature plants, by the nature of the soil. Plants which have become variegated as seedlings, generally transmit their character by seed to a large proportion of their progeny; and Mr. Salter has given me a list of eight genera in which this occurred.^[875] Sir F. Pollock has given me more precise information: he sowed seed from a variegated plant of Ballota nigra which was found growing wild, and thirty per cent. of the seedlings were variegated; seed from these latter being sown, sixty per cent. came up variegated. When branches become variegated by bud-variation, and the variety is attempted to be propagated by seed, the seedlings are rarely variegated; Mr. Salter found this to be the case with plants belonging to eleven genera, in which the greater number of the seedlings proved to be green-leaved; yet a few were slightly variegated, or were quite white, but none were worth keeping. Variegated plants, whether originally produced from seeds or buds, can generally be propagated by budding, grafting, &c.; but all are apt to revert by bud-variation to their ordinary foliage. This tendency, however, differs much in the varieties of even the same species; for instance, the golden-striped variety of Euonymus Japonicus "is very liable to run back to the green-leaved, while the silver-striped variety hardly ever changes."^[876] I have seen a variety of the holly, with its leaves having a central yellow patch, which had everywhere partially reverted to the ordinary foliage, so that on the same small branch there were many twigs of both kinds. In the pelargonium, and in some other plants, variegation is generally accompanied by some degree of dwarfing, as is well exemplified in the "Dandy" pelargonium. When such dwarf varieties sport back by buds or suckers to the ordinary foliage, the dwarfed stature sometimes still remains.^[877] It is remarkable that plants propagated from branches which have reverted from variegated to plain leaves^[878] do not always (or never, as one observer asserts) perfectly resemble the original plain-leaved plant from which the variegated branch arose: it seems that a plant, in passing by bud-variation from plain leaves to variegated, and back again from variegated to plain, is generally in some degree affected so as to assume a slightly different aspect.

Bud-variation by Suckers, Tubers, and Bulbs.—All the cases hitherto given of bud-variation in fruits, flowers, leaves, and shoots, have been confined to buds on the stems or branches, with the exception of a few cases incidentally noticed of varying suckers in the rose, pelargonium, and chrysanthemum. I will now give a few instances of variation in subterranean buds, that is, by suckers, tubers, and bulbs; not that there is any essential difference between buds above and beneath the ground. Mr. Salter informs me that two variegated varieties of Phlox originated as suckers; but I should not have thought these worth mentioning, had not Mr. Salter found, after repeated trials, that he could not propagate them by "root-joints," whereas, the variegated Tussilago farfara can thus be safely propagated;^[879] but this latter plant may have originated as a variegated seedling, which would account for its greater fixedness of character. The Barberry (Berberis vulgaris) offers an analogous case; there is a well-known variety with seedless fruit, which can be propagated by cuttings or layers; but suckers always revert to the common form, which produces fruit containing seeds.^[880] My father repeatedly tried this experiment, and always with the same result.

Turning now to tubers: in the common Potato (Solanum tuberosum) a single bud or eye sometimes varies and produces a new variety; or, occasionally, and this is a much more remarkable circumstance, all the eyes in a tuber vary in the same manner and at the same time, so that the whole tuber assumes a new character. For instance, a single eye in a tuber of the old Forty-fold potato, which is a purple variety, was observed^[881] to become white; this eye was cut out and planted separately, and the kind has since been largely propagated. Kemp's Potato is properly white, but a plant in Lancashire produced two tubers which were red, and two which were white; the red kind was propagated in the usual manner by eyes, and kept true to its new colour, and, being found a more productive variety, soon became widely known under the name of Taylor's Forty-fold.^[882] The Old Forty-fold potato, as already stated, is a purple variety; but a plant long cultivated on the same ground produced, not as in the case above given a single white eye, but a whole white tuber, which has since been propagated and keeps true.^[883] Several cases have been recorded of large portions of whole rows of potatoes slightly changing their character.^[884]

Dahlias propagated by tubers under the hot climate of St. Domingo vary much; Sir R. Schomburgk gives the case of the "Butterfly variety," which the second year produced on the same plant "double and single flowers; here white petals edged with maroon; there of a uniform deep maroon."^[885] Mr. Bree also mentions a plant "which bore two different kinds of self-coloured flowers, as well as a third kind which partook of both colours beautifully intermixed."^[886] Another case is described of a dahlia with purple flowers which bore a white flower streaked with purple.^[887]

Considering how long and extensively many Bulbous plants have been cultivated, and how numerous are the varieties produced from seed, these plants have not varied so much by offsets,—that is, by the production of new bulbs,—as might have been expected. With the Hyacinth a case has been recorded of a blue variety which for three successive years gave offsets which produced white flowers with a red centre.^[888] Another hyacinth has been described^[889] as bearing on the same truss a perfectly pink and a perfectly blue flower.

Mr. John Scott informs me that in 1862 Imatophyllum miniatum, in the Botanic Gardens of Edinburgh, threw up a sucker which differed from the normal form, in the leaves being two-ranked instead of four-ranked. The leaves were also smaller, with the upper surface raised instead of being channelled.

In the propagation of Tulips, seedlings are raised, called selfs or breeders, which "consist of one plain colour on a white or yellow bottom. These, being cultivated on a dry and rather poor soil, become broken or variegated and produce new varieties. The time that elapses before they break varies from one to twenty years or more, and sometimes this change never takes place."^[890] The various broken or variegated colours which give value to all tulips are due to bud-variation; for although the Bybloemens and some other kinds have been raised from several distinct breeders, yet all the Baguets are said to have come from a single breeder or seedling. This bud-variation, in accordance with the views of MM. Vilmorin and Verlot,^[891] is probably an attempt to revert to that uniform colour which is natural to the species. A tulip, however, which has already become broken, when treated with too strong manure, is liable to flush or lose by a second act of reversion its variegated colours. Some kinds, as Imperatrix Florum, are much more liable than others to flushing; and Mr. Dickson maintains^[892] that this can no more be accounted for than the variation of any other plant. He believes that English growers, from care in choosing seed from broken flowers instead of from plain flowers, have to a certain extent diminished the tendency in flowers already broken to flushing or secondary reversion.

During two consecutive years all the early flowers in a bed of Tigridia conchiflora^[893] resembled those of the old T. pavonia; but the later flowers assumed their proper colour of fine yellow spotted with crimson. An apparently authentic account has been published^[894] of two forms of Hemerocallis, which have been universally considered as distinct species, changing into each other; for the roots of the large-flowered tawny H. fulva, being divided and planted in a different soil and place, produced the small-flowered yellow H. flava, as well as some intermediate forms. It is doubtful whether such cases as these latter, as well as the "flushing" of broken tulips and the "running" of particoloured carnations,—that is, their more or less complete return to a uniform tint,—ought to be classed under bud-variation, or ought to be retained for the chapter in which I treat of the direct action of the conditions of life on organic beings. These cases, however, have this much in common with bud-variation, that the change is effected through buds and not through seminal reproduction. But, on the other hand, there is this difference—that in ordinary cases of bud-variation, one bud alone changes, whilst in the foregoing cases all the buds on the same plant were modified together; yet we have an intermediate case, for with the potato all the eyes in one tuber alone simultaneously changed their character.

I will conclude with a few allied cases, which may be ranked either under bud-variation, or under the direct action of the conditions of life. When the common Hepatica is transplanted from its native woods, the flowers change colour, even during the first year.^[895] It is notorious that the improved varieties of the Heartsease (Viola tricolor) when transplanted often produce flowers widely different in size, form, and colour: for instance, I transplanted a large uniformly-coloured dark purple variety, whilst in full flower, and it then produced much smaller, more elongated flowers, with the lower petals yellow; these were succeeded by flowers marked with large purple spots, and ultimately, towards the end of the same summer, by the original large dark purple flowers. The slight changes which some fruit-trees undergo from being grafted and regrafted on various stocks,^[896] were considered by Andrew Knight^[897] as closely allied to "sporting branches," or bud-variations. Again, we have the case of young fruit-trees changing their character as they grow old; seedling pears, for instance, lose with age their spines and improve in the flavour of their fruit. Weeping birch-trees, when grafted on the common variety, do not acquire a perfect pendulous habit until they grow old: on the other hand, I shall hereafter give the case of some weeping ashes which slowly and gradually assumed an upright habit of growth. All such changes, dependent on age, may be compared with the changes, alluded to in the last chapter, which many trees naturally undergo; as in the case of the Deodar and Cedar of Lebanon, which are unlike in youth and closely resemble each other in old age; and as with certain oaks, and with some varieties of the lime and hawthorn.^[898]

Throughout Europe, in different soils and under different climates, branches on this tree have repeatedly and suddenly reverted to both parent-species in their flowers and leaves. To behold mingled on the same tree tufts of dingy-red, bright yellow, and purple flowers, borne on branches having widely different leaves and manner of growth, is a surprising sight. The same raceme sometimes bears two kinds of flowers; and I have seen a single flower exactly divided into halves, one side being bright yellow and the other purple; so that one half of the standard-petal was yellow and of larger size, and the other half purple and smaller. In another flower the whole corolla was bright yellow, but exactly half the calyx was purple. In another, one of the dingy-red wing-petals had a bright yellow narrow stripe on it; and lastly, in another flower, one of the stamens, which had become slightly foliaceous, was half yellow and half purple; so that the tendency to segregation of character or reversion affects even single parts and organs.^[899] The most remarkable fact about this tree is that in its intermediate state, even when growing near both parent-species, it is quite sterile; but when the flowers become pure yellow or pure purple they yield seed. I believe that the pods from the yellow flowers yield a full complement of seed; they certainly yield a large number. Two seedlings raised by Mr. Herbert from such seed^[900] exhibited a purple tinge on the stalks of their flowers; but several seedlings raised by myself resembled in every character the common laburnum, with the exception that some of them had remarkably long racemes: these seedlings were perfectly fertile. That such purity of character and fertility should be suddenly reacquired from so hybridized and sterile a form is an astonishing phenomenon. The branches with purple flowers appear at first sight exactly to resemble those of C. purpureus; but on careful comparison I found that they differed from the pure species in the shoots being thicker, the leaves a little broader, and the flowers slightly shorter, with the corolla and calyx less brightly purple: the basal part of the standard-petal also plainly showed a trace of the yellow stain. So that the flowers, at least in this instance, had not perfectly recovered their true character; and in accordance with this, they were not perfectly fertile, for many of the pods contained no seed, some produced one, and very few contained as many as two seeds; whilst numerous pods on a tree of the pure C. purpureus in my garden contained three, four, and five fine seeds. The pollen, moreover, was very imperfect, a multitude of grains being small and shrivelled; and this is a singular fact; for, as we shall immediately see, the pollen-grains in the dingy-red and sterile flowers on the parent-tree, were, in external appearance, in a much better state, and included very few shrivelled grain. Although the pollen of the reverted purple flowers was in so poor a condition, the ovules were well-formed, and, when mature, germinated freely with me. Mr. Herbert also raised plants from seeds of the reverted purple flowers, and they differed very little from the usual state of C. purpureus; but this expression shows that they had not perfectly recovered their proper character.

Prof. Caspary has examined the ovules of the dingy-red and sterile flowers in several plants of C. adami on the Continent,^[901] and finds them generally monstrous. In three plants examined by me in England, the ovules were likewise monstrous, the nucleus varying much in shape, and projecting irregularly beyond the proper coats. The pollen-grains, on the other hand, judging from their external appearance, were remarkably good, and readily protruded their tubes. By repeatedly counting, under the microscope, the proportional number of bad grains, Prof. Caspary ascertained that only 2.5 per cent. were bad, which is a less proportion than in the pollen of three pure species of Cytisus in their cultivated state, viz. C. purpureus, laburnum, and alpinus. Although the pollen of C. adami is thus in appearance good, it does not follow, according to M. Naudin's observations^[902] on Mirabilis, that it would be functionally effective. The fact of the ovules of C. adami being monstrous, and the pollen apparently sound, is all the more remarkable, because it is opposed to what usually occurs not only with most hybrids,^[903] but with two hybrids in the same genus, namely in C. purpureo-elongatus, and C. alpino-laburnum. In both these hybrids, the ovules, as observed by Prof. Caspary and myself, were well-formed, whilst many of the pollen-grains were ill-formed; in the latter hybrid 20.3 per cent., and in the former no less than 84.8 per cent. of the grains were ascertained by Prof. Caspary to be bad. This unusual condition of the male and female reproductive elements in C. adami has been used by Prof. Caspary as an argument against this plant being considered as an ordinary hybrid produced from seed; but we should remember that with hybrids the ovules have not been examined nearly so frequently as the pollen, and they may be much oftener imperfect than is generally supposed. Dr. E. Bornet, of Antibes, informs me (through Mr. J. Traherne Moggridge) that with hybrid Cisti the ovarium is frequently deformed, the ovules being in some cases quite absent, and in other cases incapable of fertilisation.

Several theories have been propounded to account for the origin of C. adami, and for the transformations which it undergoes. These transformations have been attributed by some authors to simple bud-variation; but considering the wide difference between C. laburnum and purpureus, both of which are natural species, and considering the sterility of the intermediate form, this view may be summarily rejected. We shall presently see that, with hybrid plants, two different embryos may be developed within the same seed and cohere; and it has been supposed that C. adami might have thus originated. It is known that when a plant with variegated leaves is budded on a plain stock, the latter is sometimes affected, and it is believed by some that the laburnum has been thus affected. Thus Mr. Purser states^[904] that a common laburnum-tree in his garden, into which three grafts of the Cytisus purpureus had been inserted, gradually assumed the character of C. adami; but more evidence and copious details would be requisite to make so extraordinary a statement credible.

Many authors maintain that C. adami is a hybrid produced in the common way by seed, and that it has reverted by buds to its two parent-forms. Negative results are of little value; but Reisseck, Caspary, and I myself, tried in vain to cross C. laburnum and purpureus; when I fertilised the former with pollen of the latter, I had the nearest approach to success, for pods were formed, but in sixteen days after the withering of the flowers they fell off. Nevertheless, the belief that C. adami is a spontaneously produced hybrid between these two species is strongly supported by the fact that hybrids between these species and two others have spontaneously arisen. In a bed of seedlings from C. elongatus, which grew near to C. purpureus, and was probably fertilised by it, through the agency of insects (for these, as I know by experiment, play an important part in the fertilisation of the laburnum), the sterile hybrid C. purpureo-elongatus appeared.^[905] Thus, also, Waterer's laburnum, the C. alpino-laburnum,^[906] spontaneously appeared, as I am informed by Mr. Waterer, in a bed of seedlings.

On the other hand, we have a clear and distinct account given by M. Adam, who raised the plant, to Poiteau,^[907] showing that C. adami is not an ordinary hybrid. M. Adam inserted in the usual manner a shield of the bark of C. purpureus into a stock of C. laburnum; and the bud lay dormant, as often happens, for a year; the shield then produced many buds and shoots, one of which grew more upright and vigorous with larger leaves than the shoots of C. purpureus, and was consequently propagated. Now it deserves especial notice that these plants were sold by M. Adam, as a variety of C. purpureus, before they had flowered; and the account was published by Poiteau after the plants had flowered, but before they had exhibited their remarkable tendency to revert into the two parent-species. So that there was no conceivable motive for falsification, and it is difficult to see how there could have been any error. If we admit as true M. Adam's account, we must admit the extraordinary fact that two distinct species can unite by their cellular tissue, and subsequently produce a plant bearing leaves and sterile flowers intermediate in character between the scion and stock, and producing buds liable to reversion; in short, resembling in every important respect a hybrid formed in the ordinary way by seminal reproduction. Such plants, if really thus formed, might be called graft-hybrids.

I will now give all the facts which I have been able to collect illustrative of the above theories, not for the sake of merely throwing light on the origin of C. adami, but to show in how many extraordinary and complex methods one kind of plant may affect another, generally in connection with bud-variation. The supposition that either C. laburnum or purpureus produced by ordinary bud-variation the intermediate and the other form, may, as already remarked, be absolutely excluded, from the want of any evidence, from the great amount of change thus implied, and from the sterility of the intermediate form. Nevertheless such cases as nectarines suddenly appearing on peach-trees, occasionally with the fruit half-and-half in nature,—moss-roses appearing on other roses, with the flowers divided into halves, or striped with different colours,—and other such cases, are closely analogous in the result produced, though not in origin, with the case of C. adami.

A distinguished botanist, Mr. G. H. Thwaites,^[908] has recorded a remarkable case of a seed from Fuchsia coccinea fertilised by F. fulgens, which contained two embryos, and was "a true vegetable twin." The two plants produced from the two embryos were "extremely different in appearance and character," though both resembled other hybrids of the same parentage produced at the same time. These twin plants "were closely coherent, below the two pairs of cotyledon-leaves, into a single cylindrical stem, so that they had subsequently the appearance of being branches on one trunk." Had the two united stems grown up to their full height, instead of dying, a curiously mixed hybrid would have been produced; but even if some of the buds had subsequently reverted to both parent-forms, the case, although more complex, would not have been strictly analogous with that of C. adami. On the other hand, a mongrel melon described by Sageret^[909] perhaps did thus originate; for the two main branches, which arose from two cotyledon-buds, produced very different fruit,—on the one branch like that of the paternal variety, and on the other branch to a certain extent like that of the maternal variety, the melon of China.

The famous bizzarria Orange offers a strictly parallel case to that of Cytisus adami. The gardener who in 1644 in Florence raised this tree, declared that it was a seedling which had been grafted; and after the graft had perished, the stock sprouted and produced the bizzarria. Gallesio, who carefully examined several living specimens and compared them with the description given by the original describer P. Nato,^[910] states that the tree produces at the same time leaves, flowers, and fruit, identical with the bitter orange and with the citron of Florence, and likewise compound fruit with the two kinds either blended together, both externally and internally, or segregated in various ways. This tree can be propagated by cuttings, and retains its diversified character. The so-called trifacial orange of Alexandria and Smyrna^[911] resembles in its general nature the bizzarria, but differs from it in the sweet orange and citron being blended together in the same fruit, and separately produced on the same tree: nothing is known of its origin. In regard to the bizzarria, many authors believe that it is a graft-hybrid; Gallesio on the other hand thinks that it is an ordinary hybrid, with the habit of partially reverting by buds to the two parent-forms; and we have seen in the last chapter that the species in this genus often cross spontaneously.

Here is another analogous, but doubtful case. A writer in the 'Gardener's Chronicle'^[912] states that an Æsculus rubicunda in his garden yearly produced on one of its branches "spikes of pale yellow flowers, smaller in size and somewhat similar in colour to those of Æ. flava." If as the editor believes Æsculus rubicunda is a hybrid descended on one side from Æ. flava, we have a case of partial reversion to one of the parent-forms. If, as some botanists maintain, Æ. rubicunda is not a hybrid, but a natural species, the case is one of simple bud-variation.

The following facts show that hybrids produced from seed in the ordinary way, certainly sometimes revert by buds to their parent-forms. Hybrids between Tropæolum minus and majus^[913] at first produced flowers intermediate in size, colour, and structure between their two parents; but later in the season some of these plants produced flowers in all respects like those of the mother-form, mingled with flowers still retaining the usual intermediate condition. A hybrid Cereus between C. speciosissimus and phyllanthus,^[914] plants which are widely different in appearance, produced for the first three years angular, five-sided stems, and then some flat stems like those of C. phyllanthus. Kölreuter also gives cases of hybrid Lobelias and Verbascums, which at first produced flowers of one colour, and later in the season flowers of a different colour.^[915] Naudin^[916] raised forty hybrids from Datura lævis fertilised by D. stramonium; and three of these hybrids produced many capsules, of which a half, or quarter, or lesser segment was smooth and of small size like the capsule of the pure D. lævis, the remaining part being spinose and of larger size like the capsule of the pure D. stramonium: from one of these composite capsules, plants were raised which perfectly resembled both parent-forms.

Turning now to varieties. A seedling apple, conjectured to be of crossed parentage, has been described in France,^[917] which bears fruit, with one half larger than the other, of a red colour, acid taste, and peculiar odour; the other side being greenish-yellow and very sweet: it is said scarcely ever to include perfectly developed seed. I suppose that this is not the same tree with that which Gaudichaud^[918] exhibited before the French Institute, bearing on the same branch two distinct kinds of apples, one a reinette rouge, and the other like a reinette canada jaunâtre: this double-bearing variety can be propagated by grafts, and continues to produce both kinds; its origin is unknown. The Rev. J. D. La Touche sent me a coloured drawing of an apple which he brought from Canada, of which half, surrounding and including the whole of the calyx and the insertion of the footstalk, is green, the other half being brown and of the nature of the pomme gris apple, with the line of separation between the two halves exactly defined. The tree was a grafted one, and Mr. La Touche thinks that the branch which bore this curious apple sprung from the point of junction of the graft and stock: had this fact been ascertained, the case would probably have come into the small class of graft-hybrids presently to be given. But the branch may have sprung from the stock, which no doubt was a seedling.

Prof. H. Lecoq, who has made a great number of crosses between the differently coloured varieties of Mirabilis jalapa,^[919] finds that in the seedlings the colours rarely combine, but form distinct stripes; or half the flower is of one colour and half of a different colour. Some varieties regularly bear flowers striped with yellow, white, and red; but plants of such varieties occasionally produce on the same root branches with uniformly coloured flowers of all three tints, and other branches with half-and-half coloured flowers and others with marbled flowers. Gallesio^[920] crossed reciprocally white and red carnations, and the seedlings were striped; but some of the striped plants also bore entirely white and entirely red flowers. Some of these plants produced one year red flowers alone, and in the following year striped flowers; or conversely, some plants, after having borne for two or three years striped flowers, would revert and bear exclusively red flowers. It may be worth mentioning that I fertilised the Purple Sweet-pea (Lathyrus odoratus) with pollen from the light-coloured Painted Lady: seedlings raised from one and the same pod were not intermediate in character, but perfectly resembled both parents. Later in the summer, the plants which had at first borne flowers identical with those of the Painted Lady, produced flowers streaked and blotched with purple; showing in these darker marks a tendency to reversion to the mother-variety. Andrew Knight^[921] fertilised two white grapes with pollen of the Aleppo grape, which is darkly variegated both in its leaves and fruit. The result was that the young seedlings were not at first variegated, but all became variegated during the succeeding summer; besides this, many produced on the same plant bunches of grapes which were all black, or all white, or lead-coloured striped with white, or white dotted with minute black stripes; and grapes of all these shades could frequently be found on the same footstalk.

CHAPTER XI.