A Close-up View of Arctic Jacob's Ladder


A Close-up View of Arctic Jacob's Ladder

Polemonium boreale 'Heavenly Habit'

by Brian Johnston   (Canada)

This hybrid of the Boreal Jacob’s Ladder species, (native to the high arctic and the east coast of Greenland), has purplish-blue flowers with brilliant yellow anthers on the ends of long filaments.  Unlike the native plant that has a very unpleasant smell, this one is pleasantly scented.  Probably because of its origins, the Jacob’s Ladder prefers cool, moist locations rather than hot, humid ones.

As you can see in the images below, the plant’s leaves are arranged ladder-like on each side of the stem, and this fact accounts for its common name.  A long, (30 centimetre) stalk holds the groups of flowers and buds above most of the plant’s foliage.

Most of the corolla of the flower is purplish-blue, but the centre is green.  Between these two extreme positions there is a bright yellow ring, and a reddish-purple ring.

New buds are encased by pointed, green sepals (modified leaves), and the enclosed petals are white at this point.

Several of the buds in the three images that follow are so young that no petals can be seen at all.  Almost all of the plant’s surfaces are covered with long woolly hairs; in other words they are pubescent.  Most of the buds are also sprinkled with bright yellow pollen grains.

Even the upper surface of a leaf has long hairs growing from it.  Note also, that the flower’s corolla has begun to unfurl at the top of the image.

One of the noteworthy characteristics of this species is the extremely large size of its anthers.  In some of the images, there appear to be one or two smaller anthers, but portions of them were obviously used as food by some insect.

The anther shown at the centre of the image below has as yet, not begun to release its pollen.

For comparison, here is an anther in which both lobes have split longitudinally to reveal the pollen grains hidden within.  (The process of an anther releasing its pollen is referred to as dehiscing.)

In the images that follow, notice the remarkable decrease in the size of anthers that are releasing pollen.  In addition, these anthers have a much more rounded shape than they had originally.

So many pollen grains are produced, that the structure of the anther is completely obscured!

A flower’s four-lobed stigma can be seen in the two images below.  Many bright yellow pollen grains cling to the receptive upper surface of each lobe.

Higher magnification reveals the rounded shape of each grain, and the many hair-like protuberances on the lobe’s upper surface that increase its surface area in order to maximize the acquisition and retention of pollen.

A side view of the pistil reveals the long purplish style that supports the stigma.

The two images that follow show a mystery that I can’t explain.  Why does this flower’s stigma have three lobes, while the others have four?  (The literature suggests that three lobes is “correct”, but who can argue with an actual specimen??)

Once a flower has been fertilized, its corolla, pistil, and stamens fall away, leaving only the ring of sepals surrounding a swelling ovary.

The arrangement of leaves on the main stem is rather fern-like.

A front view shows the ladder-like arrangement of leaflets, and the fact that each leaflet is connected directly to the stalk.

A reverse view shows that all of the leaflets face directly away from the stalk.

The single prominent, longitudinal vein on the back surface of a leaflet is evident in the two images that follow.

Although in an earlier image, the main stem appeared to have a circular cross-section, higher magnification shows that there are shallow ridges and depressions on its surface.

Jacob’s Ladder is a member of the Polemoniaceae, or Phlox family.

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.

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 2011 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 .