Close-up View of the
by Brian Johnston (Canada)
major, (Greater Masterwort, or “Hattie’s Pincushion” as it was
called in the past), is a member of the Apiaceae family. Since family
members have flower clusters in which each flower is joined by its
stalk to a common point, they are commonly referred to as Umbelliferae. Carrots,
parsley, and celery are edible vegetable members of the family, and so
is the extremely poisonous spotted water-hemlock – the most toxic plant
in North America.
Amazingly, Astrantia major has been cultivated
since the 1500’s. This is probably due to the fact that it is
very hardy, and produces seeds more freely than other species.
The plant’s leaves first appear in March, and its blooms appear late in
May. The name Pink Masterwort is used to describe the particular
hybrid photographed for this article.
The two images that follow show
what appears to be a group of flowers connected by their stalks to the
top of the main stem. Appearances can be deceiving! In
fact, each of the ‘flowers’ is not a flower at all, but instead a
flower-head composed of very many tiny flowers. What appear to be
the flower’s petals are actually a whorl of bracts surrounding the
cluster of real flowers.
During the late bud-stage of a
flower-head, the cluster of tiny buds is partly enclosed by these
petal-like bracts. Two of these early-stage flower-heads can be
seen near the bottom of the image below.
The side view that follows reveals
the dramatic changes in appearance of the flower-head as it
blooms. It is evident that the “Pink” in the common name Pink
Masterwort refers to the colour of the stalks supporting each of the
individual flowers in the cluster.
A very distinctive feature of the
species is shown below. Although the inner surface of each bract
is completely white, the outer surface displays a single, radial, green
vein with short branches along its length. Viewed from above, as
in the second image, the many unopened flower buds can be seen clearly.
The plant’s strong stem supports
many attractive green leaves, each of which possesses five palmately
arranged lobes with serrated edges.
Glossy green in appearance, the
upper surface of a leaf has an intricate vein pattern, and an edge with
tiny, needle-like projections as part of the serration.
The under-surface of a leaf is much
rougher, and is much lighter in hue. In fact, under the lighting
conditions of the photograph, it appears almost white, thus increasing
the contrast with the darker green vein structure.
Notice, in the image below, that
the lower of the two flower-heads is at a later developmental
stage. Not only is it larger, but out of each tiny flower there
project two hair-like stigmas.
At the point where the stalks of
the flower-heads join the main stem, there is a whorl of small,
These four leaflets can be seen in
the two images that follow.
Unlike the bracts surrounding the
flower-head, the leaflets have three parallel green veins, each with
many smaller off-shoots. The colour scheme of leaflets and bracts
Even the stalk supporting the
flower-head is unusual. Its shape is not cylindrical, but rather
cusp-like, with the channels a green colour, and the longitudinal
ridges a white colour.
Under the microscope, the cells
making up the surface and veining of a leaflet become visible.
photomicrographs showing the tip of a leaflet (left), and the underside
surface (right) can be seen below. Notice the prominent stomata
and guard cells that control gas access to the interior of the leaf’s
underside in the right-hand image.
As an Astrantia major flower-head
matures, its bracts flatten and open out to reveal the many flowers
within. These flowers mature from the centre of the group
outwards. This is indicated in the photograph by the emergence of
the hair-like stigmas and styles mentioned earlier.
Notice in the two images that
follow, the green tips of the bracts that frame the flower-head, and
their dark pink bases. The stalk of each flower is also pink.
Most of the flowers in the images
below are immature, but a few have their two stigmas and styles
protruding. If you look closely, you can also see five, white,
rod-like structures that curve from the periphery of the flower to its
centre. These are the stamens’ supporting filaments. (The
anthers are hidden within the body of the flower itself.)
A red anther, (male pollen
producing organ), and its supporting filament can be seen more clearly
in the photomicrographs below.
The cellular structure of the tip
of one of the flower’s two stigmas (female pollen accepting organ), and
its supporting style can be seen in the photomicrograph that follows.
If one removes some of a
flower-head’s bracts, and several of its flowers, the extraordinary
structure of an individual flower is revealed. Starting from the
bottom, each flower is supported by its pink stalk. The stalk is
connected to a strangely shaped, pale green, barrel-shaped ovary (seed
producing organ). At the top of the ovary are five tooth-shaped
sepals (modified leaves), each of which is dark green and has a pale
pink edge. Visible between these sepals are the five, paler pink
petals. Above these structures are the filaments, and in some
cases, the two pistils. (You may also notice that wherever the
filaments have been severed, a white, sticky liquid is exuded.)
An ovary like the one seen below,
which is positioned beneath the flower’s sepals and petals, is referred
to as inferior. The intricate structure of the ovary’s pale green
longitudinal ribs will be seen more clearly later in the article.
macro-photographs showing a flower’s outer whorl of green sepals, and
inner whorl of pale pink (almost white) petals can be seen below.
Very high magnification
macro-photomicrographs of the sepals and petals of a flower reveal more
details. (The whorl of green sepals is referred to as the
flower’s calyx, while the
whorl of petals is referred to as the flower’s corolla.)
Below are two photomicrographs
showing the cellular structure of the surface of the ovary. The
ridges take the shape of a meandering river.
photomicrographs follow that show the cells forming a section of the
Notice that at the very top of the
ovary, the ridges are tooth-shaped.
is native to Balkan coppices (thickets), and sub-alpine meadows.
Over many years it has been successfully trans-located to grow
in gardens almost everywhere. Its charms sadly, are not seen at
normal viewing distances. When viewed close-up however, its
spectacular, intricate structure is fully revealed!
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
The photomicrographs were taken
using a Leitz SM-Pol microscope (with a dark ground condenser), and the
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 March
2009 edition of Micscape.
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