C H A P T E R
Plant Names and Classification
Overview
Learning Outcomes
Development of the Binomial System
of Nomenclature
Linnaeus
International Codes of Botanical
Nomenclature
Development of the Kingdom Concept
Classification of Major Groups
Species Concepts
Morphological Species Concepts
Interbreeding Species Concepts
Ecological Species Concepts
Phylogenetic Species Concepts
Eclectic Species Concepts
A Key to Major Groups of Organisms
(Exclusive of Kingdom Animalia)
Nominalistic Species Concepts
The Future of Plant Classification
SUMMARY
REVIEW QUESTIONS
DISCUSSION QUESTIONS
ADDITIONAL READING
LEARNING ONLINE
Like many wild plants, Castilleja indivisa is known
by more than one common name. It is called Texas
paintbrush or entireleaf Indian paintbrush, and it
is an annual flower native to Texas. One goal of
plant taxonomists is to assign only one Latin name
to each species. © Glenn Robertson/Getty Images
, OVERVIEW
This chapter begins with a discussion of the problems involved with the use of common names for plants, as illustrated by a survey of such
names for two related species of American spring-flowering perennials. It continues with a brief historical account of the events that led to
the development and acceptance of Linnaeus’s Binomial System of Nomenclature. The history of the development of a six-kingdom classi-
fication is presented, along with a list of the phyla and classes included in the kingdoms covered in this text. A dichotomous key to the king-
doms and phyla of organisms is provided. New information about use of DNA sequence data for plant classification is also presented. The
chapter concludes with a brief discussion of species concepts.
Learning Outcomes
1. Discuss several problems associated with the application of 4. Describe the basis for the six-kingdom classification system.
common names to organisms. 5. Distinguish among the six species grouping concepts.
2. Describe the Binomial System of Nomenclature, and discuss 6. Demonstrate the use of a dichotomous key to identify a plant.
how it developed and how it is currently used.
3. Explain the reasons for recognizing more than two kingdoms
of living organisms.
B
iologists are sometimes thought by the general public that some of the common names of Dicentra cucullaria
to be pompous when they refer to peanuts as Arachis (e.g., colicweed, Indian boys-and-girls, little blue stagger)
hypogaea or an African hoopoe bird as Upupa epops. have also been applied to Dicentra canadensis, in addi-
They aren’t, however, merely showing off or being difficult. tion to the names squirrel corn, turkey corn, turkey pea,
Rather, they’re identifying organisms by their scientific wild hyacinth, fumitory, staggerweed, and trembling stag-
names through a system that has evolved over centuries. It ger. However, the problem of the diversity and the overlap-
has become vital to us to be able to consistently distinguish ping of common names for these two plants doesn’t stop
among existing organisms (with current global estimates there. The name monkshood, for example, is widely used
of 8.7 million species), as well as those that have become for Aconitum species, which are in the Buttercup Family
extinct. (Ranunculaceae)—a family only distantly related to the
At present, all living organisms are given a single, two- Fumitory Family (Fumariaceae) of Dicentra. The names
word Latin scientific name, and many have common names. soldier’s cap, rice roots, meadow bells, and turkey corn have
Only one correct scientific name applies to all individuals of also been applied to completely unrelated plants. Both spe-
a species, no matter where they’re found, but many common cies of Dicentra are shown in Figure 15.9.
names may be given to the same species, and one common In Europe, with its many languages, common names
name may be applied to a number of different species. can become very numerous indeed. The widespread weed
The scientific name Dicentra cucullaria, for example, with the scientific name Plantago major, for example, is
was given to a spring-flowering plant native to eastern often called broad-leaved plantain in English, but it also
North America and the Columbia River basin in the West. has no fewer than 45 other English names, 11 French names,
Its unique flower shape, which looks like the baggy pants 75 Dutch names, 106 German names, and possibly as many
of a traditional Dutch costume, has resulted in its being as several hundred more names in other languages, with lit-
given the common name Dutchman’s breeches. It also, erally dozens of these common names also applying to quite
however, has the common names of little-boys’ breeches, different plants (Fig. 16.1). If it were not for the early recog-
kitten’s breeches, breeches-flower, boys-and-girls, Indian nition by biologists and others of the urgent need for world-
boys-and-girls, monkshood, white eardrops, soldier’s cap, wide uniformity in naming and classifying all organisms,
colicweed, little blue stagger, white hearts, butterfly ban- utter chaos eventually might have prevailed in communica-
ners, rice roots, and meadow bells. In addition to these tions concerning them.
English common names, the plant has Native American
names, and in the Canadian province of Quebec, it has
French names.
Often growing with Dicentra cucullaria is a related Development of the Binomial
plant, with similar leaves but with slightly differently shaped
flowers, having the scientific name Dicentra canaden-
System of Nomenclature
sis. Because of the similarities between the two plants and The first person known to attempt to organize and clas-
their close association in the woods where they occur, some sify plants was Theophrastus, the brilliant student of Plato
people in the past assumed that they were merely two dif- and Aristotle. His 4th-century B.C. classification of nearly
ferent forms of the same plant. This is reflected in the fact 500 plants into trees, shrubs, and herbs, along with his
283
, 284 Chapter 16
Figure 16.2 Carolus Linnaeus. © Photo Researchers, Inc.
Figure 16.1 Plantain (Plantago major). This plant has at least
300 different common names. Source: H. Zell/wiki/CC BY 3.0
distinctions between plants on the basis of leaf characteristics, Linnaeus
was used for hundreds of years. It was not until the 13th century
A.D. that a distinction was made between monocots and dicots
At this point, the Swedish naturalist Carolus Linnaeus
on the basis of stem structure. (1707–1778) (Fig. 16.2) began improving the way organ-
Herbalists added many plants to Theophrastus’s list, isms were named and classified. The system he established
and by the beginning of the 18th century, details of fruit and worked so well that it has persisted to the present. In fact,
flower structure, in addition to form and habit, were used in Linnaeus’s system is now used throughout the world.
classification schemes. European scholarly institutions were Linnaeus, who was nicknamed the “Little Botanist” at
beginning to bulge with thousands of plants that explorers school, inherited his passion for plants from his father, who
had brought back from around the world, and confusion over was a minister and an amateur gardener. He is said to have
scientific and common names was multiplying. been impressed at the age of 4 by his father’s remarks about
The use of Latin in schools and universities had become the uses of neighborhood plants in his home community of
widespread, and it was then customary to use descriptive Råshult, located in southern Sweden. After a brief tenure
Latin phrase names for both plants and animals. All organ- as a student at the University of Lund, he spent most of his
isms were grouped into genera (singular: genus), with the time making excursions to Lapland, Holland, France, and
first word of the Latin phrase indicating the particular genus Germany. Eventually, he became the professor of botany
to which the organisms belonged. For example, all known and medicine at Uppsala, where he inspired large numbers
mints were given phrase names (polynomials) beginning of students, 23 of whom became professors themselves. He
with the word Mentha, the name of the genus. Likewise, frequently led large field trips into the countryside, accom-
the phrases for lupines began with Lupinus, and those for panied by a musical band.
poplars began with Populus. A complete phrase name for When Linnaeus began his work, he set out to classify
spearmint read Mentha floribus spicatis, foliis oblongis ser- all known plants and animals according to their genera. In
ratis. Roughly translated, it means “Mentha with flowers in 1753, he published a two-volume work entitled Species
a spike (an elongated but compact flower cluster); leaves Plantarum, which is important as the first book used by
oblong, saw-toothed.” plant taxonomists to assign names. In this book, Linnaeus
