Close-up View of a
by Brian Johnston (Canada)
This beautiful wildflower with
its blue-purple, bell-shaped flowers, grows along the bank of a
stream near my home.
The genus name Campanula
derives from the Latin campana
which means bell,
(referring to the flower’s shape).
The flower is a member of the
Bellflower family (Campanulaceae).
The first image in the
article, and the two below, show typical 20 to 40 cm high
plants. Flowers are from 2 to 3 cm long, and hang in a
“drooping” manner from the tips of stems. Notice that the
thin wiry stem hardly seems sturdy enough to support the blooms.
The higher up the stem you
look, the narrower are the oval dark green leaves. The one
shown below was approximately one third of the way up the stem.
The bud on the left below is
at an earlier stage of development than that on the right.
It is a paler shade of pink, and the five sepals (modified leaves) at
its base still cling to the unopened petals. Later these
sepals curl away from the petals, as shown in the right-hand
Instead of having many flowers
clumped together, the plant shown in the images below has them
strung out along the stem.
Each flower has five
petals that are bisected by a longitudinal groove at their
midpoints. A prominent pistil is surrounded by shorter
Five pointed green sepals are
located at the base of the flower. Notice also, the fine
hairs that ring each petal along its edge.
The surface material of a
petal is shiny in nature, and at the proper angle reflects
light, producing “highlights” on the surface.
As can be seen below, the
apparent colour of the petal also depends on the angle of the
light with respect to the viewer. (The petal hairs are
particularly noticeable in this image.)
Depth of field is an important
consideration in macro-photography. The image on the right
shows much greater depth of field than that on the left, due to
the use of a smaller aperture, (f 16 compared to f 5.6).
The two images that follow
show the stigma (female
pollen accepting organ) of a flower. The stigma on the
right is more mature, shown by the length of the three lobes and
the amount of “curling” of their tips. The upper surfaces
of the lobes are covered in fine white hair-like protuberances.
By removing the flower’s
petals, you can more easily see the reproductive organs.
At the tip of the pistil is the (immature) stigma. It is
supported by a very long, stocky purple style which is covered with
white scaly material. Five thread-like stamens, composed of long
(male pollen producing organs) supported by very short (or
surround the base of the pistil. Below the stamens is the
startlingly white ovary (seed producing organ).
A close-up of an immature
stigma, with its incompletely unfurled lobes, can be seen
below. The image on the right is a photomicrograph of the
style showing the many short protuberances that help hold the
multitude of pollen grains to the surface.
For comparison, here is
another stigma which has longer stigma lobes, and is therefore
A completely mature stigma is
shown in the two images below. Note in the image at right,
how the purple covering splits to expose the white hairy stigma
lobes. (The images in the article were taken over a two
year period. The two images here were obtained the second
year, when for some reason all
of the plants in the patch suffered from the same ugly
problem. Droplets of what appear to be hardened, deep
purple liquid spot the top portions of the styles. I was
unable to determine the reason.)
Under the microscope, the
details of the surface of the stigma are revealed. The
surface is covered in hair-like protuberances which increase in
length towards the middle of the lobe. The image at right
shows spherical pollen grains clinging to short protuberances
near a lobe’s edge.
The yellow-orange stamens are
irregular in shape, some fairly straight, and others quite bent
and twisted. Notice in the left-hand image, the hairy
surface of the white ovary.
Two photomicrographs of an
anther follow. Many pollen grains can be seen adhering to
the surface in the low magnification image on the left.
Although the upper portion of
the style is purple in colour, at its base, near the ovary, the
colour is often white or pale green. The images show
pollen grains clinging in clumps to the hairs on the surface.
The bellflower has an
interesting strategy to prevent self-pollination. While
the pollen of a particular flower is being released by the
stamens, the three lobes of the stigma are pressed tightly
together. Only when pollen generation is finished, do the
three lobes unfurl and expose their pollen receptive surfaces to
Two thirds of the
macro-photographs were taken with an eight megapixel Sony
CyberShot DSC-F 828 equipped with achromatic close-up lenses
(Canon 250D, Nikon 5T, 6T, Sony VCL-M3358, and shorter focal
length achromat) used singly or in combination. The lenses screw
into the 58 mm filter threads of the camera lens. (These
produce a magnification of from 0.5X to 10X for a 4x6 inch
image.) Still higher magnifications were obtained by using
a macro coupler (which has two male threads) to attach a reversed 50 mm focal length
f 1.4 Olympus SLR lens to the F 828. (The magnification
here is about 14X for a 4x6 inch image.) The remainder of the
photographs were taken with an eight megapixel Canon 20D DSLR
equipped with a Canon EF 100 mm f 2.8 Macro lens which focuses
to 1:1. The photomicrographs were taken with a Leitz SM-Pol
microscope (using a dark ground condenser), and the Coolpix
A Flower Garden of
A complete graphical index of
all of my flower articles can be found here.
The Colourful World
of Chemical Crystals
A complete graphical index of
all of my crystal articles can be found here.
The following references have
been found to be valuable in the identification of wildflowers,
and they are also a good source of information about them.
- Dickinson, Timothy, et
al. 2004. The ROM Field Guide to Wildflowers of
Ontario. Royal Ontario Museum & McClelland and
Stewart Ltd, Toronto, Canada.
- Thieret, John W. et al.
National Audubon Society Field Guide to North American
Wildflowers - Eastern Region. 2002. Alfred A. Knopf,
Inc. (Chanticleer Press, Inc. New York)
- Kershaw, Linda. 2002.
Ontario Wildflowers. Lone Pine Publishing, Edmonton,
- Royer, France and
Dickinson, Richard. 1999. Weeds of Canada.
University of Alberta Press and Lone Pine Publishing,
Edmonton, Alberta, Canada.
- Crockett, Lawrence, J.
2003. A Field Guide to Weeds (Based on Wildly
Successful Plants, 1977) Sterling Publishing Company,
Inc. New York, NY.
- Mathews, Schuyler
F. 2003. A Field Guide to Wildflowers
(Adapted from Field Book of American Wildflowers, 1902),
Sterling Publishing Company, Inc. New York, NY.
- Barker, Joan.
2004. The Encyclopedia of North American
Wildflowers. Parragon Publishing, Bath, UK.
Microscopy UK or their contributors.
Published in the
May 2014 edition of Micscape.
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