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 image.


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 yellow-orange stamens.


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 yellow-orange anthers (male pollen producing organs) supported by very short (or non-existent) filaments 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 more mature.


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 visiting insects.


Photographic Equipment

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 4500.

A Flower Garden of Macroscopic Delights

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.

References

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, Alberta,Canada.

• 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.

 All comments to the author Brian Johnston are welcomed.