Close-up View of the
by Brian Johnston (Canada)
caprea has buds that open in spring before the plant’s leaves
make an appearance. These furry buds, the ‘pussies’ in the name
pussy willow, are referred to as catkins.
All willows are dioecious,
meaning that male and female flowers occur on separate plants. In
this article, only the more ornamental male flowers have been
photographed. Salix caprea
is sometimes referred to as goat willow, pink willow, or florist’s
The image above shows a group of male catkins at different
developmental stages. The pinkish orange colour of the small
catkins on the right eventually fades to a light green colour.
Notice that the buds are initially protected by shiny, brown,
beetle-shaped structures that fall away as the catkins grow larger.
Compare the branch with blooming catkins on the right, with one about a
week before blooming on the left. (The yellow structures
connected to the catkin by thin filaments are the anthers of individual
flowers within the catkin.)
Each male catkin is intensely hairy, and these hairs all but obscure
the black tips of the bracts
(modified leaves) that are associated with each flower.
At the growing tip of a willow branch, three very tiny catkins are
completely enclosed by hairy green bracts that in turn, grow out from
under brown protective covers. Note that the brown cover becomes
less hairy as time progresses.
Under the microscope, the number of hairs growing from one of the
bracts is amazing. One must focus through the hairs to visualize
the cellular structure beneath (right image).
Higher magnification gives a better view of the bract’s hairs.
The two views below show a very immature catkin with its almost
completely pink colouration. At this point the protective cover
will detach by the action of the wind or other vibration.
As the catkin matures, the pinkish-orange colour is restricted to the
top portion, and a light green colouration creeps up from the base.
The higher magnification used in the three images that follow reveals
that the pinkish-orange colouration is due mainly to the triangular
bracts associated with the flowers that make up the flower-head.
Eventually, the black-spotted, light green colour is uniformly
distributed over the surface of the catkin.
A photomicrograph of a tip of one of the black bracts is shown in the
In the previous macro-photographs, one must deliberately focus deeper
into the catkin (using manual focus), in order to see the black
bracts. The camera’s auto-focus, if left to its own devices, will
always choose to focus on the closest plane, which in this case is the
shroud of fine hairs cocooning the catkin.
If one dissects a catkin by lifting away the overlying bracts, inner
structures are revealed.
On the left are two filaments
that support anthers (the male
pollen producing organs). (Each individual flower in the catkin
has two stamens.) Notice the interesting shape of the hairs that
grow near each filament’s base.) The right-hand image shows
several immature anthers buried beneath the layer of black bracts.
The point of attachment of an anther to its supporting filament can be
Finally, the catkins begin to bloom, usually in order from the top of
the branch to the bottom of the branch. In contrast, each
individual catkin blooms from bottom to top.
Once the catkins begin to bloom, leaves begin to sprout along the
length of the twig. These too grow out from under brown
Just below the centre of the image at left below, notice the scar that
is left after one of the protective covers falls off. The image
at right shows one of the covers being pushed away from the stem by the
emerging hairy leaflet.
Here is a closer view of one of the distinctive scars.
If you look carefully at the image below, you can see the yellow tips
of anthers pushing out from under the black bracts in the area near the
middle of the catkin.
Higher magnification gives a better view of the process.
Notice in the image that follows, that the stamens may have different
lengths on different sides of the catkin, resulting in a
The mature anthers are banana-yellow in colour. Notice the white
supporting filaments in several of the images.
Each anther appears to be divided into four lobes.
Under the microscope an anther with several attached pollen grains
(left), and a supporting filament (right), can be seen.
Higher magnification reveals the ‘bent’ ellipsoidal shape of pollen
As a catkin ages, the anthers begin to shrink to a fraction of their
During the dissection of a mature catkin, copious sticky nectar coats
the fingers. This nectar attracts bees and other insects to the
plant, and when they fly to another female tree, fertilization is
Most of us, I‘m sure, have seen pussy willow catkins in early
spring. I hope that the images in this article have given you a
greater appreciation of these unique and striking structures.
Most 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.
A few photographs were taken with an eight megapixel Sony CyberShot
DSC-F 828 equipped with achromatic close-up lenses (Canon 250D, Nikon
5T, 6T, Sony VCL-M3358, and shorter focal length achromat) used singly
or in combination. The lenses screw into the 58 mm filter threads of
the camera lens.
The photomicrographs were taken with a Leitz SM-Pol microscope (using a
dark ground condenser), and the Coolpix 4500.
Microscopy UK or their contributors.
Published in the
September 2007 edition of Micscape.
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