Environmental Engineering Reference
In-Depth Information
from Peru by Jesuit missionaries, and from Spain, it spread
throughout the world, and illustrated the need at that time for
a more refined method of classification of plants, because the
same plant was often referred to by a common name that also
was used to describe many other very different plants. To
further complicate things, plants were named by people in
their native language. Moreover, the names of plants were
cumbersome; for instance, catnip, known today as
Nepeta
cataria
, was at one time called
Nepeta floribu interrupte
spicatis pedunculatis.
Plant naming was clarified consider-
ably when Latin was agreed upon as the official language for
plant classification. Moreover, an additional task was to take
this vast body of knowledge, based primarily on the spoken
word, and compile it into written form for teaching and
instructional purposes.
Even with this common language, problems still plagued
early botanists and physiologists, because the Latin was
applied to describe the gross physical characteristics of
plants, such as flowers, bark, and leaf structure. Early
attempts were made by many to improve upon these classi-
fication schemes, and the works produced by John Ray
(1627?-1705), such as
Historia Plantarum
(1686, not to be
confused with the topic by Theophrastus of the same name),
led to a general plant-classification system that is often used
today. Ray divided the flowering plants, or angiosperms, that
protect their seeds in fruits or nuts into two broad groups
based on the number of proto-leaves a seed has in a small
depression called the kotyle, or cotyledon. Seeds with one
leaf were called monocotyledons and seeds with two leaves
were dicotyledons. As we will see in later chapters, this
single characteristic is useful on many levels; monocotyledons
grow in height only, whereas dicotyledons also expand
in girth. The Frenchman Antoine Laurent de Jussieu
(1748-1836) also investigated plant forms based on the
number of leaves that emerged from seeds and published
his work
Genera Plantarum
(de Jussieu 1789), which was
expanded upon in 1830 in
Botanicom Gallicum
by Augustin
de Candolle.
The need for a more rigorous method of classification
for plants (as well as animals) was ultimately met by the
Swede Carl Ingemarsson (1707-1778). His father, Nils
Ingemarsson, was a clergyman of the Lutheran Church.
Nils loved plants and, to young Carl's delight, placed many
unique ones around the church. Carl studied medicine rather
than the clergy as had been the hope of his father, but he also
studied botany—two fields that were linked by the common
use of plants for medicinal purposes. During this time, Carl
was asked to bring order to the messy personal collection of
biological specimens of the nearby estate of Doctor Kilian
Strobaeus (Hubbard 1916). Deemed beyond organization by
others, Carl found his calling for turning such chaos into
order, and began to show his talent for classification. Over
time, Carl Ingemarsson developed a classification system for
plants and animals termed binomial nomenclature which is
still used today. His ideas were first released in 1735 in the
12-page
System Naturae
(Linnaeus 1735). Carl Ingemarsson
is perhaps more widely recognized today as Carolus
Linnaeus, as it was the custom for scholars at that time to
take Latinized forms of their first names. In addition, the
Ingemarsson family changed their surname to Linnaeus, a
derivation of the root word for the linden tree, which is a
plant, ironically, that can tap groundwater.
The classification system developed by Linnaeus is bino-
mial, meaning two names, because it gave a generic (Genus)
and specific (species) name to each plant or animal being
classified. A genus refers to a group of related species. The
species is the smallest unit of classification and can maintain
its features through many generations. The concept of a
species can be attributed to John Ray, based on his
observations of many plant and animal specimens. Within
the binomial system, the concepts of genus and species are
related. For example, man is classified as
Homo sapiens
(L.),
where the parenthetic L. stands for Linnaeus, to indicate that
he was the first to describe and name the species for classifi-
cation purposes. If a species has different appearances, say,
spotted leaves versus plain leaves, this difference is denoted
as a variety, such as the tree
Populus deltoides
var. DN-34,
where a variety is a different type of species, much like a
poodle is a special variety of dog. A cultivated variety,
abbreviated as cultivar, is a variety grown for a particular
unique feature. Most cultivars are reproduced by cuttings,
rather than from seeds, and can be considered a clone of the
parent. Such classification can continue on in the opposite
direction to even larger groups of classification, such as
family, order, class, phylum, and kingdom. Only the genus
and species, however, is used when referring to specimens.
This binomial system is analogous to how individuals are
listed in phone books, where, for example, many people who
share a common last name are differentiated by unique first
or second names.
To ensure the adoption and use of his new method,
Linnaeus coupled the binomial system of differentiation
with another older classification method based on the readily
observable differences in the reproductive organs of differ-
ent plants. Previously in 1680, at a time when separate sexes
were thought to be a trait characteristic of mammals only,
Nehemiah Grew discovered that flowering plants
(angiosperms) had both male (stamen) and female (pistil)
reproductive structures. Pollen contained in the stamen was
necessary for production of a seed in the pistil, a process
called pollination. This idea also was studied in 1694 by the
German botanist Rudolf Jakob Camerarius (1665-1721).
Linnaeus furthered these notions and used a simple
microscope to assist his merging of the sexual classification
and binomial schemes. This was a step ahead of differentia-
ting plants based on larger more obvious structures, such as
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