Charles Darwin

“ The law of analogous variation holds good with varieties produced by buds, as with those produced from seed: more than one kind of rose has sported into a moss-rose; more than one kind of camellia has assumed an hexagonal form; and at least seven or eight varieties of the peach have produced nectarines.
The laws of inheritance seem to be nearly the same with seminal and bud-varieties. We know how commonly reversion comes into play with both, and it may affect the whole, or only segments, of a leaf, flower, or fruit. ”

“ The difference between seminal and bud reproduction is not so great as it at first appears; for each bud is in one sense a new and distinct individual; but such individuals are produced through the formation of various kinds of buds without the aid of any special apparatus, whilst fertile seeds are produced by the concourse of the two sexual elements. The modifications which arise through bud-variation can generally be propagated to any extent by grafting, budding, cuttings, bulbs, &c., and occasionally even by seed. ”

“ From the various facts now given there can be no doubt that the same individual plant, whether a hybrid or a mongrel, sometimes returns in its leaves, flowers, and fruit, either wholly or by segments, to both parent-forms, in the same manner as the Cytisus adami, and the Bizzarria Orange.
We will now consider the few facts which have been recorded in support of the belief that a variety when grafted or budded on another variety sometimes affects the whole stock, or at the point of junction gives rise to a bud, or graft-hybrid, which partakes of the characters of both stock and scion. ”

“ I have now shown, on the authority of several excellent observers, in the case of plants belonging to widely different orders, that the pollen of one species or variety, when applied to a distinct form, occasionally causes the coats of the seeds and the ovarium or fruit, including even in one instance the calyx and upper part of the peduncle of the mother-plant, to become modified. Sometimes the whole of the ovarium or all the seeds are thus affected ”

“ We have seen that varieties produced from seeds and from buds resemble each other so closely in general appearance, that they cannot possibly be distinguished. Just as certain species and groups of species, when propagated by seed, are more variable than other species or genera, so it is in the case of certain bud-varieties. Thus the Queen of England Chrysanthemum has produced by this latter process no less than six, and Rollisson's Unique Pelargonium four distinct varieties ”

“ There is ample evidence, as we have just seen, that the male element may either directly affect the structure of the female, or in the case of animals lead to the modification of her offspring. There is a considerable but insufficient body of evidence showing that the tissues of two plants may unite and form a bud having a blended character; or again, that buds inserted into a stock may affect all the buds subsequently produced by this stock. Two embryos, differing from each other and contained in the same seed, may cohere and form a single plant. ”

“ 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 resemblance, or rather identity, is rendered far more striking if the facts can be trusted which apparently render it probable that the cellular tissue of one species or variety, when budded or grafted on another, may give rise to a bud having an intermediate character. In this chapter we clearly see that variability is not necessarily contingent on sexual generation, though much more frequently its concomitant than on bud-reproduction. ”

“ When the tendency to reversion affects many buds on the same tree, it becomes covered with different kinds of leaves, flowers, or fruit; but there is reason to believe that such fluctuating varieties have generally arisen from seed. It is well known that, out of a number of seedling varieties, some transmit their character much more truly by seed than others; so with bud-varieties some retain their character by successive buds more truly than others ”

“ I may premise that with plants the ovarium and the coats of the ovules are obviously parts of the female, and it could not have been anticipated that they would be affected by the pollen of a foreign variety or species, although the development of the embryo, within the embryonic sack, within the ovule, within the ovarium, of course depends on the male element. ”

“ Although I have been able to collect a good many cases of bud-variation, as shown in the previous lists, and might probably, by searching foreign horticultural works, have collected more cases, yet their total number is as nothing in comparison with that of seminal varieties. With seedlings raised from the more variable cultivated plants, the variations are almost infinitely numerous, but their differences are generally slight: only at long intervals of time a strongly marked modification appears. ”

“ When, however, the later flowers or fruit, produced during the same season or during a succeeding year or generation, become striped or half-in-half, &c., the segregation of the two colours is strictly a case of reversion by bud-variation. In a future chapter I shall show that, with animals of crossed parentage, the same individual has been known to change its character during growth, and to revert to one of its parents which it did not at first resemble. ”

“ It deserves notice that all the plants which have yielded bud-variations have likewise varied greatly by seed.
These plants belong to so many orders that we may infer that almost every plant would be liable to bud-variation if placed under the proper exciting conditions. These conditions, as far as we can judge, mainly depend on long-continued and high cultivation; for almost all the plants in the foregoing lists are perennials, and have been largely propagated in many soils and under different climates, by cuttings, offsets, bulbs, tubers, and especially by budding or grafting. ”

“ These various facts ought to be well considered by any one who wishes to embrace under a single point of view the various modes of reproduction by gemmation, division, and sexual union, the reparation of lost parts, variation, inheritance, reversion, and other such phenomena. ”

“ 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 ”

“ 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. ”

“ But if we turn to the other end of the series, namely, to such cases as that of a peach-tree which, after having been cultivated by tens of thousands during many years in many countries, and after having annually produced thousands of buds, all of which have apparently been exposed to precisely the same conditions, yet at last suddenly produces a single bud with its whole character greatly transformed, we are driven to an opposite conclusion. ”

“ Rivers has found that moss-roses generally reproduce themselves by seed; and the mossy character has been transferred by crossing, from one species of rose to another. The Boston nectarine, which appeared as a bud-variation, produced by seed a closely allied nectarine. We have however seen, on the authority of Mr. Salter, that seed taken from a branch with leaves variegated through bud-variation, transmits this character very feebly; whilst many plants, which became variegated as seedlings, transmit variegation to a large proportion of their progeny. ”

“ 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. [61] 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. [62] There have been endless disputes whether variegation should be considered as a disease. ”

“ According to Sir R. Schomburgk, plants from the warmer temperate regions, when cultivated under the hot climate of St. Domingo, are eminently liable to bud-variation; but change of climate is by no means a necessary contingent, as we see with the gooseberry, currant, and some others. Plants living under their natural conditions are very rarely subject to bud-variation: variegated and coloured leaves have, however, been occasionally observed ”

“ 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. ”

“ 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. ”

“ Valery apple, which, from the abortion of the stamens, does not produce pollen, but, being annually fertilised by the girls of the neighbourhood with pollen of many kinds, bears fruit, "differing from each other in size, flavour, and colour, but resembling in character the hermaphrodite kinds by which they have been fertilised." ”

“ 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. ”

“ In illustration of the origin of Cytisus adami, several cases were given of partial or complete reversion, both with hybrid and mongrel plants; hence we may suspect that the strong tendency in the Chrysanthemum, for instance, to produce by bud-variation differently-coloured flowers, results from the varieties formerly having been intentionally or accidentally crossed; and that their descendants at the present day still occasionally revert by buds to the colours of the more persistent parent-varieties. This is almost certainly the case with Rollisson's Unique Pelargonium ”

“ 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. [1] 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." ”

“ Henry fertilised Arabis blepharophylla with pollen of A. Soyeri, and the pods thus produced, of which he was so kind as to send me detailed measurements and sketches, were much larger in all their dimensions than those naturally produced by either the male or female parent-species. In a future chapter we shall see that the organs of vegetation in hybrid plants, independently of the character of either parent, are sometimes developed to a monstrous size ”

“ 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. ”

“ 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. ”