Plants for Man—Their Diversity, Codification and Exploitation
| Author | J.P.M. Brenan |
| Published date | 01 April 1981 |
| Date | 01 April 1981 |
| DOI | http://doi.org/10.1177/004711788100700103 |
| Subject Matter | Articles |
1005
PLANTS
FOR
MAN—THEIR
DIVERSITY,
CODIFICATION
AND
EXPLOITATION
J.
P.
M.
BRENAN
Too
often
we
forget
the
ultimate
dependence
of
us
all
on
plants.
For
the
city-dweller
it
is
too
easy,
with
frozen
or
tinned
vegetables
in
the
supermarket,
fresh
vegetables
on
the
greengrocer’s
shelf,
and
living
plants
mainly
seen
in
small
back-gardens,
parks
or
window-boxes.
The
meat
we
eat
or
the
fish
we
fry-all
is
ultimately
and
totally
dependent
on
green
plants
on
land
or
in
the
water.
For
agricultural
peoples
the
message
is
easier
to
discern,
but
nevertheless
the
same-without
plants,
man’s
survival
would
be
impossible.
The
green
plant
is
able
to
manufacture
organic
matter,
suit-
able
for
nourishing
men
and
animals,
from
simple
components-
sunlight,
water,
oxygen
from
the
air,
inorganic
salts
from
the
soil.
It
is
this
property
that
confers
on
plants
their
unique
significance
for
other
living
beings
and
has
made
them
so
successful
in
cover-
ing
the
land-surface
of
the
world.
Except
under
conditions
of
extreme
cold
or
aridity,
there
will
be
plants
found
and
generally
in
variety
and
profusion.
The
diversity
of
plants
is
great.
In
Britain
with
a
relatively
poor
and
limited
flora,
reflecting
the
destruction
caused
by
past
glaciations,
there
are
nevertheless
some
1500
&dquo;orthodox&dquo;
native
species
of
higher
plants
(flowering
plants
and
ferns).
In
the
world
as
a
whole,
although
no
accurate
figures
are
available
or
possible,
the
likely
ultimate
total
is
in
the
region
of
500,000
species,
rang-
ing
in
form
and
size
from
minute
duckweeds
to
great
forest
trees.
If
we
are
to
know
and
use
plants
for
whatever
purpose,
it
is
essential
that
there
should
be
some
classification
or
ordered
system
applied
to
this
multitude,
if
only
to
find
our
way
through
it
or
to
locate
a
particular
sort
of
plant.
Many
different
systems
have been
used,
based
on
various
properties
or
features
of
plants,
and
often
designed
to
serve
a
particular
purpose
or
need.
Some
of
the
earliest
attempts,
by
the
ancient
Greeks,
made
a
primary
division
on
habit-trees,
shrubs,
undershrubs
and
herbs.
Whether
plants
were
cultivated
or
wild
was
another
criterion.
Categories
were
also
established
based
on
the
uses
of
plants
for
food
and
medicine.
Such
systems
have
been
called
&dquo;artificial&dquo;,
but
may
at
times
be
still
useful
and
practical
1006
in
relation
to
a
particular
need.
For
example,
to
classify
plants
on
the
basis
of
whether
they
are
hardy
or
tender,
or
whether
they
are
annual
or
perennial
herbs,
shrubs,
trees,
or
herbaceous
or
woody
climbers
may
be
a
highly
practical
one
for
the
horticulturist.
However
these
are
not
the
most
generally
useful
systems.
Those
who
have
studied
most
deeply
the
science
or
art
of
classify-
ing
plants
and
animals-the
practice
of
taxonomy-these
taxono-
mists
would
usually
agree
that
the
most
useful
system
is
one
based
on
natural
relationships
and
reflecting
as
far
as
possible
affinities .
based ~ on
community
of
ancestry:
in
other
words
a
system
based
on
evolution.
Time
is
a
dimension
here,
and
our
knowledge
of
how
evolution
has
developed
in
the
past
is
more
often
than
not
sadly
deficient
or
even
totally
lacking.
Community
of
ancestry
is
thus
often
inferred
rather
than
proven.
However,
the
situation
is
not
as
precarious
as
might
be
thought
and
there
is
an
abundance
of
groups
of
different
plants
whose
common
ancestry
and
close
relationship
are
generally
agreed:
i
the
clovers
in
our
fields,
the
pines
in
our
woods
and
gardens,
grasses
everywhere-though
all
comprising
many
clearly
different
&dquo;sorts&dquo;,
there
is
no
argument
that
each
of
these
groups
is
natural
and
that
its
components
are
genuinely
related
by
ancestry.
They
are
considered
natural
be-
cause
each
group,
though
internally
diverse,
exhibits
various
cor-
related
properties
or
features.
Pines,
for
example,
are
woody,
usually
trees,
evergreen,
with
needle-like
leaves
in
clusters;
they
bear
cones
woody
in
texture
when
ripe
and
containing
usually
winged
seeds;
they
have
a
characteristic
timber,
and
produce
strongly
scented
resins;
and
so
on.
One
can
thus
predict
that
any
pine
will
have
any one
of
a
number
of
different
properties,
and
this
ability
to
predict
can
be
of
immense
and
varied
practical
use.
Modern
plant
taxonomy
has
developed
as
part
of
its
system
a
hierarchy
of
grades
(sometimes
called
&dquo;taxa&dquo;).
The
most
com-
monly
used
are,
in
descending
order
of
importance,
the
family,
the
genus,
the
species
and
its
varieties.
Daisies,
dandelions,
chrysan-
themums,
thistles,
etc.,
with
their
characteristic
flower-heads
as
well
as
various
other
common
features,
are
put
into
the
family
Compositae;
all
grasses
are
placed
together
in
the
family
Gram-
ineae ;
the
numerous
oaks
comprise
the
genus
Quercus;
clovers
form
the
genus
Trifolium.
White
Clover
is
the
species
Trifolium
rcpens
with
various
subordinate
races
and
varieties,
cultivated
and
wild.
Obviously
this
is
a
very
simplified
picture
of
a
much
more
complex
system.
The
hierarchy
of
taxa
is
a
device of
the
human
mind
for
expressing
by
a
convenient
system
of
pigeon-holes
a
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