Above: Common Spotted Orchid
(Dactylorhiza fuchsii) may reach
about 40 cm in height. (Family:
These orchids were growing on a
calcareous sloped roadside in Kent
(Britain) along with many other
flowering plants, some of which are
Left: The Tufted Vetch (Vicia
cracca) may grow up to 2 m
supported by its branched tendrils.
(Family:Fabaceae, the Pea Family,
formerly Leguminosae). As a
member of the Pea Family it forms
mutualistic symbiosis with
nitrogen-fixing bacteria in root
nodules which supply the plant with
nitrogen in a usable form.
Here it is growing among bedstraw,
which has 4-petalled white flowers
(based on the locale and habitat
this is probably Hedge Bedstraw,
Galium mollugo, Bedstraw family,
Rubiaceae) - a close examination of
the leaves would enable the species
to be confirmed.
The Tufted Vetch was also growing among Hairy St John's-wort (Hypericum hirsutum, St John's-wort family,
Clusiaceae) below. St John's-worts can be recognised by their 5 usually yellow petals and many stamens.
This particular species has pale yellow petals, a hairy round stem and stalked black 'dots' along the edges of
This Hypericum is a rich source of hypericin, a chemical with the unwieldy systematic name of:
(!) or hexahydroxy-dimethyl-naphthodianthrone and which is manufactured by several members of the
genus. We shall call is simply 'hypericin'.
This chemical is produced in black nodular glands, chiefly in the black stalked 'dots' visible on the sepals
and bracts in these photos.
Hypericin is a pigment which undergoes a
photodynamic reaction with visible light and
oxygen. This gives it antibacterial and
antiviral properties, as it kills these microbes
in the presence of light by oxidising their
components. Hypericin also causes
hypericism in animals which consume too
much st john's-wort. this causes skin
irritation as the hypericin reacts with light
and oxygen in the skin and also causes high
body temperature and sometimes also
death. Hypericin is presumably toxic to many
insects too, although the beetle Chrysolina
brunsvicensis specialises in feeding on
Hypericum hirsutum and has taste sensors
in its tarsi (feet) which can taste hypericin.
Hypericin preferentially accumulates in
cancer tissues and has potential therapeutic
value as an anti-cancer agent: the cancer
could be loaded with hypericin and then
illuminated to kill it.
Hypericin also has potential as an
anti-retroviral agent, inactivating HIV virions,
for example (by apparently oxidisng the p24
capsid protein, in the presence of light, and
preventing uncoating). It has also been used
as an antidepressant.
This Common Spotted Orchid (left)
was visibly different from the others - it
apparently has a reduced central lobe
on its labellum (lower lip) on at least
some flowers reminiscent of the Heath
Spotted orchid (Dactylorhiza
maculata). The two species also
produce a sterile hybrid on occasion.
However, since Heath Spotted Orchid
occurs very rarely in this region of
Britain it seems unlikely that this plant
is anything other than a Common
Spotted Orchid. There is always
considerable variation within species.
The Marbled White (Melanargia galathea, subspecies serena) butterfly above, frequents calcareous
grassland. It lays its eggs amongst grasses, upon which the larvae feed the following spring.
Snails thrive on calcareous grassland since they need plenty of calcium carbonate (chalk) to build
their shells. This snail belongs to the genus Monacha and is probably either Monacha cantiana (the
Kentish snail) or the similar Monacha cartusiana.
Article created: 23/9/2016
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