Close-up View of the
by Brian Johnston (Canada)
...their mornings were of silver,
their evenings were of gold,
the berries never fell,
the Silverberry Tree.
This very common tree, (or more properly, shrub), is referred to as the
“Silverberry”, “American Silverberry”, Wild Olive” or “Wolf
Willow”. Native to Eastern Canada and parts of the United States,
the Silverberry is unique because of the distinctive silvery appearance
of its leaves, young bark, flowers and fruit. It grows weed-like,
in almost any location. This is probably due to its extreme
tolerance of dry locations, and its ability to “fix” nitrogen
from the atmosphere. In fact, the tree’s presence in a given
location enhances the growth of the surrounding grasses.
The genus name Elaeagnus is
derived from the Greek “elaia”,
meaning olive, and “agnos”,
referring to the Chaste Tree, which has similar foliage. Commutata, the species name, means
changed, and was given to the plant because the silvery foliage has a
‘changed’ colour, from the more common green of other plants.
Two examples of Silverberry trees, photographed in early spring, can be
seen below. The one on the right exhibits some frost damage to
the lower branches.
A closer view of the tree reveals that only the new-growth branches are
the distinctive silvery colour. Old-growth branches have an
attractive red-brown colour. Notice in the image on the right,
the light silvery colouration of the foliage, contrasting with the
darker grasses in the background.
During the months of June and July, yellow, fragrant flowers bloom in
profusion along the new-growth shoots. These flowers open in
order from the shoot’s base to its tip.
Notice in the image that follows, that the buds have the characteristic
silvery colour of much of the rest of the plant. Also notice the
dramatic difference in colouration of new and old-growth.
Newly opened Silverberry flowers display their silvery exterior, and
yellowish interior. Although a flower appears to have four
pointed petals, it does not! The “petals” are in fact sepals (modified leaves). The
photograph shows clearly the strange texture of the outer surfaces of
these sepals. It almost looks as if someone has sprayed on a coat
of silvery ‘flock’!
The spreading sepals of mature flowers enclose the reproductive organs
– four yellow stamens, and a single light-green pistil.
Unlike the consistently shaped pistil of most other flowers,
Silverberry’s pistils show a variety of shapes.
A closer view of the flowers reveals these structures in more
detail. In the left image, notice that the silvery appearance of
leaves is due to their green surfaces being obscured by a multitude of
short, white or silvery-gray hairs.
Each flower is connected to the new-growth branch by a short
stalk. Notice the rough texture of the fused-sepal base of the
Under the microscope, the remarkable structures that produce this
texture are visible. Many circular, flat, disk-like wheels with
spiked edges, are packed randomly in layers over the sepal’s external
surface. Who would have thought!!
The anthers (male pollen producing structures) of a flower are yellow,
or brown. The filaments that support the anthers are not visible
in the photographs, as they are hidden within the fused sepal base of
Photomicrographs showing the surface of an anther can be seen
below. The pollen grains that coat the surface are tri-cornered.
At the centre of the four stamens is the pale, yellow-green stigma
(female pollen accepting organ), and its supporting style. The
image on the right shows that the stigma usually extends beyond the
ring of anthers.
A tubular, curved stigma is shown in the photomicrograph that follows.
Curving, pollen encrusted styles can be seen in the images that follow.
The shape of Elaeagnus commutata
pollen grains can be seen in the dark-ground image on the left, and the
higher magnification phase-contrast image on the right.
The upper, (left), and lower, (right), surfaces of Silverberry leaves
can be seen below. Each leaf is concave on its upper surface, and
convex on its lower surface.
A low magnification photomicrograph of a leaf’s upper surface is shown
below. The surface’s structure is difficult to see at this
Higher magnification reveals (surprise!) that the same disk-like
structures seen on the flower’s sepals are also present on the
leaf. (I wonder what the unusual banded, ribbon-like structure is
that can be seen at the centre of the left image??)
After the flowers have completed blooming, small ellipsoidal fruit
resembling a dry, mealy, whitish berries begin to increase in size.
Eventually these berries (which contain a hard stone), grow to about
1.5 centimetres in length. A botanist would refer to each fruit
as a “mealy, drupe-like achene densely covered by a silvery gray
pubescence”. (A drupe is a
fleshy fruit with a central stone-like core containing one or more
seeds. An achene is a
small, dry, seedlike fruit with a thin wall that doesn’t open.)
Although birds and other small mammals help to disperse the plant’s
seeds, in cold climates another dispersal mechanism occurs. In
the winter, the wind blows the seeds across the frozen hard-packed
surface of the snow! (In my view, this may be the ONLY positive thing that can be said
All of 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.
Little, Elbert L. National Audubon Society Field Guide to North
American Trees - Eastern Region. 2004. Alfred A. Knopf, Inc.
(Chanticleer Press, Inc. New York)
A Flower Garden of
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.
Microscopy UK or their contributors.
Published in the August
2008 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 .