View of the Hybrid
Passiflora x belotii
(P. alata x P. caerulea)
by Brian Johnston (Canada)
When you take a
flower in your hand and really look at it,
In an earlier Micscape article, I
investigated two members of the Passifloraceae
family – Passiflora caerulea,
and Passiflora coccinea x incarnata.
this article, I will describe the extremely beautiful hybrid Passiflora x belotti, which was
produced by crossing P. alata
with P. caerulea.
Unlike the other two species, this one has an absolutely wonderful
In 1824, Dr. Lindley named this
hybrid Passiflora alato-caerulea,
over the years it has been given other names: Passiflora munroi, Passiflora pfortii, Passiflora x belotii, etc.
Today, one of the commonest names is Passion Flower ‘Imperatrice Eugenie’. The
dedication is to the wife of Emperor Napoleon III.
All Passion Flower blooms are
strikingly complex, and seem almost alien when compared with simpler
flowers. Sepals, petals, coronal filaments, and reproductive
structures all combine to form an amazing botanical spectacle.
it's your world
for the moment. I want to give that world to
Most people in the city rush around so,
they have no
time to look at a flower. I want them to see
it whether they
want to or not.
- Georgia O'Keeffe (Artist)
As usual, my purpose is to show
that the beauty of a flower, when viewed from a distance, is only part
of the picture. When viewed close up – very close up, the structures that
combine to form the flower have a beauty all of their own! (Note:
As the camera moves closer to a large flower, it becomes more and more
difficult to keep everything in the picture in focus.
Photographers refer to this as a ‘depth of field’ problem, and it
requires a particular part of the flower to be chosen to be ‘in
focus’. In the image on the left below, I have chosen the purple
coronal filaments to be in focus, while in the image on the right, I
have chosen the more distant reproductive structures to appear in
focus.) If you look at the image on the right, you will notice
that the flower’s reproductive structures (stigmas, ovary, and anthers)
are held by a sturdy green, rod-like structure which is called the androgynophore.
As the camera moves closer to a
flower, this depth of field problem becomes more severe.
A mature Passion Flower bloom can
be seen below. What however, did the bud stage look like?
The answer can be seen in the image
that follows. Keep in mind that the Passion Flower plant is a
vine that holds itself aloft by having its tendrils curl around nearby
plants, or other inanimate structures. One such tendril can be
seen in the image. Notice in particular, the strange, tiny
bulbous structure growing from the leaf stalk, just to the right of
centre in the image. This is a nectariferous
Much closer views of a
nectariferous gland can be seen below. These glands produce a
sweet, viscous liquid called nectar that attracts insects. In
some species, the nectar attracts insects to help fertilize the flower,
and other species, it attracts insects that devour a particular
predator that might eat the plant’s tissues, or suck the juices from
Three additional images that show
these glands can be seen below. If no insect partakes of the
liquid refreshment supplied by the glands, the droplets become so large
that surface tension can no longer hold them in position, and they fall
onto whatever is immediately beneath.
Let’s return to the bud-stage of
the blooming process. The bud is protected by three modified
leaflets. Within this protective envelope, there are five sepals
(modified leaves) which in turn protect the flower’s petals. Each
sepal is tipped by a slender spike.
These modified leaflets and sepals
can be seen more clearly in another bud.
Notice the interesting structural
engineering involved at the point of connection of a bud stalk to the
main vine. The two stalks which angle directly left are connected
Tendrils that have not come into
contact with something to hold on to, seem to form neat, regular coils.
However, when a tendril does find a
‘foot-hold’, it certainly seems to make certain that it won’t be
Over a period of many days, each
bud grows in overall size, with its length increasing faster than its
diameter. Notice that the length of the sepal spikes has not kept
up with the overall growth.
Eventually, the sepals begin
to separate as the time of blooming approaches. This reveals the
pale pink colouration of the flower’s petals beneath.
This stage can be seen more clearly
in the images that follow. Both the sepals and petals of the
Passion Flower are thick and fleshy. If you look carefully, you
can see that the sepals have begun to lose their green colouration
along the edges. Interestingly, the inner surface of each sepal is
In order to see what was inside a
bud before it bloomed, I cut away the outer structures. The
result can be seen below. Notice how neatly packed are all of the
flower’s component parts! A ring of purple coronal filaments encloses the just
visible yellow anthers, and almost white stigma pads.
The higher magnification
macro-photographs that follow show the blotchy purple and white
colouration of the coronal filaments.
A different angle reveals the
packed reproductive structures within the bud.
The tips of some of the coronal
filaments begin to curve as soon as the restriction caused by the outer
envelope of petals is removed.
Within the bud, the stigma pad and
green supporting style have fully formed, ready to open out to their
final position in the flower.
Two views of the receptive surface
of a stigma pad reveal that the surface is covered with microscopic
projections. These increase its surface area, and thus increase the
probability of pollen capture when the flower blooms, and insects visit.
Once a bud opens – a process that
takes a couple of hours – the flower is revealed in all its complex
glory. In the image that follows, the five outer, paler ‘petals’
are actually the sepals mentioned earlier. The five pinkish-red
structures are the real petals.
Viewed from the back, the three
leaflets that protected the bud are visible, as are the five
green-backed sepals. Five pink petals can be seen in the gaps
between the sepals.
If the three leaflets are removed,
the bulbous base of the flower becomes visible. In many flowers
this might be the ovary, but not in this case – as we will see
later. (Notice the interesting pie-shaped segments in the base.)
If in addition to the leaflets, the
sepals and petals are removed from the flower, the multiple rings of
coronal filaments become visible. The flower stalk is not strong
enough to support the weight of the flower, and so it usually rests on
a lower part of the plant, or simply hangs down.
It’s finally time to take a closer
look at the flower’s reproductive structures. Closest to you are
the three stigmas, held at approximately 120 degree angles by their
styles. (Notice that the receptive surfaces of the stigmas are
facing away from you.) Next comes the pale green, almost
spherical ovary. Beneath the ovary are the five yellow anthers
(again facing away from you), each supported by its sturdy,
The closer view shown below reveals
these structures more clearly.
Each stigma pad (facing down, and
pale yellow in colour) is connected to its green, supporting filament
in a particularly sculptural way.
Similarly, each downward facing
anther is connected to its supporting filament. Here however, the
connection between them is a thread-like ribbon of tissue which permits
the anther to wobble about if the flower is moved, or if there is air
movement around the plant.
The lower surface of the anther is
liberally coated with pollen. Notice the raised sections of the
anther’s surface at the edges, and down the middle.
In order to obtain the
images, I carefully cut transversely through the flower’s ovary to
remove the top-most section of the androgynophore containing the styles
This allows the filaments and
anthers to be more easily seen.
Next, I cut transversely through
the base of the androgynophore to remove the male reproductive
organs. This allows the multiple layers of coronal filaments to
be completely visible. The long
filaments form the flower’s outer
corona. If you look closely at the right-hand image, you
will see that near the centre of the flower, there are several rings of
much shorter filaments.
These form the inner corona of
belotii plants sometimes have slight variations in
colour. One of these variations is the number of white bands that
occur on the coronal filaments.
Some botanists believe that the
concentric coloured rings, or bands, visible in the flower are a
mechanism to guide insects towards the centre of the bloom where the
nectar is to be found. Of course, on the way to this sugary
treat, the insects may come in contact with anthers and stigma, and
therefore promote fertilization.
Where exactly is this nectar to be
found? It is held in a shallow, donut-shaped reservoir around the
(stub of the) androgynophore. The circular outer wall of this
reservoir is within the wide purple band that can be seen in the images
The shallow reservoir containing
the flower’s nectar is the light (almost white) ring around the
androgynophore stub. The purple ridge holding the nectar in place
is called the limen. The
ring of very short coronal filaments just beyond the ridge is called
The two images that follow show the
tops (left image), and bases (right image) of the inner corona
In the image below, the ring
between the limen and operculum can be seen to have a rough,
The two images that follow show the
wall-like limen that contains nectar. In both images, it is just
possible to see the shiny surface of the sticky liquid.
Finally, a brief look at this
plant’s leaves. All are three-lobed, with mature leaves being
dark green, and young ones a lighter shade of green.
Images of the upper (left), and
lower (right) surfaces of a leaf reveal the irregular vein pattern on
flowers look almost good enough to eat. This would however, be a very bad idea, since the plant
contains poisonous alkaloids (e.g. passiflorine), and cyanogenic
glucosides (e.g. hydrocyanic acid). Tissues of the plant may also
contain calcium oxalate crystals, which are also poisonous.
As a macro-photographer, I
particularly enjoy capturing unusual, complex flowers and their
hybrids are just about as good as it gets!
The low magnification, (to 1:1),
macro-photographs were taken using a 13 megapixel Canon 5D full frame
DSLR, using a Canon EF 180 mm 1:3.5 L Macro lens.
An 8 megapixel Canon 20D DSLR,
equipped with a specialized high magnification (1x to 5x) Canon macro
lens, the MP-E 65 mm 1:2.8, was used to take the remainder of the
Zomlefer, Wendy R. 1994. Guide to
Flowering Plant Families. The University of North Carolina Press,
Chapel Hill & London.
A Flower Garden of
A complete graphical index of all
of my flower articles can be found here.
The Colourful World of
A complete graphical index of all
of my crystal articles can be found here.
Microscopy UK or their contributors.
Published in the
December 2009 edition of Micscape.
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