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 assumed 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 sexual 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 sexual 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.