The Names Of Plants.pdf

also in our own horticultural literature (Bagust, 2001), as a shorthand cross-reference.
Thus, Narcissus bulbocodium subsp. bulbocodium var. conspicuus is written as
Narcissus bulbocodium bulbocodium conspicuus. This is confusing when the cultivar
name has a Latin form since this then has the appearance of a pre-Linneaen phrase
name (e.g. Narcissus albus plenus odoratus and Rosa sericea omeiensis praecox).
Graft chimaeras
The International Code of Nomenclature for Cultivated Plants
One group of plants which is entirely within the province of gardening and the
Cultivated Code is that of the graft chimaeras, or graft hybrids. These are plants in
which a mosaic of tissues from the two parents (not closely related) in a grafting
partnership results in an individual plant upon which shoots resembling each of the
parents, and in some cases shoots of intermediate character, are produced in an
unpredictable manner. The closest analogy amongst animals is the experimental
rodent on which a human ear is being grown, or the human into which a heart valve
has been grafted from a genetically manipulated pig.
Unlike sexually produced hybrids, the admixture of the two parents’ contributions
is not at the level of the nucleus in each and every cell but is more like a marbling
of a ground tissue of one parent with streaks of tissue of the other parent.
Chimaeras can also result from mutation in a growing point, from which organs are
formed composed of normal and mutant tissues – as with genetic forms of variegation.
In all cases, three categories may be recognized in terms of the extent of tissue
‘marbling’, called sectorial, mericlinal and periclinal chimaeras. The chimaeral condition
is denoted by the addition sign ‘+’ instead of the multiplication sign ‘’ used
for true hybrids. A chimaera which is still fairly common in Britain is that named
Laburnocytisus adamii C. K. Schneider. This was the result of a graft between
Cytisus purpureus Scop. and Cytisus laburnum L., which are now known as
Chamaecytisus purpureus (Scop.) Link and Laburnum anagyroides Medicus, respectively.
Although its former name Cytisus adamii would not now be correct, the
name Laburnocytisus meets the requirement of combining substantial parts of the
two parental generic names, and can stand.
Combining generic names for graft chimaeras must not duplicate a composite
name for a sexually produced hybrid between the same progenitors. Hybrids
between species of Crataegus and species of Mespilus are Crataemespilus but the chimaera
between the same species of the same genera is Crataegomespilus. As in this
example, the same progenitors may yield distinctive chimaeras and these may be
given cultivar names: Crataegomespilus ‘Dardarii’ and Crataegomespilus ‘Jules
d’Asnières’.
It is interesting to speculate that if cell- and callus-culture techniques could be
used to produce chimaeral mixtures to order, it may be possible to create some of
the conditions which were to have brought about the early ‘green revolutions’ of the
1950–2000 period. Protoplast fusion methods failed to combine the culturally and
economically desirable features of distant parents, which were to have given multicrop
plants and new nitrogen-fixing plants, because of the irregularities in fusion of
both protoplasts and their nuclei. It may be that intact cells would prove easier to
admix. However, molecular genetics and genetic manipulation have shown that
genetic control systems can be modified in ways which suggest that any aspect of a
plant can, potentially, be manipulated to suit man’s requirements and novel genetic
traits can be inserted into a plant’s genome by using DNA implants. The genetically
modified (GM) results of such manipulation are the products of commercial undertakings,
and may be given cultivar names, but are protected commercially by trade
designations.
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