A (second) close-up view of the teasel, Dipsacus fullonum


A (Second) Close-up View of the


Dipsacus fullonum

by Brian Johnston   (Canada)

Spectacular because of its large, unusual, egg-shaped flower-head, and its one to two metre height, the teasel certainly stands out in the landscape.

Like other wildflowers, the plant is known by many names.  Dipsacus, its genus name is derived from Greek, and means ‘to thirst’.  This refers to the fact that rainwater collects in a bowl-like structure at the point where each basal leaf joins the main stem.  For this same reason, the Romans called the plant ‘Venus’s basin’, and the early Christians in Ireland referred to it as ‘Mary’s basin’.  Teasel’s species name fullonum refers to the occupation of a fuller, someone who used the dried flower-heads to comb the tangles from wool.  Thus ‘Brush and comb’, and ‘Fuller’s herb’ are other common names for teasel.  Another name, ‘Johnny-prick-the-finger’ refers to the plant’s defensive array of formidable prickles, or spines.

Teasels belong to the family Dipsacaceae.  Although their flowers appear similar to other composite flowers, there are technical reasons for considering them separately.  One of these is the fact that in a composite flower, the edges of stamens are packed together forming a cylinder around the style. In a teasel flower however, the stamens are separate from one another.

The first image in the article shows a typical flower-head in bloom.  Notice the long, leaf-like bracts that branch out from the base of the flower-head, and curve up artistically around the bloom.

The following two images show a flower-head in the ‘bud’ stage.  The developing buds are well protected by the tightly packed array of extremely stiff, sharply pointed bracts that resemble bristles or spines.  Notice that these bracts are relatively short near the flower-head’s base, but increase in length near its apex.

As is evident from the following sequence of images, the flower-head begins to bloom in a ring around its middle.  Later, as we will see, the most central of these flowers will die and two separate rings will continue to bloom, one moving up towards the apex, and one moving towards the base.  Although individual flowers are difficult to see at this magnification, their anthers, which extend out some distance from the flowers themselves, are easily discernable.  In total, there are approximately 2000 flowers in each flower-head.

A closer view of the base of a flower-head shows the top of the plant’s stem, and the ring of upward curving bracts.

Carrying a teasel plant home from the ‘wild’ is not an easy task.  Its stem is covered by extremely tough, sharp spines.  Even getting a grip on the plant in order to cut through the stem is very difficult.  (I usually hold the stem with pliers while cutting it, and then transfer the stem to a cardboard paper towel tube for the trip home.)  Notice that the spines grow along the light coloured ridges that run the length of the stem.  Between these ridges are pale green, spineless grooves.

The images that follow show the rings of green bracts that grow from the top of the stem.  Several rings are visible, with the outer ones being longer than the inner ones.  The lower surfaces of these bracts are sparsely covered with spines.

Much closer views of a bract can be seen below.  Notice that individual spines are white in colour, and thus they contrast with the green of the bract.  Closer examination reveals that the edges of a bract are white or light brown in colour.

Near the base of the flower-head, the bristles are about the same length, or shorter than the flowers.  Although the bristles are green at their bases, they are brown just beneath the tips, and white at their tips.  The first image shows anthers and filaments growing out from the flowers’ pale, purple-tipped tubular corollas.

Near a flower-head’s apex, these bristles are longer, and brown from base to tip.  Notice the orange globule of insect ‘spit’ adhering to the side of one of the bristles.

The three images that follow show the pale green unopened flower buds, and their associated bristles.  The second image shows the long, transversely curved shape of the bristles.

Views looking down onto the top of a flower-head appear at right, and on the next pages.  Notice that the dome-like buds nearest the ring of blooming flowers have a deep pink tint, while those farther away are less deeply tinted.

The images that follow show buds that are about to bloom.  In the first three, notice that the light purple corollas of individual flowers are visible.

As was mentioned earlier, the flowers in the central ring soon shrivel and fall from the flower-head.  This leaves many empty sockets which can be seen in the image below.  Upper and lower rings continue to bloom.

Four images follow that reveal the top of the egg-shaped flower-head at this point in the blooming process.  Notice in the last image, how far each flower’s stamens protrude beyond the corolla.

Macrophotographs showing the lower section of the same flower-head reveal different bud tints that indicate their order of opening.

As one moves up the magnification scale, the flowers’ stamens, consisting of pale purple anthers and colourless supporting filaments, become easier to resolve.

By choosing appropriate viewing angles, and by using still higher magnifications, the structure of individual teasel flowers can be seen.  Each flower consists of a tubular corolla 10 to 15 mm in length which is almost white near the base, and pale to deep purple near its four-lobed end.  Four stamens protrude from each flower, and as can be seen in the third image, so does a single white pistil.

Photomicrographs of the stigma, and stocky supporting style can be seen on this page.  Notice the almost spherical pollen grains clinging to both stigma and style.  In the first two images, note how much greater the diameter of the style is than that of a filament.

One lobe of the four-lobed corolla is larger and longer than the others.  The corolla tube does not appear smooth at this magnification.

The reason for this rough appearance can be seen in the four photomicrographs that follow.  These show the cellular structure of the corolla lobes.  Notice that some of the cells near the edge of the corolla lobes are much larger, and have a rounded cylindrical shape (first two images).  Others on the surface of the lobes have a stubby hair-like appearance (last two images).

As we get closer and closer to the flower-head, the liberal coating of pollen grains on the surface of anthers becomes visible.  At the limit of the magnification possible with my equipment, the spherical shape of the grains is evident.

Under the microscope, the oval shape and colouration of an anther can be discerned.

Still higher magnification shows that pollen grains have a barrel shape rather than a perfectly spherical one.  As well, tiny protuberances are visible on a grain’s surface.

Different illumination shows that the upper surface of the anther is completely covered by pollen grains.

Extremely tiny, downward pointing hairs cover the surface of a supporting filament in the high magnification photomicrograph at right.

Beneath the flower-head, several leaves can be seen growing from the stem.  Notice that they are stalkless and are arranged opposite one another.  Each leaf tapers towards its ends.

If the under-surface of a leaf is examined using the microscope, the oval stomata and guard cells that control gas entry into and out of the leaf are clearly visible.  Several bulbous glandular hairs can be seen growing from the colourless leaf veins.

While taking the previous photomicrographs, I detected motion in the field of view.  Closer examination revealed numerous sucking insects on the leaf’s upper surface.  Notice the dark, almost black spots within each insect’s body.

The upper section of the teasel’s stem is divided into two sections at the junction point of the leaves.  Notice the smaller diameter of the upper section, and its darker colouration, with fewer ‘prickles’.

Beneath the junction point, the colourless spines, and speckled brown longitudinal bands on the stem are visible.

Teasel is a biennial plant that lives for two years.  During the first year only a basel rosette of ground hugging leaves reveals its presence.  In the second year, a long stalk is sent up which branches to hold numerous egg-shaped flower-heads.  During the autumn of the second year the plant dies, and the stem, leaves, and flower-heads turn a brown colour.  Both the stalks and flower-heads persist through the winter, often projecting up through the snow in a very attractive display.  The plants seen below were photographed in late August, and had begun the transformation to brown.

Closer views reveal that the stems retain their green colouration longer than the empty flower-heads.

In addition to being used historically in the textile industry, dried teasel flower-heads were utilized as bizarre ornaments in winter flower arrangements.  In New England they were even used by rural housewives to sprinkle water on clothes before ironing!

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.

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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