by Brian Johnston (Canada)
genus that belongs to the Crassulaceae
family. Members of this genus, native to the northern
store water in their leaves, and are thus referred to as
succulents. The species name reflexum
is from the Latin, and refers to the tendency of the
leaves to curve, or bend backwards.
The particular cultivar
here, called ‘Iceberg’, grows to about 30 centimetres in height,
has a very appealing colouration, with its lemon yellow flowers,
pale green leaves and stems. As can be seen in the first
the article, flower-heads have a ‘star-burst’ appearance.
images below show closer views of the flower-head.
The number of buds and flowers
this particular plant is simply amazing! Although small in
they make up for this deficiency with their elegant, muted
and striking shape. Buds and leaflets grow profusely along
radial stems of a flower-head.
The tightly packed yellow
buds peek out from between the seven, pointed, green sepals that
the flower’s protective calyx.
Buds near the ends of flower
often have a reddish tint to their sepals’ tips.
I thought at first that the
greenish-yellow object attached to a bud at the base of one of
sepals might be an insect, but it turned out to be an aberrant,
grotesquely distorted bud.
It is not only this
flowers that are beautiful; the mature buds are also!
The next stage to be looked at
the blooming process. As can be seen below, buds usually
from the centre of the flower-head out to its circumference, but
are exceptions to this rule.
As we move closer, the images
the flowers’ petals beginning to open to their final, almost
The sequence of images below
this process in more detail. Notice that the anthers
completely yellow at first, but soon begin to turn a light beige
Images taken from a different
show this difference more clearly.
Side views of a partially open
show that the sepals are fused at their bases.
The flower’s seven pistils are
difficult to distinguish because of their similarity in colour
base of the inside of the flower. Look for seven very
points in an almost circular array at the flower’s centre.
A photomicrograph of one of
pistils reveals that the stigma tip is just a continuation of
cone-shaped supporting style. Unlike in most other plants,
surface of the stigma appears to have no tiny lobes or hair-like
projections to catch passing pollen grains.
If the surface of a petal is
examined under the microscope, its cellular structure becomes
(third image). Note that Photoshop’s ‘Levels’ function was
to increase contrast and this results in the image being
The process of pollen release
anther (dehiscing) may begin before a bud is fully open.
image below, every other anther is dehiscing – a very, very
example, since the normal situation is completely random.
appears as though the immature anthers are covered by an
yellow green membrane, which dries and shrivels up to reveal the
brown dehiscing anther beneath.
An immature anther is much
in size than a mature, pollen releasing one. (Most of the
on the plant have 7 petals like this one. If you look at
previous image again, you will count 8 petals. Obviously
some variability! Usually members of this genus have twice
many anthers as they have petals.)
The first sign of imminent
disintegration is the appearance of brown areas on the
Below are photomicrographs
pristine membranes, and later stage ones.
The appearance of an anther
dramatically from the original bloated form, to the leaner
This stonecrop’s leaves grow
from lighter coloured cylindrical stems. Notice how most
back at their tips (reflexum).
Few stems that I have
have been as perfectly circular in cross-section as this
Notice that the leaves are without stalks.
Two images showing
through stems, reveal their internal structures.
If the entire plant is tilted
from the observer, one gets a view as though looking up from
the plant. The leaves are arranged alternately on the
as mentioned before, are stalkless.
While examining bits and
a flower under the microscope, I noticed a couple of interesting
things. Along the edges of petals, there are a number of
spaced glandular hairs with swollen tips.
One normally associates
guard cells with the underside of leaves, but those seen in the
below are from the green base of a petal. The very fact
base is green indicates that chlorophyll is present, and that
photosynthesis is occurring.
In the area where I live, lush
carpets of green grass cover the lawns of the majority of
Most homeowners take great pride in their ‘perfect’ lawns.
have seen my next door neighbour on his knees with nail
clipping errant blades of grass to the right height!) The
municipality has recently outlawed chemical weed-killers, and
suggested that some homeowners might do well to dig up their
and replace it with a front yard flower garden. I have
that the (very) few that have done so have many stonecrop
provide contrast with the colourful flowers.
The low magnification, (to
macro-photographs were taken using a 13 megapixel Canon 5D full
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
lens, the MP-E 65 mm 1:2.8, was used to take the remainder of
The photomicrographs were
using a Leitz SM-Pol microscope (using a dark ground condenser),
the Coolpix 4500.
A Flower Garden of
A complete graphical index of
of my flower articles can be found here.
The Colourful World
A complete graphical index of
of my crystal articles can be found here.
Microscopy UK or their contributors.
Published in the
January 2014 edition of Micscape.
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