Close-up View of a
by Brian Johnston (Canada)
Common mullein (Verbascum thapsis), the subject of
article, is an ubiquitous wildflower, and its tall woolly spikes,
covered with bright yellow flowers, are easily recognizable. I
thought that it might be interesting to take a photographic look at an
exotic relative produced by modern hybridization techniques. This
article is the result.
or mulleins as they are sometimes called, are native to the
Mediterranean region, but many have become naturalized throughout North
America. All belong to the Figwort family, (Scrophulariaceae). It is
believed that Mulleins have been grown as a garden flower since the
medieval period, and much work has been done to “improve” the lowly
wildflower, by judicious use of modern botanical techniques. One
such cultivar is the subject of this article, Verbascum hybridum ‘Caribbean Crush’.
Although the plant is undeniably spectacular, it doesn’t live up to the
developer’s original advertising, which stated that “the stalks are
covered with flowers that range from burnt orange to yellow or
mango.” In reality, all of the flowers on a stalk have exactly
the same colour! (It was ever thus!)
The tip of a 70 centimetre long
stalk can be seen below. Although in general, the flowers bloom
from bottom to top, there are exceptions. Unopened buds are
present both above, and below the flowering section.
As the buds mature, they change
colour from green, through yellow, to red. At an earlier stage
(farther up the stem), the extremely hairy, pointed green bracts
(modified leaves) that enclose the buds, predominate the view.
Even the under-surfaces of the
developing flowers’ bud-stage petals have a liberal coating of fine
As the buds mature, their stalks
grow longer. Notice in the image at left, that very immature buds
are mixed in with their older siblings. Near the top right of the
image on the right, a flower has completed blooming, and all that
remains is the long pistil ringed by sepals.
At the centre of the image below,
note the pointed shape of an early stage bud.
Notice in the two images that
follow, how the flower’s petals are folded over one another in an
almost random manner, with each bud showing a different fold pattern.
Here are several images that show
the purple style, and green stigma that remain after the petals of a
flower drop off. Once a flower has bloomed, this petal-drop
happens extremely easily. The slightest touch of the stem
produces an alarming shower of petals – (alarming to the person trying
to photograph “perfect” flowers that is!)
The image below shows a bud with a
pentagonal shape, about to blossom.
Buds in the process of opening can
be seen in the lower portions of the two images that follow.
Multiple stems grow from the
plant’s base. Notice the different flowering pattern exhibited by
Once opened, the five-petaled, 2.5
centimetre diameter flowers are revealed.
If the base of one of the flower’s
petals is examined under the microscope, a variety of pigmented, and
unpigmented cells can be seen.
On the underside of a petal, hairs
grow from the surface.
The surface (epithelial) cells of a
petal are almost spherical in shape. (Adobe Photoshop’s “Auto levels” function was used on
both images to increase contrast. This accounts for the false
A higher magnification view of a
petal’s underside shows that the hairs growing from its surface are
branched. Contrasting with these hairs, are the ones growing
along the edge of the petal, some of which have glandular protuberances
at their tips.
The three images that follow show
views of the flower’s strange reproductive structures which consist of
a single pistil, and five stamens. In this species, three of the
stamens are smaller, and are fringed with long white hairs, while two
are larger, and are less hairy.
The distinctive differences between
the two types of stamen can be seen clearly in the higher magnification
image that follows. The three smaller anthers, (male pollen
producing structures), have a yellow base, and a brownish-red
edge. Immediately beneath each anther is a dense fringe of white
hairs. The lower two anthers are larger, and are missing the
hairy fringe. If you look carefully however, you can see that the
red filaments supporting the anthers have their own white surface hairs.
All of the white hairs mentioned
above have bulbous tips. Those on the filaments tend to have red
bulbs, while those on the upper anthers tend to have white bulbs.
Three images showing filament hairs can be seen below.
As the hairs age, they tend to
become ribbon-shaped, and have the random, twisted appearance seen on
Below, on the left, is a
photomicrograph that shows the darker coloured band at the edge of an
anther. The higher magnification image on the right shows the
cellular structure of an anther’s surface.
Several hairs from an anther’s
fringe can be seen below. The colouration doesn’t appear white
because the light from the dark-ground condenser has been coloured by
passing through the anther itself.
The four images that follow show
different views of a flower’s pistil, consisting of a red
supporting style, and green stigma (pollen accepting organ). In
this species the stigma has a flattened oval shape, with a distinctive
groove on its upper surface.
Under the microscope, this groove
can be seen clearly. Notice that the stigma’s entire surface is
covered with tiny, hair-like protuberances.
These protuberances are easier to
see in the higher magnification images that follow. Their purpose
is to increase the effective surface area of the stigma, and aid in the
retention of pollen grains carried to the flower by visiting insects
Like the common mullein, this
hybrid has intensely hairy leaves, and this causes them to feel downy
soft to the touch. The lighter coloured veins on the leaves’
lower surfaces gives them a very attractive appearance.
The leaves are stalkless – they
grow directly out of the main stem. Note that the stem is also
covered with short, soft, white hairs.
In contrast to the lower surface,
the upper surface of a leaf has far fewer hairs, and in the right
light, appears shiny.
Closer views of the bottom of a
leaf reveal that every part of the surface is hairy.
The two images that follow show the
segmented nature of the hairs growing along a leaf’s edge.
If the hairs growing from the veins
on the under-side of a leaf are examined, they appear to branch, and
have pointed tips.
Much shorter, glandular hairs, that
end in bulbous tips, grow from a vein’s surface. The image on the
right shows their circular top when viewed from above.
The striking flowered spikes of Verbascum hybridum ‘Caribbean Crush’
make this plant a popular garden choice. Like its lowly relative Verbascum thapsis, it does best in
poor, dry, rocky soil. When watered or fertilized too much, it
grows poorly. What more could a gardener ask for?
All of the macro-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. A Canon 250D
achromatic close-up lens was used to obtain higher magnifications in
The photomicrographs were taken
with a Leitz SM-Pol microscope (using a dark ground condenser), and the
A search for “Verbascum information” using Google results in a wealth of info,
both on the wildflower, and hybrid species.
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 July
2009 edition of Micscape.
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