Close-up view of a hybrid Cymbidium


A Close-up View of a Hybrid

Cymbidium Orchid

by Brian Johnston   (Canada)

Cymbidium orchid hybrids are grown in huge numbers to supply the cut-flower trade.  Their long spikes, containing many large, brightly coloured flowers, often continue to bloom for two to three weeks.  They are also one of the most popular flowers for use in corsages.  Of course, many Cymbidiums are available for use in outdoor landscaping, provided that one lives in a suitable climate.  No one would describe them as “shrinking violets”, since these large, grassy orchids may have spikes up to a metre in length, and blooms over 10 centimetres in diameter.

The natural habitats of this genus are widespread, from mid-Asia through southeast Asia to Australia and New Zealand.  Wild Cymbidiums may be terrestrial, meaning that they grow in well drained ground locations, epiphytes, where they cling to trees, or lithophytes where they cling to rocks.  Presently, most of the Cymbidium plants available to the public are semi-terrestrial, and are grown in greenhouses under carefully controlled conditions in order to maximize their success rate.

Cymbidium, the genus name, is derived from the Greek word kymbe which translates to boat.  This refers to the hollow recess in the lip, or labellum of the flower.

The Cymbidium spike (or raceme) shown below is about 50 centimetres in length, and contains thirteen flowers.  Its stem is extremely sturdy, making macro-photography a pleasure.

In the spikes of other plants, the flowers are usually oriented identically on the stem.  In this case however, note that many of the blooms are not perfectly horizontal, and that one faces up.

Stems lack the small leaflets that are frequently seen in other genera.  In my plant at least, all of the blooms are positioned on one side of the stem.  The almost parallel, green veins that are visible on the back of the flowers’ sepals, are less prominent on their front surfaces.  In the image on the right, the uppermost section of the flower’s stalk possesses noticeable ridges, and has a slightly larger diameter.  This is the flower’s ovary.

Orchids normally possess an outer whorl composed of three sepals (modified leaves that protect the flower’s bud stage), and an inner whorl of three petals.  Two of the flower’s three petals are indistinguishable from the sepals .  The third petal is grotesquely transformed into the flower’s distinctive, red-coloured trumpet.  This unusual structure is called the labellum or lip.

The labelled image below shows the main parts of the Cymbidium’s reproductive system.  At the centre of the flower is a roughly cylindrical projection called the column.  (In this hybrid the cross-section is actually more oval than circular.)  This column, (sometimes called the gynandrium or gynostemium), contains the male anther and female stigma.  Covering the end of the column is the white anther-cap which will be discussed later.  For fertilization to take place, an insect must land on the labellum, climb into the throat, and up onto the strangely tongue-like yellow platform beneath the column.  From this position it may dislodge the anther-cap to obtain access to the pollen masses of the flower, or it may come into contact with the stigma.

Both sepals and petals are fleshy, waxy, and almost translucent in bright light.  Only the top, banner-like sepal is rounded at its tip.  All of the other sepals, and the two wing-like petals are pointed at their tips.

The trumpet-shaped labellum is the most colourful structure of the flower.  The intricate pattern on its surface probably evolved as an insect attractant.  The image at right below shows a highly magnified view of the labellum’s surface.  The yellow “dust” near the edge is pollen.

Two very high magnification macro-photographs show this pollen more clearly.  In the image on the right, individual pollen grains can be resolved.

The labellum’s surface is covered with many rod-like, almost transparent hairs that are concentrated in the areas of the red spots and lines.

At the very edge of the labellum, a slightly different type of hair can be seen.  Many of these are larger, and have a more rounded tip.

Immediately under the anther-cap there is a tongue-shaped structure covered by an extremely large number of fine, semi-translucent hairs.

A view of the very tip of the tongue shows just how closely these hairs are packed on its surface.

The bulbous tips of the hairs suggest that they are glandular in nature.  Six images with increasing magnification show the details of these glandular hairs.

As you can see below, the entire top surface of the “tongue” is completely covered by hairs.

The underside of the “tongue” however, has none.

Immediately behind the “tongue” in the image below is the “front” of the orchid’s column.  It is yellow and pink in colour, and is covered with dark red spots.

The two macro-photographs below show the column’s surface near its base.  The surface appears shiny, as though coated with liquid (nectar?).

Higher up the column, the background colour transitions to pink, and the round spots become oval.

Much higher magnification of these oval spots reveals interesting details.

The time has come to take a closer look at the orchid’s reproductive structures.  The tip of the flower’s column curves down towards the labellum.  This forms a sort of hood under which the anther and stigma are located.

In the images below, the white anther-cap can be seen to be divided into two almost spherical lobes by a groove.  On each side of the cap there is an arm-like projection growing from the column.  These “arms” may help to strip the pollen mass from a visiting insect.

In order to see the structures more clearly in the images that follow, the column has been removed from a flower.  Notice that from this angle, the anther-cap looks remarkably like the head of an albino bird – beak and all!  In order for an insect to obtain access to the flower’s anther and pollen masses, it must lift (or push) the beak upwards.  The entire anther-cap will then be dislodged, and the cap will fall away, revealing the flower’s pollen masses.  Under the beak in the first image, there is what appears to be a white envelope-like structure that is slightly open at the front.  The interior of this structure is the flower’s stigma. 

A much higher magnification reveals the strange surface appearance of the lobes of the anther-cap.  Each cell appears as a transparent liquid droplet!  The white structure beneath the anther-cap, as mentioned before, is the upper surface of the stigma chamber.

Notice below, that the red material that constitutes the end of the column wraps over the anther-cap like the shoulders of a coat.  Remember that there is no connection between the “coat” and “cap”; an insect can easily dislodge the cap.

Here is what the column looks like after the anther-cap’s removal  The two bright yellow mounds are the flower’s two pollen masses (pollinia) – looking remarkably like poached eggs!  These packages of pollen are sticky, and when an insect comes into contact with one of them, all or part of the pollen mass adheres to a leg or part of its body.  If we move under the column shown in the first image, and look up, we see the shiny receptive surface of the flower’s stigma.

Incredibly, the Cymbidium orchid was written about in China and Japan before the time of Confucius (551-479 BC).  Today, due to the ongoing efforts of horticulturists, these large, spectacularly colourful  flowers are ubiquitous.

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.

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 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.

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Published in the November 2010 edition of Micscape.
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