Close-up View of the Wildflower
by Brian Johnston (Canada)
An infinite Alas-
The tube uplifts
a signal Bud
And then a
of the Suns
This was the first article that I wrote for Micscape. At the
time, I was not happy with the quality of the photographs that I had
taken, so I put it in the "maybe someday" file. Now, seven
years later, I have decided to let it appear on Micscape, warts and all!
The dandelion is one of the most recognized perennial weeds in Europe
and North America. In early spring and fall, the ubiquitous
carpets of yellow flowers are either considered a curse, or a thing of
beauty, depending on whether they are in your lawn or in a field beside
the road. It is thought that the English name is a corruption of
the French "Dent de Lion", and Latin "Dens leonis", meaning teeth of
the lion. This may be due to the roughly toothed appearance of
The scientific name for the dandelion is Taraxacum officinale
and it is
a member of the Compositae
family. Strangely, the bloom is not a
single flower! It is actually a composite of many individual
flowers, called florets. ( Each petal then, is a single flower!
) These florets are held above the ground by a tubular upright
stem that can be up to 45 cm in length. The bloom, florets and
stem can be seen in the images below.
At the base of each flower-head is a ring of narrow green bracts
called the involucre. Some of these stand upright to support the
immature florets before the flower opens up (left image), and some hang
down to form a barricade against small insects that might crawl up the
stem and injure the bloom (right image).
Each of the florets mentioned earlier is notched at the edge into five
teeth, each tooth representing a petal, and lower down towards the
stem, is narrowed into a tube which rests on an ovary containing a
single ovule. In the tiny tube is the nectar so sought after by
bees and many other flying insects. The stigma grows up through
the tube formed by the anthers and is covered with pollen. As can
be seen in the two images below, the stigma is split at the end into
two curling lobes.
This photograph shows a bloom at an early stage, in which the florets
have not fully opened by moving away from the central axis of the
plant. Tiny immature light green seeds can be seen at the bases
of the florets. The fine white fibers that will eventually form
the white ball (at a later stage) are visible between the yellow
If a single floret is carefully removed from the bloom, it is possible
to see clearly all of the parts of a single dandelion flower. At
the base is the growing seed. Above this is the stalk surrounded
by the tuft of white fiber that will become part of the white ball that
carries the mature seed to its destination. Higher is the yellow
floret. Crowning the flower is the pollen covered stigma.
When viewed under the microscope, the structure of the stigma can be
seen more clearly. On the left is an image of the stigma
before it branches into two lobes. Notice the sharp spikes
and the pollen which clings to the surface. The photomicrograph
on the right shows the two lobes. Handling has dislodged much of
the pollen that originally covered the surfaces.
The bi-lobed nature of the stigma is more evident in the image
below. The pollen remains in the protected areas within the loops
of the two lobes.
A higher magnification shows clearly the very large number of pollen
that cling to the inner surface of each lobe.
By adjusting the focus of the dark-ground condenser on the microscope,
it is possible to increase the contrast in the final image. The
spikes on the surface in the more highly magnified right image seem to
help in the attachment of the pollen.
As can be seen below, most of the surface area of the bloom is covered
by these pollen covered stigmas. Insects drinking the nectar,
smear themselves with pollen grains and carry them to other flowers,
When the entire head of the bloom has matured, all of the florets close
up within the green bracts that lie beneath, and the bloom returns
almost to the appearance it had as a bud. The withered yellow
florets are blown away by the wind, leaving the seeds connected by a
stalk to tufts of hair. In the images below, some of the bracts
have been removed to show the structure beneath. Notice the milky
juice that exudes from the broken bracts. This juice causes
difficult to remove brown spots, when it comes in contact with human
As time passes, this structure opens up into a gossamer ball, the
whiteness of which is striking.
This ball is made up of myriads of plumed seeds or pappus, ready to be
blown off when completely ripe, by the slightest breeze.
A closer view reveals that each seed is covered by tiny spikes.
These projections may help the seed to attach to the soil when it
finally touches down from its aerial journey.
When all the seeds have been blown off by the wind, the disk to which
the were attached remains bare, surrounded by the sheathing
bracts. In the middle ages the dandelion received the name
'Priest's Crown', when a priest's shorn head was a familiar object.
Although considered a botanical pest, the common dandelion is an
amazingly complex and beautiful object.
The low magnification photographs
in the article were taken using a Nikon Coolpix 4500 with a combination
of natural light and the Nikon Cool light SL-1. Higher
magnification images were taken with natural light using a Sony
CyberShot DSC-F 717 equipped with a combination of achromatic close-up
lenses (Nikon 5T, 6T and shorter focal length achromat) which screw
into the 58 mm filter threads of the camera lens. (These produce
a magnification of from 0.5X to 9X 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 717. (The magnification here is about 13X for a
4x6 inch image.) The photomicrographs were taken with a Leitz SM-Pol
microscope (using a dark ground condenser), and the Coolpix 4500.
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 June
2010 edition of Micscape.
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