A close up view of the columbine.

The elegantly shaped columbine with its long, distinctive spurs, exists as both wildflower and garden flower. Wildflower columbines (approximately seventy species), grow throughout the Northern Hemisphere in climates ranging from warm temperate, to arctic alpine. Their structure is unusual; other spur-bearing flowers such as impatiens, violets and larkspurs possess only one spur per flower, while the columbine has five!

This feature, coupled with the flowers’ attractive colouring and foliage, has spurred horticulturalists to develop many columbine cultivars. The subject of this article is a relatively new hybrid called Origami Red & White’, which flowers for the incredibly long period of three months! It also boasts resistance to hungry rabbits and deer! The plant grows to about thirty five centimetres in height, and the blooms are about eight centimetres in diameter.

Columbines are members of the buttercup family (Ranunculaceae). The common name is derived from the Latin word columba which means “dove”, or columbnus which means “like a dove”. This refers to the curved spurs which resemble (perhaps) a small clustering of the birds. By contrast, the genus name Aquilegia comes from the Latin word aquilinum which means “like an eagle”, since the aforementioned spurs look like the talons of an eagle. Obviously, the spur structures are interpreted very differently by observers. Doves are eagle food!

At an early stage of development, a columbine bud is enclosed by the green sepals (modified leaves) that will eventually turn red to form the outer ring of the mature flower, seen above.

Several days later, these sepals are tinged with pink, and the bud’s distinctive spurs have grown long enough to be clearly visible.

Many flowers have nondescript leaves, but I find those of the columbine to be particularly photogenic. Their finely veined, smooth edged, three-lobed structure is unusual, and quite striking.

The two photomicrographs shown below reveal a leaf’s cellular structure. The cells composing the lighter veins contain little or no green chlorophyll.

Notice in the following image, how the more deeply coloured, developing sepals seem to wrap around the base of each pale green spur.

Eventually, both the sepals, and spurs take on their final deep red colour. The only exception is the white tip of the sepal. Buds tend to face down, with the bulbous spur tips at the top of the structure.

As a bud opens to reveal the mature flower, it bends so that the floral tube is in a roughly horizontal position.

The reason for the columbine’s popularity is easy to see in the images below. The flower’s striking form and colouration are highlighted against a mass of bright green leaves. Note that the bloom’s inner ring is composed of five white edged petals, while the outer ring is formed by five bright red sepals.

Although a cursory inspection may give the impression that the five spurs are extensions of the red sepals, in fact, they are the extensions of the five white petals!

This is clearly shown in the image below.

Each of the flower’s spurs is a hollow, elongated tube which contains specialized cells that secrete nectar. The spur forms a reservoir for the nectar which collects in both the tube, and in the knob-like bulge at the tip. (The surface tension of the liquid holds it in these locations even if the flower is positioned at an angle where gravity would tend to cause the nectar to flow out of the spur.)

A closer view of the bulbous tips of spurs shows that they are translucent. Notice that both spurs and bulbs are covered with exceedingly fine hairs.

Under the microscope, the unusual colouration, and cellular structure of one of the bulbs are evident. The third image is taken at a much higher magnification than the first two.

Two photomicrographs follow that show the tube of a spur. The image on the right was altered in Photoshop by using ‘auto-levels’ to enhance contrast.

Notice the red sepals in the image below.

Under the microscope, the roughly spherical cells that form the sepal’s structure can be seen.

The surface of most sepals contains small imperfections. One such blemish can be seen at two different magnifications in the images that follow.

The cellular structure of one of the flower’s white petals can be seen in the photomicrograph below.

In certain lighting situations, the rough surfaces of both sepals and petals are evident. Notice that the base of each white petal transforms into the red tubular form of a spur.

When a flower first opens, each of its anthers (male pollen producing organs) is enclosed in an oval ‘anther cap’. The photomicrograph at right shows one of these caps. The image on the left also shows the light green filaments that support the anthers.

After a short time (several hours to a day), these caps disintegrate to reveal the yellow, pollen encrusted anthers beneath. In most flowers, this process starts at the centre of the cluster of stamens, and moves outward.

A photomicrograph of a pollen covered anther, and its supporting filament, can be seen below.

Two images of a filament follow. The image on the left uses normal dark-ground illumination. In the right image, the dark-ground condenser has been moved slightly off-axis to give a better impression of the three-dimensional character of the surface.

A higher magnification view of an anther reveals that columbine pollen grains are roughly ellipsoidal in shape.

Within the central area of the clump of stamens, there are many pale green, sharply tipped pistils, each of which is composed of a stigma (female pollen accepting organ), supported by a style.

The stigma tip can be seen below. It is unusual in that it has none of the hairy protuberances possessed by those of most other flowers.

On the other hand, the ovary, which is connected to the base of the short style, has many long hairs covering its surface.

Higher magnification reveals the hairs’ bulbous bottoms and thin tips. (The purple colour seen in the first image is an anomaly caused by using ‘auto-levels’ to increase contrast.)

The two images of an ovary that follow show the result of sliding the dark-ground condenser off-axis.

If the ovary is cut open, it can be seen to contain many egg-shaped, immature fruit.

The columbine’s structure has over time, evolved in order to control which pollinators can facilitate its reproductive success. In order to obtain the nectar stored in spurs, the insect or bird must have an appendage long enough to penetrate to the position of the nectar. Different species of columbine have different spur lengths, and this tends to ‘pick’ particular pollinators. Butterflies, hummingbirds, and even bees are possible pollinators for particular columbine species. As an insect’s or bird’s head is pushed into a spur to obtain the nectar, parts of its body come in contact with the mass of pollen covered anthers positioned above the spurs. When this pollen is then carried to another plant, cross-fertilization is accomplished.

Photographic Equipment

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 several images.

The photomicrographs were taken with a Leitz SM-Pol microscope (using a dark-ground condenser), and the Coolpix 4500.

Further Information

Columbines—Elegant Flowers Spurred to Greatness

http://www.bbg.org/gar2/topics/plants/2001sp_columbines.html

On Columbines

http://www.thecountycourier.com/index.php?option=content&task=view&id=2823&Itemid=

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