A Close-up View of the Chinese Pagoda Primrose


A Close-up View of the

Chinese Pagoda Primrose

Primula vialii 'Chinese Pagoda'

by Brian Johnston   (Canada)

“Her mist of primroses within her breast
Twilight hath folded up, and o’er the west,
Seeking remoter valleys long hath gone,
Not yet hath come her sister of the dawn”

George William Russell
(1867 – 1935)

This Primula vialii hybrid certainly looks different than other Primroses!  Perched atop a long cylindrical stem, its two-toned, rocket-shaped flower-head has brilliant red bracts, and orchid pink flowers.  The plant grows to about 40 centimetres in height, and has a rosette of short, unusually shaped basal leaves.  Other common names for this species include Foxtail Primrose, Poker Primrose, Orchid Primrose, and Wayside Primrose.

The Primula genus of perennials contains around 400 species, most of which are found in the Northern Hemisphere temperate regions.  China and the Himalayas possess the greatest number of species, and Primula vialii is in fact native to China’s Yunnan Province.

Images follow that show the plant’s long stem, and two-toned flower-head.

Most leaves in the basal rosette are positioned vertically, and thus show their ‘back’ surface to the observer.

The ‘front’ of a leaf is intensely hairy and possesses a central longitudinal vein with irregularly positioned offshoots.

As can be seen below, each leaf has an extremely concave ‘back’ surface, and strikingly toothed margins.

The two images that follow show the white ‘peg’ that forms the tip of each tooth along a leaf’s margin.

Notice in the image at left below, how prominent is the main vein on a leaf’s underside.  It is also extremely hairy.  The photomicrograph on the right shows one of the teeth along the leaf’s margin, and the bulbous-tipped glandular hairs that grow from its surface.

The cellular structure of one of the ‘pegs’ at the tip of a tooth can be seen in the image on the right below.

Stomata and guard cells, which control gas entry and exit from a leaf’s underside, are visible in the photomicrograph below.

Photomicrographs follow that show the segmented glandular hairs that grow from the veins on the underside of a leaf.

Viewed from directly overhead, the glandular hairs appear as shaded spheres.

A leaf’s main vein is not imbedded deeply in the undersurface of the leaf, but is very prominently raised, with minimum connection between vein and leaf.

The plant’s main stem has an approximately circular cross-section, with a single, shallow longitudinal groove on its surface.

Closer views reveal that the stem is also liberally covered with short glandular hairs.

The following sequence of images, taken with increasing magnification, shows a very early bud-stage flower-head.  At this point the buds are still completely protected by pale green bracts, (modified leaves).  Near the tip of the flower-head, hints indicating the eventual red colour of the bracts have begun to appear.

A week later, these same bracts are brilliantly red coloured on an almost white background.  At this stage, no signs of the underlying flower buds are visible.

At the middle of both images below, you can see the purple tips of bud petals peeking out from between the bright red bracts.

If the surface of one of the bracts is examined under the microscope, its cellular structure becomes visible.

Higher magnification reveals more detail.

While working with the plant, I noticed that most of the structures comprising the flower-head were covered with what appeared to be microscopic ‘snow flakes’.  Under the microscope, these appear to be tufts of white fibrous material whose purpose is unknown.

The three images that follow show the flower-head in bloom.  Flowers have five pink, pointed petals fused at the base to form the corolla.  At the centre of each flower, there is a group of yellow anthers.  Note that the top of the stem has been angled away from the viewer in order that he or she can see into the recesses of the corollas.  Normally, the flowers are angled downwards, preventing the reproductive structures from being seen.

This normal orientation can be seen in the images below.  Note that each flower is attached to its stalk through the narrow tubular base of the flared corolla.  In many images, the pure white tufts of fibrous material mentioned earlier can be seen coating the inner surfaces of corollas.

The cellular structure of the outer surface of a petal is visible in the photomicrographs below.  Note the variable shape of pollen grains in the second image.

Closer views of the ring of anthers at the centre of each flower’s corolla can be seen in the images that follow.  Some flowers possess six anthers, while others appear to have only five.

The image that follows on the left shows a portion of the tubular base of a flower’s corolla.  A dark shadow is being cast by some internal structure.  The image on the right shows this structure – an anther joined to the wall of the corolla by a short, remarkably small diameter filament.

The final views show more highly magnified anthers with their variably shaped pollen grains.

The hybrid Primrose studied in this article, Primula vialii ‘Chinese Pagoda’, was awarded the Royal Botanical Society ‘Award of Garden Merit’ in 1993.  It is indeed a spectacular plant!

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 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.

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

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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