BUD-VARIATION BY SUCKERS, TUBERS, AND BULBS.
All the cases. .h.i.therto 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 (11/70. M. Lemoine quoted in "Gardener"s Chronicle" 1867 page 74 has lately observed that the Symphytum with variegated leaves cannot be propagated by division of the roots. He also found that out of 500 plants of a Phlox with striped flowers, which had been propagated by root-division, only seven or eight produced striped flowers. See also on striped Pelargoniums "Gardener"s Chronicle" 1867 page 1000.); 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 a.n.a.logous 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. (11/71. Anderson "Recreations in Agriculture" volume 5 page 152.) My father repeatedly tried this experiment, and always with the same result. I may here mention that maize and wheat sometimes produce new varieties from the stock or root, as does the sugar-cane. (11/72. For wheat see "Improvement of the Cereals" by P. Shirreff 1873 page 47. For maize and sugar-cane Carriere ibid pages 40, 42. With respect to the sugar-cane Mr.
J. Caldwell of Mauritius says ("Gardener"s Chronicle" 1874 page 316) the Ribbon cane has here "sported into a perfectly green cane and a perfectly red cane from the same head. I verified this myself, and saw at least 200 instances in the same plantation, and the fact has completely upset all our preconceived ideas of the difference of colour being permanent. The conversion of a striped cane into a green cane was not uncommon, but the change into a red cane universally disbelieved, and that both events should occur in the same plant incredible. I find, however, in Fleischman"s "Report on Sugar Cultivation in Louisiana for 1848 by the American Patent Office, the circ.u.mstance is mentioned, but he says he never saw it himself.")
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 circ.u.mstance, all the eyes in a tuber vary in the same manner and at the same time, so that the whole tuber a.s.sumes a new character. For instance, a single eye in a tuber of the old FORTY-FOLD POTATO, which is a purple variety, was observed (11/73.
"Gardener"s Chronicle" 1857 page 662.) 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. (11/74. "Gard. Chronicle" 1841 page 814.) 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. (11/75. Ibid 1857 page 613.) Several cases have been recorded of large portions of whole rows of potatoes slightly changing their character. (11/76. Ibid 1857 page 679. See also Philips "Hist. of Vegetables" volume 2 page 91 for other and similar accounts.)
Dahlias propagated by tubers under the hot climate of St. Domingo vary much; Sir R. Schomburgk gives the case of the "b.u.t.terfly 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." (11/77.
"Journal of Proc. Linn. Soc." volume 2 Botany page 132.) 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." (11/78. Loudon"s "Gardener"s Mag." volume 8 1832 page 94.) Another case is described of a dahlia with purple flowers which bore a white flower streaked with purple. (11/79. "Gard. Chronicle" 1850 page 536; and 1842 page 729.)
Considering how long and extensively many Bulbous plants have been cultivated, and how numerous are the varieties produced from seed, these plants have not perhaps varied so much by offsets,--that is, by the production of new bulbs,--as might have been expected. With the Hyacinth, however, several instances have been given by M. Carriere. A case also has been recorded of a blue variety which for three successive years gave offsets producing white flowers with a red centre. (11/80. "Des Jacinthes"
etc. Amsterdam 1768 page 122.) Another hyacinth bore (11/81. "Gardener"s Chronicle" 1845 page 212.) on the same truss a perfectly pink and a perfectly blue flower. I have seen a bulb producing at the same time one stalk or truss with fine blue flowers, another with fine red flowers, and a third with blue flowers on one side and red on the other; several of the flowers being also longitudinally striped red and blue.
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." (11/82. Loudon"s "Encyclopaedia of Gardening" page 1024.) The 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 (11/83. "Production des Varietes" 1865 p. 63.) 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.
d.i.c.kson maintains (11/84. "Gardener"s Chronicle" 1841 page 782; 1842 page 55.) 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. Iris xiphium, according to M. Carriere (page 65), behaves in nearly the same manner, as do so many tulips.
During two consecutive years all the early flowers in a bed of Tigridia conchiflora (11/85. "Gardener"s Chron." 1849 page 565.) resembled those of the old T. pavonia; but the later flowers a.s.sumed their proper colour of fine yellow, spotted with crimson. An apparently authentic account has been published (11/86. "Transact. Lin. Soc." volume 2 page 354.) 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 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 cla.s.sed 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 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. With the potato, we have seen an intermediate case, for all the eyes in one tuber 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. (11/87. G.o.dron "De l"Espece"
tome 2 page 84.) 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 (11/88. M. Carriere has lately described in the "Revue Horticole" December 1, 1866 page 457, an extraordinary case. He twice inserted grafts of the Aria vest.i.ta on thorn- trees (epines) growing in pots; and the grafts, as they grew, produced shoots with bark, buds, leaves, petioles, petals, and flower-stalks, all widely different from those of the Aria. The grafted shoots were also much hardier, and flowered earlier, than those on the ungrafted Aria.) were considered by Andrew Knight (11/89. "Transact. Hort. Soc." volume 2 page 160.) 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 a.s.sumed 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, whilst they closely resemble each other in old age; and as with certain oaks, and with some varieties of the lime and hawthorn. (11/90. For the cases of oaks see Alph. De Candolle in "Bibl. Univers." Geneva November 1862; for limes etc.
Loudon"s "Gard. Mag." volume 11 1835 page 503.)]
GRAFT-HYBRIDS.
Before giving a summary on Bud-variation I will discuss some singular and anomalous cases, which are more or less closely related to this same subject. I will begin with the famous case of Adam"s laburnum or Cytisus adami, a form or hybrid intermediate between two very distinct species, namely, C. laburnum and purpureus, the common and purple laburnum; but as this tree has often been described, I will be as brief as I can.
[Throughout Europe, in different soils and under different climates, branches on this tree have repeatedly and suddenly reverted to the two 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 narrow bright yellow 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. (11/91. For a.n.a.logous facts see Braun "Rejuvenescence" in "Ray Soc. Bot. Mem." 1853 page 320; and "Gardener"s Chronicle" 1842 page 397; also Braun in "Sitzungsberichte der Ges.
naturforschender Freunde" June 1873 page 63.) 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 larger number. Two seedlings raised by Mr. Herbert from such seed (11/92.
"Journal of Hort. Soc." volume 2 1847 page 100.) 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 hybridised 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 mult.i.tude 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 grains. Although the pollen of the reverted purple flowers was in so poor a condition, the ovules were well formed, and the seeds, when mature, germinated freely with me. Mr. Herbert raised plants from seeds of the reverted purple flowers, and they differed a VERY LITTLE from the usual state of C. purpureus. Some which I raised in the same manner did not differ at all, either in the character of their flowers or of the whole bush, from the pure C. purpureus. Prof. Caspary has examined the ovules of the dingy-red and sterile flowers in several plants of C. adami on the Continent (11/93. See "Transact. of Hort. Congress of Amsterdam" 1865; but I owe most of the following information to Prof. Caspary"s letters.) 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 observation (11/94. "Nouvelles Archives du Museum" tome 1 page 143.) 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 (11/95. See on this head Naudin ibid page 141.), 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. The whole case has been attributed by some authors to 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 embryos differing in their characters may be developed within the same seed and cohere; and it has been supposed that C. adami thus originated.
Many botanists 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 not of much value; but Reisseck, Caspary, and 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 supported by the fact that such hybrids have arisen in this genus. 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. (11/96. Braun in "Bot.
Mem. Ray. Soc." 1853 page 23.) Thus, also, Waterer"s laburnum, the C.
alpino-laburnum (11/97. This hybrid has never been described. It is exactly intermediate in foliage, time of flowering, dark striae at the base of the standard petal, hairiness of the ovarium, and in almost every other character, between C. laburnum and alpinus; but it approaches the former species more nearly in colour, and exceeds it in the length of the racemes.
We have before seen that 20.3 per cent of its pollen-grains are ill-formed and worthless. My plant, though growing not above thirty or forty yards from both parent-species, during some seasons yielded no good seeds; but in 1866 it was unusually fertile, and its long racemes produced from one to occasionally even four pods. Many of the pods contained no good seeds, but generally they contained a single apparently good seed, sometimes two, and in one case three seeds. Some of these seeds germinated, and I raised two trees from them; one resembles the present form; the other has a remarkable dwarf character with small leaves, but has not yet flowered.) 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 to Poiteau (11/98. "Annales de la Soc. de l"Hort. de Paris" tome 7 1830 page 93.) by M. Adam, who raised the plant, showing that C. adami is not an ordinary hybrid; but is what may be called a graft-hybrid, that is, one produced from the united cellular tissue of two distinct species. 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. (11/99. An account was given in the "Gardener"s Chronicle" 1857 pages 382, 400, of a common laburnum on which grafts of C. purpureus had been inserted, and which gradually a.s.sumed the character of C. adami; but I have little doubt that C. adami had been sold to the purchaser, who was not a botanist, in the place of C. purpureus. I have ascertained that this occurred in another instance.) 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.]
I will therefore give all the facts which I have been able to collect on the formation of hybrids between distinct species or varieties, without the intervention of the s.e.xual organs. For if, as I am now convinced, this is possible, it is a most important fact, which will sooner or later change the views held by physiologists with respect to s.e.xual reproduction. A sufficient body of facts will afterwards be adduced, showing that the segregation or separation of the characters of the two parent-forms by bud- variation, as in the case of Cytisus adami, is not an unusual though a striking phenomenon. We shall further see that a whole bud may thus revert, or only half, or some smaller segment.
[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 (11/100. Gallesio "Gli Agrumi dei Giard. Bot. Agrar. di. Firenze" 1839 page 11. In his "Traite du Citrus" 1811 page 146, he speaks as if the compound fruit consisted in part of a lemon, but this apparently was a mistake.), 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 (11/101. "Gardener"s Chron." 1855 page 628. See also Prof. Caspary in "Transact. Hort. Congress of Amsterdam" 1865.) resembles in its general nature the bizzarria, and differs only in the orange being of the sweet kind; this and the citron are blended together in the same fruit, or are 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 that the species in this genus often cross spontaneously.
It is notorious that when the variegated Jessamine is budded on the common kind, the stock sometimes produces buds bearing variegated leaves: Mr.
Rivers, as he informs me, has seen instances of this. The same thing occurs with the Oleander. (11/102. Gartner "b.a.s.t.a.r.derzeugung" s. 611 gives many references on this subject.) Mr. Rivers, on the authority of a trustworthy friend, states that some buds of a golden-variegated ash, which were inserted into common ashes, all died except one; but the ash-stocks were affected (11/103. A nearly similar account was given by Brabley in 1724 in his "Treatise on Husbandry" volume 1 page 199.) and produced, both above and below the points of insertion of the plates of bark bearing the dead buds, shoots which bore variegated leaves. Mr. J. Anderson Henry has communicated to me a nearly similar case: Mr. Brown, of Perth, observed many years ago, in a Highland glen, an ash-tree with yellow leaves; and buds taken from this tree were inserted into common ashes, which in consequence were affected, and produced the Blotched Breadalbane Ash. This variety has been propagated, and has preserved its character during the last fifty years. Weeping ashes, also, were budded on the affected stocks, and became similarly variegated. It has been repeatedly proved that several species of Abutilon, on which the variegated A. thompsonii has been grafted, become variegated. (11/104. Morren "Bull. de l"Acad. R. des Sciences de Belgique" 2de series tome 28 1869 page 434. Also Magnus "Gesellschaft naturforschender Freunde, Berlin" February 21, 1871 page 13; ibid June 21, 1870 and October 17, 1871. Also "Bot. Zeitung" February 24, 1871.)
Many authors consider variegation as the result of disease; and the foregoing cases may be looked at as the direct result of the inoculation of a disease or some weakness. This has been almost proved to be the case by Morren in the excellent paper just referred to, who shows that even a leaf inserted by its footstalk into the bark of the stock is sufficient to communicate variegation to it, though the leaf soon perishes. Even fully formed leaves on the stock of Abutilon are sometimes affected by the graft and become variegated. Variegation is much influenced, as we shall hereafter see, by the nature of the soil in which the plants are grown; and it does not seem improbable that whatever change in the sap or tissues certain soils induce, whether or not called a disease, might spread from the inserted piece of bark to the stock. But a change of this kind cannot be considered to be of the nature of a graft-hybrid.
There is a variety of the hazel with dark-purple leaves, like those of the copper-beech: no one has attributed this colour to disease, and it apparently is only an exaggeration of a tint which may often be seen on the leaves of the common hazel. When this variety is grafted on the common hazel (11/105. Loudon"s "Arboretum" volume 4 page 2595.), it sometimes colours, as has been a.s.serted, the leaves below the graft; although negative evidence is not of much value, I may add that Mr. Rivers, who has possessed hundreds of such grafted trees, has never seen an instance.
Gartner (11/106. "b.a.s.t.a.r.derzeugung" s. 619.) quotes two separate accounts of branches of dark and white-fruited vines which had been united in various ways, such as being split longitudinally, and then joined, etc.; and these branches produced distinct bunches of grapes of the two colours, and other bunches with berries, either striped, or of an intermediate and new tint. Even the leaves in one case were variegated. These facts are the more remarkable because Andrew Knight never succeeded in raising variegated grapes by fertilising white kinds by pollen of dark kinds; though, as we have seen, he obtained seedlings with variegated fruits and leaves, by fertilising a white variety by the already variegated dark Aleppo grape.
Gartner attributes the above-quoted cases merely to bud-variation; but it is a strange coincidence that the branches which had been grafted in a peculiar manner should alone thus have varied; and H. Adorne de Tscharner positively a.s.serts that he produced the described result more than once, and could do so at will, by splitting and uniting the branches in the manner described by him.
I should not have quoted the following case had not the author of "Des Jacinthes" (11/107. Amsterdam 1768 page 124.) impressed me with the belief not only of his extensive knowledge, but of his truthfulness: he 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 I have myself 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, which makes the case closely a.n.a.logous with that of the blended colours of the grapes on the united vine branches.
In the case of roses it is supposed that several graft-hybrids have been formed, but there is much doubt about these cases, owing to the frequency of ordinary bud-variations. The most trustworthy instance known to me is one, recorded by Mr. Poynter (11/108. "Gardener"s Chron." 1860 page 672 with a woodcut.) who a.s.sures me in a letter of the entire accuracy of the statement. Rosa devoniensis had been budded some years previously on a white Banksian rose; and from the much enlarged point of junction, whence the Devoniensis and Banksian still continued to grow, a third branch issued, which was neither pure Banksian nor pure Devoniensis, but partook of the character of both; the flowers resembled, but were superior in character to those of the variety called Lamarque (one of the Noisettes), while the shoots were similar in their manner of growth to those of the Banksian rose, with the exception that the longer and more robust shoots were furnished with p.r.i.c.kles. This rose was exhibited before the Floral Committee of the Horticultural Society of London. Dr. Lindley examined it and concluded that it had certainly been produced by the mingling of R.
banksiae with some rose like R. devoniensis, "for while it was very greatly increased in vigour and in size of all the parts, the leaves were half-way between a Banksian and Tea-scented rose." It appears that rose-growers were previously aware that the Banksian rose sometimes affects other roses. As Mr. Poynter"s new variety is intermediate in its fruit and foliage between the stock and scion, and as it arose from the point of junction between the two, it is very improbable that it owes its origin to mere bud-variation, independently of the mutual influence of the stock and scion.
Lastly, with respect to potatoes. Mr. R. Trail stated in 1867 before the Botanical Society of Edinburgh (and has since given me fuller information), that several years ago he cut about sixty blue and white potatoes into halves through the eyes or buds, and then carefully joined them, destroying at the same time the other eyes. Some of these united tubers produced white, and others blue tubers; some, however, produced tubers partly white and partly blue; and the tubers from about four or five were regularly mottled with the two colours. In these latter cases we may conclude that a stem had been formed by the union of the bisected buds, that is, by graft- hybridisation.
In the "Botanische Zeitung" (May 16, 1868), Professor Hildebrand gives an account with a coloured figure, of his experiments on two varieties which were found during the same season to be constant in character, namely, a somewhat elongated rough-skinned red potato and a rounded smooth white one.
He inserted buds reciprocally into both kinds, destroying the other buds.
He thus raised two plants, and each of these produced a tuber intermediate in character between the two parent-forms. That from the red bud grafted into the white tuber, was at one end red and rough, as the whole tuber ought to have been if not affected; in the middle it was smooth with red stripes, and at the other end smooth and altogether white like that of the stock.
Mr. Taylor, who had received several accounts of potatoes having been grafted by wedge-shaped pieces of one variety inserted into another, though sceptical on the subject, made twenty-four experiments which he described in detail before the Horticultural Society. (11/109. "Gardener"s Chronicle"
1869 page 220.) He thus raised many new varieties, some like the graft or like the stock; others having an intermediate character. Several persons witnessed the digging up of the tubers from these graft-hybrids; and one of them, Mr. Jameson, a large dealer in potatoes, writes thus, "They were such a mixed lot, as I have never before or since seen. They were of all colours and shapes, some very ugly and some very handsome." Another witness says "some were round, some kidney, pink-eyed kidney, piebald, and mottled red and purple, of all shapes and sizes." Some of these varieties have been found valuable, and have been extensively propagated. Mr. Jameson took away a large piebald potato which he cut into five sets and propagated; these yielded round, white, red, and piebald potatoes.
Mr. Fitzpatrick followed a different plan (11/110. "Gard. Chronicle" 1869 page 335.); he grafted together not the tubers but the young stems of varieties producing black, white, and red potatoes. The tubers borne by three of these twin or united plants were coloured in an extraordinary manner; one was almost exactly half black and half white, so that some persons on seeing it thought that two potatoes had been divided and rejoined; other tubers were half red and half white, or curiously mottled with red and white, or with red and black, according to the colours of the graft and stock.
The testimony of Mr. Fenn is of much value, as he is "a well known potato- grower" who has raised many new varieties by crossing different kinds in the ordinary manner. He considers it "demonstrated" that new, intermediate varieties can be produced by grafting the tubers, though he doubts whether such will prove valuable. (11/111. "Gardener"s Chronicle" 1869 page 1018 with remarks by Dr. Masters on the adhesion of the united wedges. See also ibid 1870 pages 1277, 1283.) He made many trials and laid the results, exhibiting specimens, before the Horticultural Society. Not only were the tubers affected, some being smooth and white at one end and rough and red at the other, but the stems and leaves were modified in their manner of growth, colour and precocity. Some of these graft-hybrids after being propagated for three years still showed in their haulms their new character, different from that of the kind from which the eyes had been taken. Mr. Fenn gave twelve of the tubers of the third generation to Mr.
Alex. Dean, who grew them, and was thus converted into a believer in graft- hybridisation, having previously been a complete sceptic. For comparison he planted the pure parent-forms alongside the twelve tubers; and found that many of the plants from the latter (11/112. "Gard. Chronicle" 1871 page 837.) were intermediate between the two parent-forms in precocity, in the tallness, uprightness, jointing, and robustness of the stems, and in the size and colour of the leaves.
Another experimentalist, Mr. Rintoul, grafted no less than fifty-nine tubers, which differed in shape (some being kidneys) in smoothness and colour (11/113. "Gardener"s Chronicle" 1870 page 1506.) and many of the plants thus raised "were intermediate in the tubers as well as in the haulms." He describes the more striking cases.
In 1871 I received a letter from Mr. Merrick, of Boston, U.S.A., who states that, "Mr. Fearing Burr, a very careful experimenter and author of a much valued book, "The Garden Vegetables of America" has succeeded in producing distinctly mottled and most curious potatoes--evidently graft-hybrids, by inserting eyes from blue or red potatoes into the substance of white ones, after removing the eyes of the latter. I have seen the potatoes, and they are very curious."
We will now turn to the experiments made in Germany, since the publication of Prof. Hildebrand"s paper. Herr Magnus relates (11/114. "Sitzungsberichte der Gesellschaft naturforschender Freunde zu Berlin" October 17, 1871.) the results of numerous trials made by Herren Reuter and Lindemuth, both attached to the Royal Gardens of Berlin. They inserted the eyes of red potatoes into white ones, and vice versa. Many different forms partaking of the characters of the inserted bud and of the stock were thus obtained; for instance, some of the tubers were white with red eyes.
Herr Magnus also exhibited in the following year before the same Society (November 19, 1872), the produce of grafts between black, white, and red potatoes, made by Dr. Neubert. These were made by uniting not the tubers but the young stems, as was done by Mr. Fitzpatrick. The result was remarkable, inasmuch as all the tubers thus produced were intermediate in character, though in a variable degree. Those between the black and the white or the red were the most striking in appearance. Some from between the white and red had one half of one colour and the other half of the other colour.
At the next meeting of the society Herr Magnus communicated the results of Dr. Heimann"s experiments in grafting together the tubers of red Saxon, blue, and elongated white potatoes. The eyes were removed by a cylindrical instrument, and inserted into corresponding holes in other varieties. The plants thus produced yielded a great number of tubers, which were intermediate between the two parent-forms in shape, and in the colour both of the flesh and skin.
Herr Reuter experimented (11/115. Ibid November 17, 1874. See also excellent remarks by Herr Magnus.) by inserting wedges of the elongated White Mexican potato into a Black Kidney potato. Both sorts are known to be very constant, and differ much not only in form and colour, but in the eyes of the Black Kidney being deeply sunk, whereas those of the White Mexican are superficial and of a different shape. The tubers produced by these hybrids were intermediate in colour and form; and some which resembled in form the graft, i.e. the Mexican, had eyes deeply sunk and of the same shape as in the stock or Black Kidney.]
Any one who will attentively consider the abstract now given, of the experiments made by many observers in several countries, will, I think, be convinced that by grafting two varieties of the potato together in various ways, hybridised plants can be produced. It should be observed that several of the experimentalists are scientific horticulturists, and some of them potato-growers on a large scale, who, though beforehand sceptical, have been fully convinced of the possibility, even of the ease, of making graft- hybrids. The only way of escaping from this conclusion is to attribute all the many recorded cases to simple bud-variation. Undoubtedly the potato, as we have seen in this chapter, does sometimes, though not often, vary by buds; but it should be especially noted that it is experienced potato- growers, whose business it is to look out for new varieties, who have expressed unbounded astonishment at the number of new forms produced by graft-hybridisation. It may be argued that it is merely the operation of grafting, and not the union of two kinds, which causes so extraordinary an amount of bud-variation; but this objection is at once answered by the fact that potatoes are habitually propagated by the tubers being cut into pieces, and the sole difference in the case of graft-hybrids is that either a half or a smaller segment or a cylinder is placed in close opposition with the tissue of another variety. Moreover, in two cases, the young stems were grafted together, and the plants thus united yielded the same results as when the tubers were united. It is an argument of the greatest weight that when varieties are produced by simple bud-variation, they frequently present quite new characters; whereas in all the numerous cases above given, as Herr Magnus likewise insists, the graft-hybrids are intermediate in character between the two forms employed. That such a result should follow if the one kind did not affect the other is incredible.