View of a Hybrid Foamflower
by Brian Johnston (Canada)
The Saxifrage Family (Saxifragaceae) of
which Foamflower is a member, contains about 700 species.
Tiarella cordifolia has flower
stalks covered with delicate,
star-shaped flowers sprouting very long stamens. These stamens
are so numerous, that it appears as though the flower-head is
surrounded by a yellowish-white cloud – hence the common name
Foamflower. The plant is diminutive, with its multiple
flower-heads reaching a maximum height of only 30 centimetres.
plant’s genus name,
comes from the Greek word tiara.
this meant “turban”,
a reference to the shape of the plant’s fruit. (Other sources
contend that it was the shape of the flower’s pistil that resembled a
turban.) The species name cordifolia
means “heart-leaved”, a
reference to the shape of its leaves. Although the leaves do
appear heart-shaped, a better description might be that they resemble
rounded maple leaves. In addition to being called ‘Foamflower’,
the species is also referred to as ‘False Miterwort’, ‘Cool wort’ and
The image above shows a group of
Foamflower flower-heads. Although a flower’s petals are white,
its bright yellow anthers, and rust-coloured unopened buds give the
flower-head an attractive appearance.
Foamflower is a clump forming
perennial which spreads by sending out runners (stolons) to form a
colony. One such colony can be seen in the images that
follow. Notice that young leaves have a coppery colouration that
soon transforms into the normal green.
The stem immediately beneath the
flower-head is leafless. Note that as you go up the stem, the
distance between the flower stalks decreases, producing a very dense
packing of flowers near the flower-head’s tip.
Two bud-stage flower-heads are
visible in the image below. Both are cone-shaped, and both are
extremely small at this stage – less than one centimetre in length!
Higher magnification views show
individual flower buds. Each bud is protected by a single whorl
of five, pointed sepals which are fused together at the flower’s
base. This whorl of sepals is referred to as the flower’s
calyx. In several buds, it is possible to see between the sepals,
and the flowers’ petals are visible. Strangely, they appear
orange, rather than the white of blooming flowers.
In the images that follow, the two
bud-stage flower-heads seen earlier have begun to bloom. The
process occurs from bottom to top.
Notice in the image below, that as
a bud opens, its sepals change colour to a pale off-white. It is
also apparent that the assumption that the underlying petals were
orange was incorrect. The orange colour is actually the colour of
the anthers, not the petals. Finally, notice the long white
pistil that protrudes from the newly opened bud.
Although a mature flower has many
white petals, closer examination reveals that the “petals” come in two
distinct shapes. In fact, the broader, shorter ones with little
narrowing at their bases, are sepals. Between each pair of sepals
is a longer, narrower structure held by a very thin stalk. This
is an actual petal. The flower’s whorl of five petals is referred
to as the corolla.
Additional views of blooming
Foamflower inflorescences follow.
Examination of the opening bud just
to the left of centre in the image below, reveals the unusually large
size of its yellow-orange anthers compared to the bud itself.
If one of a flower’s sepals is
examined under the microscope, its edge is seen to have many
bulbous-tipped (glandular) protuberances.
An opening flower can be seen in
the two images below. Notice in the image on the right, that the
outer surface of a sepal is covered by the glandular hairs mentioned
above. Also note the pale green, swollen ovary at the flower’s
To begin, each of the flower’s
anthers is protected by a yellow-orange, thin membrane.
Eventually, the membrane dries, its surface cracks, and it falls away
to reveal the anther’s pollen grains.
Photomicrographs showing membrane
covered anthers can be seen below.
If you look carefully at the area
just to the right of centre in the image that follows, you will find
the very fine tip of the flower’s pistil. In this species, the
broad base of the style narrows to a fine point at the stigma that it
Photomicrographs showing the
flower’s stigma can be found below. Notice that many glandular
hairs cover its surface which increase its surface area, and thus aid
in the acquiring and retention of pollen grains.
The two photomicrographs that
follow show a flower’s ovary. Notice that it too is covered with
glandular hairs. The surface has been deliberately punctured to
allow a view of its contents. The ellipsoidal structures within
the ovary are immature seeds.
Let’s take a closer look at the
leaves of the Foamflower plant. As mentioned earlier, immature
leaves have a coppery colour that soon changes to bright green.
Front and back surfaces of a mature
leaf can be seen below. Each leaf has a long stalk, (or is
long-petioled), and is broadly heart-shaped, somewhat like a rounded
maple leaf. The back surface of the leaf has many prominent
A closer view of these veins
reveals that they are covered with fine, soft hairs.
Even the leaf’s upper surface
displays hairs, but they are less densely packed here.
Glandular hairs positioned along
the edge of the upper surface of a leaf can be seen in the two
photomicrographs that follow.
Similar hairs are visible growing
from the veins on the leaf’s underside.
Finally, here is an additional
assortment of images of this interesting hybrid, Tiarella cordifolia
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
The photomicrographs were taken
using a Leitz SM-Pol microscope (using a dark ground condenser), and
the Coolpix 4500.
A Flower Garden of
A complete graphical index of all
of my flower articles can be found here.
The Colourful World of
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of my crystal articles can be found here.
Microscopy UK or their contributors.
Published in the
December 2009 edition of Micscape.
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