Agriculture Reference
In-Depth Information
This enables us to find what we want quickly and know
that what we are buying has particular characteristics.
In the same way, the plant kingdom is classified into
major groups, such as vascular and non-vascular plants
described above, which are in turn subdivided into
smaller groups. For gardeners, the groupings of plants
which are most commonly encountered are
family
,
genus
and
species
.
Plant
families
were first described comprehensively
by the Swedish botanist Linnaeus in the eighteenth
century. His classification was originally based on
flower structure, although nowadays many other
factors such as plant chemistry and genetics are
used in addition to their external features. Many
of Linnaeus' original family names and groupings
still stand. Currently about 240 plant families are
recognized. Plant family names always end in -aceae
for example, Lamiaceae (the nettle family) or Poaceae
(the grass family). The family is an important grouping
in horticulture as all plants within a family have certain
characteristics in common, so predictions can often
be made about other family members. For example,
many members of the family Rosaceae (the rose
family) are susceptible to the disease fireblight, aiding
identification and enabling prediction of the spread of
this disease.
Within a family, plants are organized into groups of
similar plants called
genera
(sing. genus). A family
may contain many genera, such as the Asteraceae
(the daisy family) with 1,317 genera including
Lactuca
(lettuce),
Taraxacum
(dandelion) and
Dahlia,
or a few
such as Geraniaceae with just five including
Geranium
and
Erodium
.
A genus is made up of groups of similar plants
called
species
.
A species is a group of individual
plants which show the greatest degree of mutual
resemblance, and which, most importantly, are able
to breed among themselves but not with plants from
another species.
in 1735. Each kingdom was subdivided into a
hierarchy of classes, orders, genera and species
which replaced existing classification systems
and is still in use today. For plants, he used the
structure of flowers, in particular the male and
female parts, as the basis of his classification.
This 'sexual system' was a practical and easily
learned approach which enabled him and his
students to study a large number of species,
although the florid way in which he described it
caused an uproar at the time!
In addition, Linnaeus is credited with
establishing the binomial system of
nomenclature. Although the use of binomials for
plants was not new, Linnaeus applied them
consistently to all plant species alongside the
cumbersome many-worded 'phrase names'
which were current at the time and thus laid the
foundation for a simple and universal naming
system which has been adopted ever since. As
such, Linnaeus' work
Species Plantarum
, first
published in 1753, forms the basis for plant
nomenclature right up to the present day.
4
Carl Linnaeus - the Father of
Classification (1707-1778)
Carl Linnaeus (also known as Carolus Linnaeus
or Carl Linné) (Figure 4.4) worked as an assistant
and later as professor of botany at Uppsala
University in Sweden. He brought together all
recorded knowledge of the natural world known
at that time and classified it into three kingdoms:
minerals, plants and animals. He named some
7,700 plants and 4,400 animals in his lifetime
and used an innovative classification system
which was first set out in his
Systema Naturae
Figure 4.4
Carl Linnaeus dressed as a Laplander
from a painting by Hendrik Hollander in 1853. He
explored Lapland in 1732, collecting plants, birds and
rocks and used the 600-mile trip to apply his ideas
of classifi cation and nomenclature. He described
100 newly identii ed plant species in his topic
Flora
Lapponica
