Many plants have been given common names. These tend to be
locally derived, so multiple names may exist for a single plant
species if it grows naturally in different parts of the world. There
are also instances where the same common name is used for different
plants. Thyme is the common name used for more than
350 species in the genus Thymus
. Only a few of these species are used for culinary purposes, so it is important to purchase the
correct plant if you want to eat it.
|Figure 2.3 Carolus Linnaeus was
a Swedish botanist and taxonomist,
referred to as the father of modern
taxonomy. In 1749, Linnaeus laid the
foundation for the classification of living
organisms when he introduced
Horticulturists use a system of binomial nomenclature and
cultivar names to identify a specific plant and thus avoid the confusion
that can be caused by common names. Binomial nomenclature
is a system that assigns a unique two-word name to each species, made up of a generic name (the genus) plus a specific
name that defines the species. It was developed by Carolus Linnaeus
in the eighteenth century (Figure 2.3). Linnaeus built upon
the work of many prior botanists. The earliest records made by
the fathers of botany date from the fifth century b.c. to the third
century a.d. and recount knowledge from Mesopotamia, Egypt,
Greece, and Rome. Arab and Asiatic botanical records from the
eighth to the twelfth century a.d. and the work of botanists from
the 1500s to the 1700s were also described by Linnaeus.
Binomial nomenclature was created in Latin, as this was a language
common to botanists from different countries. The genus
name is a Latin noun that may be the name of a person who discovered
the plant or it may somehow describe a common trait of
all the plants in the genus. The species name is a Latin adjective that
modifies the noun based on a particular characteristic of the species,
such as the color of the flowers or size of the plant. The genus
is always capitalized; the species name is in lowercase and the full
name is either italicized or underlined. (For example, the binomial
name for corn is Zea mays.
) The genus can be abbreviated by the
first letter followed by a period in instances where it has been previously
referred to in a manuscript. Sometimes the specific epithet
is designated as sp.
(plural) in cases where it is either not
known or if the writer wants to refer to all plants in the genus.
The binomial nomenclature, or Latin name, may be modified
to reflect a botanical variety or a horticultural cultivar that
is noticeably different from other plants of the same species
(though all members of a species—including the unique varieties
and cultivars—can interbreed). The modification accounts
for differences that occur in plants because of growth in various
types of soil or spontaneous mutations that may produce a different
color flower or variegated
leaves, among other traits.
Varieties are plant specimens identified in their natural environment,
whereas cultivars are those that were cultivated and
bred by man. However, many subspecies of vegetables are called varieties and the two terms are often used interchangeably. The
cultivar or variety name is set in single quotes, is not italicized,
and is limited to three words. The cultivar name either follows
the binominal or is used in place of the species name. Collections
of cultivars may be combined into larger horticultural groups.
Examples of Latin names, followed in parentheses by the
common name(s), for the culinary species of thyme include Thymus
(common thyme, garden thyme), T. herba-barona
(caraway thyme, herb baron) and Thymus × citriodorus
thyme). The ×
in T. × citriodous
is used to designate it as
a hybrid. Hybrids are a result of cross-breeding as described in
the next topic. T. serpyllum ‘Coccineus’ (red creeping thyme)
is not an edible plant but is appropriate for use in a garden path
or rock garden because of its creeping habit and colorful flowers.
The word ‘Coccineus’ set in single quotation marks indicates that
it is a cultivar name.
Plants need to be described before they can be identified. Plant
anatomical and morphological characteristics are used to generate
descriptions of plants and to group them according to their
similarities in order to identify and name them. The best times to
describe plants are when they are in full flower. Alternately, fruiting
structures will yield a great deal of information. The order of
the description follows the growth of the plant. It begins with the
roots, moves to the stem and leaves, and ends with a description
of the reproductive structures (flowers and fruits).
|Figure 2.4 Botanists are photographed in Guyana
as they identify and catalog plant specimens for
an herbarium. An herbarium is a collection of
preserved plant specimens.
Once these features have been noted, one can consult a botanical
text with a dichotomous key, field guides, illustrated encyclopedias,
seed and plant catalogs, garden centers, botanical
gardens, and herbariums for descriptions of similar plants that
have been previously identified and named. A dichotomous key
consists of paired statements that describe the characteristics of
a plant. One of the statements will apply to the plant and directs
the user to another set of paired statements. This continues until
the plant is named. Pictures, illustrations, or dried specimens can
be very helpful in the identification of plants.
Dried specimens are made by pressing the whole plant
between sheets of paper, then mounting with glue. Herbariums
are collections of pressed, dried plants that have been identified
by botanists and can be found in botanical gardens, at universities,
and in private collections (Figure 2.4). Dried specimens can be brought to an herbarium for identification by comparison to
other plants in the collection.