Nomenclature
Classification, identification, nomenclature
Classification schemes are an
attempt to place plants in categories that are useful to the individual doing
the classifying. Because there is considerable diversity in the way in which
plants are used, as well as the appearance of plants, there are many different
plant classification systems. For botanists, however, the only universally
accepted scheme for plant classification is one that attempts to show genetic (phyllogenetic = evolutionary) relationships among plants.
Classification
assumes that members of any given group have more in common with one another
than with members of any other equivalent group. Instead of having to record
and remember separately the features and properties of each individual within a
group, we need only concern ourselves with those of the group as a whole,
knowing that the characters will apply to all members. E.g. any apple has more
in common with any other apple than it does with an orange, or a pear.
Classification,
loosely, is the assignment of like-objects to recognizable groups. It
facilitates reference to them and transmission of information about them.
Need for classification
The numbers of different kinds of plants are exceedingly
great. An estimated 300,000+, and if we include the fungi
(molds, mushrooms, toadstools), then about 450,000 different organisms.
The plant kingdom is large and diverse. It is an impossible task to record and
remember the character and properties of each one of these plants, individually.
Some kind of grouping and summarizing is essential for us to begin to
understand and utilize the vegetable world. Size and diversity of plant kingdom
makes classification necessary
Identification
– the recognition of sameness. This is a basic process of classification; the process of deciding whether or not two things are, in your
opinion, the same. It is not the same as naming.
In classifying plants, we use
our judgment to decide which plants should form groups of similar individuals. Each identification we make in doing this involves an act of
judgment on our part. A classification, then, is built up by a series of such
acts of comparison and judgment: we ask ourselves ‘are these two the same or
are they different?’ Each time we classify a new plant into a group which we
have already established, we carry out an act of identification – ‘yes, this is
the same as those’.
Taxonomic ranking - each ranking up the taxonomic hierarchical ladder - from species to
genus to family - shows an increasingly greater range of variation. The lower
the rank of a taxon (general term for any taxonomic
rank: species, genus, family, etc.), the fewer are its members and the more
they have in common with one another; the more detailed the classification
becomes and the more particular is the information about the plants concerned.
As one goes up the taxonomic
hierarchical ladder, the rankings become increasingly more inclusive; they draw
in more taxa because they allow for greater
variability.
Taxonomic hierarchy
Species -
plants of one kind, e.g. "cinnamonea.
Genus -
group of related species, e.g
Family -
group of related genera that share combinations of morphological shapes,
especially floral and fruit features. e.g. Rosaceae. (Family names are capitalized, and usually end in
_aceae.)
Order -
group of related families. E.g. Rosales. (Capitalized
and ends in _ales.)
Class -
group of related orders. Dicotyledoneae (as opposed to Monocotyledoneae).
Subdivision
- group of related classes. Angiospermae (as opposed to Gymnospermae).
Division -
group of related subdivisions. Spermatophyta (seed plants), as opposed to Thallophyta
(algae), Bryophyta (mosses and liverworts), Pteridophyta (ferns) and fern-allies, etc.
Kingdom - Plantae
Each ranking up the taxonomic
hierarchical ladder, from species to genus to family, shows an increasingly
greater range of variation; more inclusive.
The lower the rank of a taxon (general term for any taxonomic rank: species, genus,
family, etc.):
a.
the fewer are its
members; the more exclusive
b.
the more they have in common with one another.
c.
the more detailed the classification becomes (the tighter
the relationship).
d.
the more particular the information about the plants.
Example: We
have a plant, Senecio vulgaris (groundsel)
visible to us, in front of a screen. We have another plant hidden from us
behind the screen.
a.
If we are told
the hidden plant is also a Senecio vulgaris (the same species), we can predict that the
hidden plant will look very much like the plant in front of the screen. It will
share many of the same characters as the visible plant, and without seeing the
hidden plant, we’d be able to describe it. There might
be slight genetic difference as to the height of the plant or the robustness,
but it will be appreciably the same as the visible plant of the same species.
b.
If we are told
the hidden plant is in the same genus as Senecio vulgaris (Senecio sp.), we can still predict a great deal about the hidden plant,
but not as accurately as we could with the plant of the same species. There may
be hundreds of different Senecio species, and even
though they may all share a considerable amount of attributes, there will still
be greater variation than there was with the same species.
c.
If we are told
the hidden plant is in the same family as Senecio vulagaris, the composite family
(Asteraceae), we can predict even less. There are over a hundred different
genera (plural of genus) in the family, and each genus may have between one and
hundreds of species within its rank. Now, there are thousands of plants to
choose from and the shared characters are less and less. We can probably
predict the fruit type will be an achene, but little
else.
d.
If we are told
the hidden plant is in the same order as Senecio vulgaris (Asterales),
we can predict less still about the hidden plant. On top of the thousands of
plants that share some general characters with Senecio vulgaris, the order, Asterales,
are composed of even more families, such as Campanulaceae
and Dipsacaceae.
e.
And so on and so
forth, up the hierarchical ladder to class, subdivision, division, and kingdom,
each succeeding rung in the hierarchy becoming less predictive because there
are fewer and fewer shared characters with the individual Senecio vulgaris, the plant with which we began.
Scientific names - The part of systematic or taxonomic botany that deals with the
giving of names to plants is referred to as nomenclature. The purpose of a name is to act as an easy means of
reference, as an aid to communication.
1. Names
impart some information about a plant: flower color, leaf shape, flavor,
location, season of blooming and, especially, relationships.
2. This
is true of all names, such as your own first names and surnames, not only of
scientific names of plants.
3. The
use of a name avoids the use of a descriptive phrase every time we wish to
refer to an object, or group of objects. It is easier to say “I saw some
bluebells in the woods today” than it is to say, “I saw some plants with blue
elongated bell-shaped flowers in groups at the ends of long stalks and with
parallel-sided leaves about a foot long, all springing from ground level in the
woods today”.
4. To
some extent, however, that is how plants had previously been referred. A name,
then, stands, as it were, in place of the object itself and acts as means of
reference to it.
By the time Linnaeus came
along and wrote his famous and influential treatises, Genera Plantarum (1737) and Species Plantarum
(1753), plants were described in a polynomial system of nomenclature. Polynomials included a single word for
a plant (what we now refer to as a genus), followed by a lengthy list of
descriptive terms in Latin.
E.g. Ranunculus
calycibus retroflexis, pedunculis falcatis, caule erecto, folius
compositis. Roughly, it means, the buttercup
with reflexed sepals, curved flower stalks, erect
stem, and compound leaves.
Polynomials
were not standardized, different polynomials existed
for the same plant, and was cumbersome to remember.
One
of Linnaeus’ great accomplishments was to introduce, almost inadvertently, a
binomial system of nomenclature, or the 2-word scientific name. (The binomial
system is now used for all known organisms). He used this system of reference
consistently in Species Plantarum, a work
which describes and names 5,900 plants, all the plants known to Linnaeus.
The
binomial system simplified scientific names. In 1867, a group of botanists at
the International Botanical Congress in
Scientific plant names must be in Latin.
1. This overcomes the difficulty of multiplicity of
different languages which makes common names confusing and unsatisfactory.
2. Latin was the common language of learned men in
3. Latin is essentially a “dead” language - that is, it is
no longer spoken as a native tongue by any people, avoiding elements of
national bias and jealousy, and words are no longer being added or subtracted
to the language. (It has a stable glossary and grammar).
Of what is a scientific name composed?
Each kind of organism is
known as a species, and similar
species form a group called a genus.
Each species has a scientific name in Latin that consists of two elements: the
first is the genus and the second is the specific epithet. Together they are
referred to as a binomial (literally
- 2 names), and is always either italicized or underlined.
Binomial -
the binomial is comprised of a genus and a specific epithet.
1.
Genus - the
first word in a binomial, is always a singular noun,
written with a capitalized initial letter -
2.
Species -
made up of 2 parts: genus and specific epithet.
Binomial -
generic name (genus) + specific epithet. It provides a summary of affinities
which acts as an aid to memory, and enables one to make inferences about plants
unknown to us. E.g. groundsel or Senecio vulgaris and
The binomial grouping reflects natural relationships
based on shared vegetative and reproductive characteristics.
Our names are, essentially, binomials. In the phone book we
are listed last name first. Our last names (surnames) act as genera
: Lennon, for example. Which Lennon? John Lennon describes which Lennon
we are referring to, and distinguishes him from Robert Lennon, Sally Lennon,
and Roberta Lennon. Altho, all very similar
genetically, they each represent very particular expressions of self that are
different from one another.
Citation of authority - refers to the first person who validly published
the name, or first described the plant, or who first placed the plant in a
particular genus.. E.g. Primula vulgaris
Huds. Or, Zea
mays L. Authority names are often abbreviated and, when in
reference to Linnaeus, abbreviated with only the first letter of his last name,
L. The authority is not part of the botanical name but is often added for
purposes of precision.
A scientific name is unique
in that it refers to only one species and is universally accepted among
scientists
. Trinomial - refers to the rank below that of species - subspecies
or variety. A plant group can be so different in the wild from the general
species originally described,
that it warrants a botanical variety classification below that of
species. E.g. Buxus microphylla Sieb. and Zucc. var.
japonica Rehd.
and Wils., which is native
to Japan, and Buxus microphylla
var. koreana
Nakai, which is native to
Cultivars are cultivated varieties, a term used in both
agriculture and horticulture (a contraction of cultivated variety). If
propagated by vegetative means they are referred to as “clones”; if by seeds
they are referred to as “lines”. Cultivar is abbreviated as cv. It is often a distinct variant selected by
someone who believed it was uniquely different from any plant already in
cultivation. Could refer to a difference in flower color, spines vs. no spines,
etc. (The cultivar name is always capitalized but never underlined.)
Common names
(vernacular names, familiar names) -
common names are very often descriptive and poetic references to plants. However, a common name may refer to more than
one plant or, conversely, many plants may have the same common name. Common
names are often ambiguous and often regional or local, rarely universal.
E.g. Bird of
paradise may be Strelitzia reginae,
from the Strelitziaceae, a monocot from the tropics.
But in the North American southwest deserts, Bird of paradise refers to Caesalpinia gilessii,
a leguminous dicot from the Fabaceae.
Or the very same plant, say Arbutus unedo, may be known by
different common names, depending on geography or language: Osage orange is also known as bodek, bois d’arc, hedge osage, horse apple, mock orange, wild orange, etc.
The Jerusalem cherry is a woody plant about 1’ tall, its
fruit is a berry, not a cherry, and it doesn’t come from
In
Common names for plants do not indicate any
relationship with other plants; there is no hierarchy of classification, and
therefore no predictive value, and evolutionary relationship implied by the
name.
More curious common names
1.
pineapple –
neither a pine nor an apple
2.
peppergrass – not
a pepper, nor a member of the grass family
3.
The logic behind
names such as “ramping fumitory”, “bastard toadflax”, or “bouncing bet” is not
very apparent.
4.
Kentucky
bluegrass was introduced from
Some scientific names are worth pondering as well:
1.
Viola purpurea is yellow flowered, not purple as the specific
epithet implies.
2.
Unifolium bifolium – okay, is it
one-leaved or two?
Some names of local plants:
1.
Acacia greggii is also known as catclaw or
“wait-a-minute-bush”
2.
Peucephyllum schottii is known
as desert fir, and its dark green leaves resemble the needles of firs
3.
Petalonyx thurberi, known
as sandpaper plant, is readily
apparent when you rub the leaves of the shrub.
4.
Larrea tridentata – creosote, referring to the olfactory similarity to the pungent wood
preservative used on fence posts and telephone poles.
5.
Hymenoclea salsola, cheese-bush, smell like cheese.
6.
Malva parviflora, cheese-weed,
produces wheel-shaped fruits composed of one-seeded sections.