There
are two types of names that are applied to every useful plant: common names and
scientific names. Common names are those that are used in ordinary
conversation, and are in a vernacular language (e.g., wheat, apple, dandelion).
These are convenient enough for most purposes, but can create confusion. Many
plants have multiple common names, e.g., Chenopodium
album can be called goosefoot, fat-hen, lamb’s quarters, or pigweed in
different parts of North America. Moreover, the same common name may be used
for different plants in different places: pigweed sometimes refers to species
of Amaranthus, another edible weed. To
minimize this problem, American commercial products are required to use
“standardized common names.” The American Herbal Product Association’s book Herbs of Commerce, 2nd ed.
(McGuffin et al., 2000) provides an extensive list of marketed species and
specifies for each the preferred common name (which in some cases is the
scientific name or a portion of it). However, many of their choices are not
exclusively used in ordinary English. For example, although the name “Siberian
ginseng” for Eleutherococcus senticosus
has been specifically outlawed in commercial speech, it is still the common
name most used by laymen. Then there is the question of scientific or
commercial communication with people who speak different languages. And, of
course, there are many foreign plants that have no common names in English. A
scientific or Latin name is intended to provide a name for a plant that is
“always correct” and can be used to communicate about that species among
botanists worldwide, no matter what language they speak.
A
full scientific name has three parts, in the form Genus epithet Auth.: the genus in which the plant is placed, the
specific epithet, and an abbreviation of the name of the “authority” who first
published that species in scientific literature. Binomial or Linnaean
nomenclature requires that each species belong to a genus (plural: genera), a
group of closely related plants, such as Echinacea
or Panax. The species within each
genus are denoted by specific epithets, which often refer to the plant’s
appearance, origins or uses, e.g., angustifolia,
narrow-leaved; africana, from Africa;
officinale, of the shops (often used
for medicinal plants). The species name includes both the genus and specific
epithet, such as Echinacea angustifolia,
and is printed in italics because it is in Latin or Latinized. The ending of
the specific epithet is in the form of a Latin adjective, and changes depending
upon the Latin gender of the genus. (In an homage to classical tradition, the
name of a tree is traditionally treated as feminine no matter what its apparent
gender.) After the first mention in a text, the genus is often abbreviated
(except at the beginning of a sentence, where it should be spelled out), and
the authority is always omitted, e.g., E.
angustifolia. The reason for including the authority at first mention is
that sometimes the same name has been used by two authors to refer to two
different species, and providing the authority leaves no doubt which one is
meant. The names of older authorities who published thousands of names are
sometimes highly abbreviated, e.g. “L.” for Linnaeus. Sometimes the authority
is of the form “Smith ex Jones,” which indicates that Jones actually published
the name, but gave Smith credit as the authority responsible for the new
species.
Most
hybrid plants are not given formal names, but are described by their parentage,
e.g. “Salix alba L. ×S. nigra Marsh.” If a particular hybrid
is common and morphologically consistent, especially if it is reproductively
isolated from its parents, it may be given a species name with an × before the
specific epithet to indicate that it originated as a cross between two other
species. This symbol may be added after a species has been described if it is
later determined to be of hybrid origin, e.g., Mentha ×piperita L.
In
the early days of botany, it was common for multiple names to be published for
a single species, especially one that is found in many places or that is
variable enough to be mistaken for a group of several species. These excess
names are called synonyms. To reduce confusion, there should be only one
correct name for a species under a given taxonomic treatment. The International
Code of Botanical Nomenclature provides rules to determine what that correct
name is. These rules are too complicated to recount in detail, but the
principle of priority usually applies. That is, the oldest name that was
“validly and legitimately” published for a species provides the specific
epithet that should be used if possible. Certain errors in the publication of a
name can make it invalid or illegitimate, meaning that it should not be used no
matter what its age. (For example, if you publish a new name that had already
been used by someone else, your name will be illegitimate.) If the strict
application of these rules would lead to great nomenclatural confusion, there
are procedures by which younger names can be conserved or older names rejected
at the meetings of the International Botanical Congress, which are held every
six years.
A
particular issue to note is that the determination of the “correct name” only
applies to a specified taxonomic treatment, and that under different
treatments, a different name may be correct. Outside the botanical community,
people often assume that species and even genera are groups that have a
definite, objective biological meaning. This, perhaps, is because the mammals
with which they are most familiar are easily distinguished and genetically
separated from related species. In variable or freely hybridizing groups of
plants, it is not always clear how many species should be recognized. The
boundaries of species described in the literature are often someone’s taxonomic
opinion rather than a hard fact, and other authors may choose to recognize more
or fewer species in a group. The term “genus” has no real biological meaning at
all. It is simply a group of closely related species that are recognized as
such by being given the same name, often because they are similar enough to be
recognized by their shared features. In modern taxonomic practice, it is
desirable for genera to be natural groups, which comprise all of the
descendants of some common ancestor, but the size of these groups is arbitrary.
Where one taxonomist chooses to recognize one large genus, another might break
that genus into half a dozen smaller genera. The same applies to the grouping
of genera into families.
As
for nomenclature, when a species is transferred from one genus to another, a
new species name must be created for it. This name ordinarily uses the original
specific epithet, with the original authority’s name or abbreviation in
parentheses before that of the new authority. For example, black cohosh was
described by Linnaeus as Actaea racemosa
L.; later taxonomists chose to split Actaea
into two genera, and the name Cimicifuga
racemosa (L.) Nutt. was published by Nuttall for the same species. Each of
these names is a synonym for the other, and A.
racemosa is also the “basionym” of C.
racemosa, or the original name from which its epithet is derived. Depending
upon whether you recognize two genera or just one (which more accurately
reflects relationships, according to the latest studies), the use of either
name could be correct. Neither name becomes invalid or illegitimate. Occasionally
the specific epithet cannot be transferred in that way because another species
in the second genus has already been given that epithet. In this case, the
epithet of a more recent synonym is used, or if necessary a new epithet is
published for the species.
