A close-up view of Roma Masterwort


A Close-up View of Roma Masterwort

Astrantia major 'Roma'

by Brian Johnston   (Canada)

Astrantia major, (“Greater Masterwort”, “Hattie’s Pincushion” or “Melancholy Gentleman”), 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 strangely, 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 flowers appear late in May. The cultivar name Roma Masterwort is used to describe the particular hybrid photographed for this article, which has particularly colourful blooms.

The first image in the article, and the one that follows, show the most colourful aspect of  Roma Masterwort.  What appear to be the flowers’ petals, are not petals at all, but whorls of protective bracts (modified leaves) surrounding each composite flower-head.

These pinkish-red bracts display a complex vein pattern when viewed close-up.  At this early stage of the blooming process, the actual flowers are not visible in side views of the plant.  As the plant grows, the stalk supporting each flower-head grows in length. The last three images of the group show immature flower-heads that are still enclosed within groups of green leaflets.

A view of what is hidden within the whorl of bracts can be seen below. Each of the red pentagonal structures is an individual Greater Masterwort flower.

The two images that follow show how the bracts open out until they form an almost flat surface as the flower-head blooms.  Notice that the bracts are lighter in colouration on their inner surface.

The many individual flowers whose stems grow from a common disk in the centre of the whorl of bracts, reach maturity in order from the centre, to the circumference.

Viewed from the back, the whorl of bracts is very visually appealing.  Each bract possesses a longitudinal, green central vein, with a less prominent, lighter green vein on each side.  A finer pattern of veins interconnects these more prominent ones, and continues out to the bract’s edge.

Closer views of the upper surfaces of flowers show their pentagonal shape, and several projecting structures.

Beneath each pinkish-red flower is a ring of tiny, dark green sepals, and beneath the sepals is a pinkish-white, barrel-shaped ovary.

Two white-tipped pistils extend out of the flower in a V-shape.  Each sturdy, red style supports a white stigma.  Just to the left of the two pistils in the image is one of the flower’s five stamens, comprised of a red filament which supports a white anther.

If some of the flowers are removed from the flower-head, it is easier to see the arrangement of its constituent parts. A flower’s stalk grows from a disk at the top of a ridged stem.  The top of the stalk connects to the flower’s ovary.  Growing from the top of the ovary is a single whorl of five dark green pointed sepals.  These sepals surround the five pink flower petals.

Details of the ridged stem, and convex green dome from which the flower stalks grow can be seen clearly in the image that follows.  Note that when each flower’s stalk is cut, a milky liquid is exuded.

An ovary which is positioned beneath a flower’s sepals and petals is referred to as inferior.  Notice the striking intricate structure of the ovary’s pale green, to light pink, longitudinal ribs.

Associated with each sepal is a curved pink rod.  The pink rod is actually a filament, and it supports an anther buried deep within the flower.

Much closer views of a flower reveal more details.  The whorl of sepals, each of which is green at its base, and pink at its sharply pointed tip, is called the flower’s calyx.  The whorl of pink, heart-shaped petals is called the flower’s corolla.  If you look closely, you can see the almost white oval anthers which are connected to the thin ends of filaments.  Projecting out of the flower are its two pistils.

Notice that the ridges on the ovary’s surface have pointed, scale-like projections, and that between the bands of ridges, the inner pale green surface of the ovary is visible.

After several days, the whorl of bracts enclosing the flower-head has opened out into its final, almost horizontal position.

Various stages in the blooming process can be seen in the three images that follow.  Notice that the inner portion of the open whorl of bracts is almost completely white.  This may provide contrast for the colourful flowers, and help visiting insects in navigating to the flower-head’s central area.

At the point on the main stem from which the flower-head stalks emanate, there is a ring of three distinctively shaped leaflets.

Two notches near the top of an essentially oval leaf produce the three-pointed shape.

The lower and middle portion of one of these leaflets can be seen below.  Notice the very three-dimensional veining on the lower surface.

Higher magnification shows these veins more clearly, as well as the very tiny pink, hair-like spines along the leaflet’s edge.

Lower on the stem, immature leaflets overlap, and sheath the stalk.

While photographing the plant’s stem, I noticed motion through the camera’s viewfinder.  An extremely small sucking insect was exploring the landscape.  It was kind enough to remain stationary long enough to obtain the following images.

The stem itself is unusual.  Its shape is not cylindrical, but rather cusp-like, with the channels a green colour, and the longitudinal ridges a white colour.

Greater Masterwort leaves possess five palmately arranged lobes with serrated edges.  The image reveals that each of the lobes has a slightly different shape.  They are certainly not carbon-copies of one another!

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 the same leaf is rougher, and much lighter in hue.

Astrantia major 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!

Photographic Equipment

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.

A 10 megapixel Canon 40D 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 images.

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.

  All comments to the author Brian Johnston are welcomed.

Microscopy UK Front Page
Micscape Magazine
Article Library

© Microscopy UK or their contributors.

Published in the September 2010 edition of Micscape.
Please report any Web problems or offer general comments to the Micscape Editor.
Micscape is the on-line monthly magazine of the Microscopy UK web
site at Microscopy-UK  

© Onview.net Ltd, Microscopy-UK, and all contributors 1995 onwards. All rights reserved. Main site is at www.microscopy-uk.org.uk with full mirror at www.microscopy-uk.net .