Inhorticulture, agraft-chimaera may arise ingrafting at the point of contact betweenrootstock andscion and will have properties intermediate between those of its "parents". Unlikegraft hybrids, a graft-chimaera is not a truehybrid but a mixture of cells, each with thegenotype of one of its "parents": it is achimaera. Hence, the once widely used term "graft-hybrid" is inaccurate for a graft-chimaera.
Propagation is bycloning only. In practice graft-chimaeras are not noted for their stability and may easily revert to one of the "parents".
Article 21 of theICNCP stipulates that a graft-chimaera can be indicated either by
a formula: the names of both "parents", in alphabetical order, joined by theplus sign "+":
Crataegus +Mespilus
a name:
if the "parents" belong to differentgenera a name may be formed by joining part of onegeneric name to the whole of the other generic name. This name must not be identical to a generic name published under theInternational Code of Nomenclature for algae, fungi, and plants (ICN). For example+Crataegomespilus is the name for the graft-chimaera which may also be indicated by the formulaCrataegus +Mespilus. This name is clearly different from ×Crataemespilus, the name under theICN for the true hybrid betweenCrataegus andMespilus, which can also be designated by the formulaCrataegus ×Mespilus.[a]
if both "parents" belong to the same genus the graft-chimaera may be given acultivar name. For exampleSyringa 'Correlata' is a graft-chimaera involvingSyringa vulgaris (common lilac) andSyringa × chinensis (Rouen lilac, which is itself a hybrid betweenS. vulgaris andS. persica). No plus sign is used, because both "parents" belong to the genusSyringa.
A graft-chimaera cannot have aspecies name, because it is simultaneously two species. Although +Laburnocytisus 'Adamii', for example, is sometimes seen written as if it were a species (+Laburnocytisus adamii), this is incorrect.[citation needed]
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 ofCytisus 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.
