View of a Flowering Begonia
Begonia x hybrida
by Brian Johnston (Canada)
For the botanical layman, Begonia plants
are relatively easy to identify. Their fleshy jointed stems,
showy flowers, and distinctive asymmetric leaves set them apart from
other genera. Unfortunately, an unusual characteristic of
Begonias is that species throughout the genus can be hybridized with
one another, even if they originated on different continents.
This might seem like a good thing, but it has resulted in a huge number
of cultivars to be developed worldwide. Distinguishing between
these hybrids is a formidable task, and so for the purposes of this
article, I will simply consider my plant as a ‘typical Begonia’.
Both its common, and genus names were suggested by Charles Plumier, a
French patron of botanical research. Begonia and Begonia honour Michel Begon, a
former governor of the French colony of Haiti.
In fact, the subject of this
article was in rather ragged condition when I spotted it in the
‘marked-down’ area of the greenhouse. Since it was the only
Begonia in bloom at the time, I decided to take a chance and bring it
home, in the hope that it would survive until I finished photographing
The first image in the article
shows the plant’s deep green leaves, and multiple flower-heads.
Below are two images showing Begonia flowers - flowers that are
distinctly different in shape than those of most other plants.
Begonias are monoecious, meaning that they have
separate male and female flowers on the same plant. Male flowers
are referred to as staminate,
while female ones are called pistillate.
of the flowers shown in the two images below are pistillate, as
revealed by their three bi-lobed stigmas. It appears as though
each flower possesses two petals, but in this genus sepals and petals
are indistinguishable, and so both are referred to as tepals.
One of the stems supporting a group
of flowers can be seen in the two images that follow. The many
pale green tri-lobed structures are the ovaries of pistillate
flowers. Note at the very top of the stem, several oval leaflets
which have no connecting stalk. Such leaflets are referred to as ‘clasping’.
These clasping leaflets occur only
in the top-most section of each of the plants stems.
Closer views of a leaflet reveal
its serrated edge, and several reddish, irregular longitudinal stripes.
The Begonia studied here appears to
grow from a unique root structure that looks like a large tuber called
a caudex. The plant’s
stems grow from this caudex, which is half beneath the soil, and half
above. The visible portions of several of these root structures
can be seen below. Multiple stems originate from each
caudex. Notice the strange ribbon-like hairs that grow profusely
from the bases of stems.
Several additional ground level
views of the plant can be seen below. Notice in the first image
that the green surface of the caudex is covered with irregular brown
scales that are loosely attached. During hard times, the plant
can lose all of its foliage until nothing remains but the caudex.
When conditions improve, the plant is able to regrow stems, leaves, and
Three views of stems follow that
show their pale yellowish-green colouration, and tiny bright red
spots. The length of the stem’s irregular, ribbon-like hairs
decreases as one moves up the stem. Similar rough-looking hairs
appear to grow from both upper and lower leaf surfaces.
Closer views of the surface of a
lower stem reveal the structure of these strange hairs. Many are
quite long, and have apparently dried out to become thread-like near
their tips. It’s interesting to note that all of the hairs
originate from the bright red, irregularly shaped spots on the stem’s
Upper stems appear to be divided
into bamboo-like sections by raised rings. Notice how the stem’s
colouration, number and intensity of spots, and hair length
changes above the ring shown in the second image.
Here are a couple of images showing
bud-stage Begonia flowers. In each bud the two tepals are closed
like the two sections of a clam. If you examine the images very
carefully, you may be able see that some buds are attached to a green
base, while others are not. I wonder what this means?
The answer of course, is that some
of the buds are pistillate, and some are staminate. The two seen
at the bottom of the image on the left below are pistillate, as
evidenced by their light green ovaries. The bud at the top of the
image (which is seen close-up in the right hand photograph), is
Still closer views of this male bud
can be seen below. Notice that both its tepals, and its stalk are
covered with bulbous-tipped glandular hairs. Most hairs emanate
from the red spots on a surface.
As you can see below, the stalks of
both male and female buds may grow from the same junction on the stem.
Additional views of glandular hairs
follow. Note in the left image, the two tiny leaflets that join
the stalk just beneath a bud.
Two images can be seen below that
reveal pistillate buds in the process of blooming.
When fully open, the two tepals
that form the flower’s combined calyx-corolla are positioned almost in
Let’s now take a closer look at the
male staminate flowers of the Begonia. In terms of the flower’s
tepals, they are identical to pistillate ones. However in this
case there is a cluster of stamens at the flower’s centre. In
this particular species, the stamens are grouped in an asymmetric, (or
zygomorphic) mass that resembles a bunch of bananas.
Higher magnification shows that
each bright yellow anther is supported by a short, pale yellow-green
A view from above the group of
stamens shows how tightly they are packed side by side in the cluster.
Front and side views of a cluster
reveal that all stamens have a similar curvature.
Now let’s look more closely at
pistillate flowers. Here there are three bright yellow stigmas,
each with two lobes at its tip.
Much higher magnification reveals
that the surface of each bi-lobed stigma is entirely covered by fine
hairs that increase its surface area, and thus help to acquire, and
retain pollen grains. Notice also that the styles supporting
stigmas are stocky and curved.
A side view of a female flower
shows clearly that the three pistils are connected to an impressively
large, light green ovary which possesses three thin, but broad, lighter
coloured ‘wings’. (The third wing is not visible in the
Begonias are noted for their
asymmetric leaves. The upper surface of one such leaf which has
8, pointed, serrated lobes is shown below. The image on the right
shows the strange bright red ‘beard’ composed of coarse hairs that
grows from the point of connection of the stalk to the leaf.
A view from beneath the same leaf
shows that its underside has a bright red colouration! The image
on the right shows a different view of the ‘beard’ mentioned above.
More highly magnified views of the
underside of a leaf can be seen below. Notice the many hairs that
grow from the leaf’s surface, and edge. Begonia leaves contain
the chemical calcium oxalate within their cells, which makes them
poisonous to animals.
The approximately 1500 species of
wild Begonias grow in a wide variety of ecological niches, most in
tropical and sub-tropical regions. Only one tropical region is
without native species, and that is Australia!
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
A Flower Garden of
A complete graphical index of all
of my flower articles can be found here.
The Colourful World of
A complete graphical index of all
of my crystal articles can be found here.
Microscopy UK or their contributors.
Published in the July
2011 edition of Micscape.
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