Fascination of Plants Day trail at the
Botanic Garden
Follow this trail and look closely – whether it’s through the magnifying glass at the trail
marker, up into the tree or down at ground level. You’ll discover a whole new world of
fascinating things about plants!
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International Fascination of Plants
Oxford University Botanic Garden & Harcourt Arboretum
18th May 2012
Trail stop 1
Magnolia grandiflora - by the Danby Arch
Look underneath the glossy evergreen leaves of this large plant. They are not green but an
orange/brown. Look closely through the magnifying glass and you will see that this colour is
due to lots of tiny hairs called indumentum. These hairs form a protective coating against
water loss and may also contain chemicals that protect against predators.
Trail stop 2
Stachys byzantina - Lamiaceae bed
Many plants in the mint family have special hairs on the leaves and/or stems. You
don’t need to look too closely at the lamb’s ears plant (Stachys byzantina) to see the hairs on
the leaves but a close look (with the magnifying glass) at the stems of the rosemary plant
(Rosmarinus officinalis) will reveal a special kind of hair. Many mint family plants contain large
amounts of special aromatic oils made from terpenes and these are stored in the modified
hairs called trichomes.
Trail stop 3
Nonea lutea - Boraginaceae bed
Plants in this botanical family nearly always are covered in conspicuous stiff hairs. These are
unicellular and mounted on a swollen base embedded in the epidermis – the surface of the
leaf. Some of the plants in this family may also have cystoliths on the surface of the leaves.
These are outgrowths of the cell wall impregnated with silica and/or calcium carbonate (chalk)
and help to provide a rough surface to the leaf, making them unpalatable to predators. Feel
the leaves and have a closer look with the magnifying glass
Trail stop 4
Davidia involucrata – the handkerchief tree
Look up high into this tree and see if you can spot the pale green/white “handkerchiefs”
hanging amongst the branches. These structures are bracts, which surround each little ball of
flowers (inflorescence). They are thought to protect the pollen on the flower from the rain –
and a good job too this summer!
International Fascination of Plants
Oxford University Botanic Garden & Harcourt Arboretum
18th May 2012
Trail stop 5
The Merton borders – Lower Garden
Get down as low as you can and take a close look at ground level. Can you see the seedlings
emerging from the sand? This large area will soon be a thriving plant community and has
been established by sowing seed from over 80 different species of plant. How many different
types of seedlings can you spot? This technique is being used to minimise the impact on the
environment of establishing a new herbaceous border – minimal water input, minimal air miles
to transport plants and minimal use of peat and plastic.
Trail stop 6
Euphorbia characias ssp. Wulfenii – Euphorbiaceae bed
Take hold of the hand lens on the post by this plant and take a closer look at the unusual
flower structure. Euphorbia flowers sit within a structure called the cyathium (from the greek
word for a cup or ladle). Around the rim of the cyathium is a ring of swollen appendages,
which are glands that secrete nectar in order to attract and reward pollinators. It is these
glands that vary so greatly in this euphorbia species. In this sub-species the nectar glands are
typically yellow and horned.
Trail stop 7
Microsorum punctatum - Fernery
The plants in this part of the glasshouses are ferns – non flowering plants. They reproduce via
spores and do not produce seeds. Turn over a frond (leaf) and take a look with the hand lens
at the structures on the underside. You will find precise and regular patterns of spore bearing
structures. These may be spots, stripes or even chain-like arrangements depending on the
species.
Trail stop 8
Semele androgyna – Lower corridor
On your way to the Palm House, stop for a few minutes and take a closer look at this strange
plant. Can you see the tiny white flowers? Do they appear to be growing out of a leaf? The
“leaf” you see in front of you is in fact a special modified stem called a phylloclade (meaning
leaf like branches) and the flowers are growing from nodes on this modified stem.
International Fascination of Plants
Oxford University Botanic Garden & Harcourt Arboretum
18th May 2012
Trail stop 9
Murraya paniculata – Palm House
The shrubby plant on your left as you enter the Palm House belongs to the Citrus family
(Rutaceae). One of the botanical characteristics of this family are the special structures on the
leaves. Find a new leaf (lighter green colour), tilt it towards the light, and have a close look
with the magnifying glass. Can you see the tiny clear windows or dots in the leaf structure?
These are called pellucid dots and contain the aromatic oils these plants are well known to
contain.
Trail stop 10
Pilocereus moritzianus – Arid House
This Venezuelan plant is not nearly as fast as its new Formula 1 racing star but it will reveal a
secret to you if you look up high. On the side of the plant that faces south (towards the
outside of the glasshouse) you will be able to spot some flowers but they are probably closed.
This plant blooms at night in the desert and is pollinated by bats and moths that are attracted
by the white petals and the musky odour the flower emits. Come in early in the morning on a
cloudy day to see the flower open before it closes up after its magical night-time display.
International Fascination of Plants
Oxford University Botanic Garden & Harcourt Arboretum
18th May 2012
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Fascination of Plants Day