A close up view of a Protea: Protea mundii
of a "Protea"
by Brian Johnston (Canada)
The origins of the unusual family of
flowers called the proteas are unknown. They are native to
Australia and southern Africa, and seem very strange to those of us
accustomed to dandelions and thistles. Botanists sometimes refer
to them as distant relatives of the Mistletoe family, although this
relationship has been called into question. Most agree however,
that proteas evolved early in the development of flowering
plants. They were perhaps evolution’s early experiments with
Members of the protea family (Proteaceae)
shrubs or trees with hard, leathery leaves that snap rather
than fold when bent (sclerophyllous).
blooms look like flowers, they are actually
flower-heads that contain many small individual flowers. These
flowers are enclosed within a cup (called the involucre), formed by overlapping
colourful bracts (modified
leaves). The term involucre is French, and is derived from the
Latin involucrum meaning a wrapper or envelope. The
bracts (brown and pink in the image above), overlap like the shingles
on a roof, and are therefore referred to as imbricate.
Notice in the first image in the article, and the one that follows, the
contrast between the intensely hairy pink and brown bracts, and the
hairless leaves. The bracts are covered by what best could be
described as “peach fuzz”, which increases in length and density near
A slightly higher magnification shows that the coverage of the hairs is
not complete. There are seemingly random sections where the
density is diminished.
Many of the intermediate and upper pink bracts have brown tips.
Notice the unusual patterns formed by the hairs in the images below.
Only the upper ring of more sharply pointed bracts have long tufts of
dense white hairs at their tips.
At the upper limits of normal macro-photography, individual hairs can
When examining a bract under the microscope, it is difficult to obtain
a clear photomicrograph of the hairs due to the extremely limited depth
of field. In the left image, one plane of hairs is in focus,
while in the image on the right, the bract’s surface is in focus.
Note the rounded triangular pollen grains visible in both images.
(Photoshop’s auto-level command was used to increase contrast in the
right image. This produces exaggerated colouration.)
The brown tips of bracts in the lower rings have an interesting
furrowed pattern on their surfaces.
This pattern can be seen more clearly in the images below.
The fan-shaped array of hairs at the tips of the topmost bracts can be
seen in the three images that follow, taken with increasing
Notice that the smooth round flower stalk becomes creased with furrows
just below the flower-head’s base.
To the naked eye, the lowest brown bracts look rather unsightly.
Up-close however, the pattern produced by furrows and hairs is quite
One of my pet peeves is the fact that many plant leaves have unsightly
blemishes caused by insects and disease. What a pleasure it is to
photograph the deep green leaves, and bright red stem of this
protea. They are as close to perfection as nature gets!
A front and side view of a leaf axil (point of attachment to the
stem), can be seen below. Notice the small hairy bump above the
axil, that is present for each leaf. If you look carefully at the
image at right you can see that even the stem is hirsute (hairy).
Two images showing the front surface of a leaf follow. The
surface is covered by tiny white specks. The photomicrograph on
the right shows a much higher magnification view of the leaf’s brown
edge (seen in the lower left corner of the left image). The
circular structures are the stoma
and guard cells that control
gas entry into the internal part of the leaf.
The back surface of the leaf shows more prominent veining, and the same
specks. The photomicrograph at right reveals these to be stoma
and guard cells.
A view down into the flower-head’s cup reveals a mass of needle-like
projections that are reproductive structures.
The two images that follow show the “pollen
presenters” of individual flowers located in the base of the
flower-head. These pollen presenters are actually pistils
composed of pollen encrusted styles which support tiny bulbous
stigmas. Since proteas are protandrous,
matures later than the anthers, thus reducing the chance of
Photomicrographs of the red stigma, and lower style can be seen
below. Notice that at this stage, pollen doesn’t adhere very well
to the tip of the stigma.
Many of the styles show the strange brown bumps that can be seen in the
images below. (Focus was adjusted between the two images to
highlight different details.)
Pollen grains clinging to the lower (left), and upper (right) portions
of the style can be seen below.
Higher magnification shows that each grain is roughly triangular in
The shape is easier to see in the still higher magnification
dark-ground image on the left, and phase-contrast image on the right.
These larger diameter structures can also be seen alongside the pollen
presenters. Each has a white tufted tip.
A photomicrograph of the tip follows.
Strangely, the structures above are actually tubes, which in time
disintegrate and fall away to reveal the pollen presenters seen
earlier! The images below show the stigma, and the top of the
For a more complete description of the details of protea fertilization
(with images), see my earlier
article on the pincushion protea.
The macro-photographs were taken with an eight megapixel Canon 20D DSLR
equipped with a Canon EF 100 mm f 2.8 Macro lens which focuses to
1:1. A Canon 250D achromatic close-up lens was used to obtain
higher magnifications in several images.
The photomicrographs were taken with a Leitz SM-Pol microscope (using
dark ground and phase-contrast condensers), and the Coolpix 4500.
Protea Atlas Project
All comments to the author Brian Johnston (firstname.lastname@example.org) are
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
2010 edition of Micscape.
Please report any Web problems or
offer general comments to the Micscape
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 .