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Wild cucumber is known by many names, some of which are: prickly cucumber, wild balsam apple, balsam apple, creeping jenny, four-seeded bur cucumber and concombre grimpant. It exists throughout North America as a trailing vine that can be up to six metres long. The plant grows from an underground tuber that can weigh up to 50 kilograms!

Both locations that I used to obtain specimens, (over a two year period), were near the banks of streams or rivers. Wild cucumber normally uses branched tendrils to climb shrubs and trees, but some plants simply trail along the ground.

Botanically speaking, the plant is a member of the gourd or cucurbitaceae family. The genus name Echinocystis is derived from the Greek words echinos, meaning “hedgehog” and kustis meaning “bladder”. These terms refer to the shape of the fruit, one of which can be seen above.

The two images below show a typical plant. The large leaves that can be seen in the second photograph are alternate, and attached to the stem by long stalks. Each leaf is palmately shaped, and has five pointed lobes. At the junction of the leaf stem and the main stem, (the leaf axil), a long string of flowers, (called a panicle) is attached. All but one of the flowers in a panicle are male. The one female flower is located at the leaf axil.

As mentioned earlier, the wild cucumber stem is supported by many curled tendrils which occur in groups of three, and are attached opposite to each leaf axil. The strength of these tendrils is amazing. As can be seen below, it was sometimes easier to cut the supporting stem, when trying to pull the wild cucumber plant away from its environment!

The tip of a single panicle, with its many male flowers, is shown in the image that follows.

Each smaller branch emanating from the main panicle stem holds a group of flowers. Several examples are shown below.

The male flower is white, with a green center, and has six petals which curve up to form a shallow bowl shape. Most flowers are 8 to 16 mm in diameter.

At the center of the flower is a single stamen consisting of a green supporting filament and yellow anther (male pollen producing organ). If you look closely, the tip of each petal appears to be covered in fine white hairs.

Under the microscope, (using dark-ground illumination), the structure of a petal tip is visible. The cells appear to be transparent, and the petal is covered with glandular (round-tipped) protuberances.

A higher magnification reveals more details of these protuberances. The gland at the top of the right-hand image appears segmented.

The colour of the petals transitions from white to green at the center of the flower. Notice the tiny, green, needle-like sepals (modified leaves) that are visible between the petals.

Several glandular structures can be seen projecting from the green area.

A photomicrograph of the filament supporting the anther reveals many ellipsoidal pollen grains with longitudinal grooves.

Growing at the base of each panicle of flowers, with its stalk attached to a leaf axil, the female flower is distinguished by its spherical, spiked ovary. Since the ovary is beneath the petals, it is referred to as “inferior”.

After fertilization, the ovary begins its transformation into the fruit of the wild cucumber.

In the image on the left below, the remnants of the single stigma, (the female pollen accepting organ), is visible at the bottom of the fruit. The image on the right shows the sharp prickles that emanate from the fruit’s surface.

It is difficult not to stand and stare when one comes upon a late-stage fruiting wild cucumber vine. The many pendulous green ellipsoids are quite striking.

The mature fruit shown in the two following images was about 5 cm long. The prickles are relatively weak, and bend rather than penetrate the skin when the fruit is handled.

Two close-ups of plant structures follow. The first image shows a corkscrew-like tendril, while the second shows mature prickles, which have turned from green to yellow at this late stage of development.

The longitudinal cross-section through the fruit shows two of the four seeds. (There are two more “behind” the two shown.) Most of the fruit is composed of fleshy greenish-white material.

A transverse cross-section reveals the position of all four seeds. Notice the darker outer capsule, beige inner tissue, and empty space at the center of each seed.

About a month after the earlier fruit had been picked and photographed, I returned to the same location and removed several, now dried fruit shells. The outer structure is now light brown, and an interesting inner seed-protecting webbed structure can be seen. The right image shows that all four seeds exit through the two oval openings in this inner protective chamber. In fact, if you look closely, you may be able to see one dark brown seed still in position deep within the left-hand chamber.

With much shaking, I was able to dislodge one of the flat, oval, seeds. Normally as the shell dries out, and begins to break apart, gravity causes the seeds to fall to the ground.

To get a better view of the interestingly patterned inner structure, I cut open the outer layer with scissors. The structure is a marvel of engineering! It is not only extremely strong, but appears to be waterproof as well!

This strange wildflower is not very abundant in the area where I live in Toronto. When I first found the plant, there were perhaps four or five examples growing up the trunks of trees near a stream. One year later, during the hottest summer on record, there was not a single plant to be found in the same area! Since I still needed some additional photographs to complete this article, I was forced to look elsewhere. Fortunately, while visiting my parents who live about 100 km away, I found a huge number of plants growing beside the river which runs through the town. The year before there had been almost none! Such are the vagaries of plant growth!

Photographic Equipment

An eight megapixel Sony CyberShot DSC-F 828 equipped with achromatic close-up lenses, (Nikon 5T, 6T, Sony VCL-M3358, and shorter focal length achromat used singly or in combination), was used to take most of the macro images. The lenses screw into the 58 mm filter threads of the camera lens. Still higher magnifications were obtained by using a macro coupler (which has two male threads) to attach a reversed 50 mm focal length f 1.4 Olympus SLR lens to the F 828. A few of the photographs in the article were taken with an eight megapixel Canon 20D DSLR and Canon EF 100 mm f 2.8 Macro lens. ( The images were photographed over two summers.) The photomicrographs were taken with a Leitz SM-Pol microscope (using a dark-ground condenser), and a Nikon Coolpix 4500 camera.

References

The following references have been found to be valuable in the identification of wildflowers, and they are also a good source of information about them.

Dickinson, Timothy, et al. 2004. The ROM Field Guide to Wildflowers of Ontario. Royal Ontario Museum & McClelland and Stewart Ltd, Toronto, Canada.

Thieret, John W. et al. National Audubon Society Field Guide to North American Wildflowers - Eastern Region. 2002. Alfred A. Knopf, Inc. (Chanticleer Press, Inc. New York)

Kershaw, Linda. 2002. Ontario Wildflowers. Lone Pine Publishing, Edmonton, Alberta,Canada.

Royer, France and Dickinson, Richard. 1999. Weeds of Canada. University of Alberta Press and Lone Pine Publishing, Edmonton, Alberta, Canada.

Crockett, Lawrence, J. 2003. A Field Guide to Weeds (Based on Wildly Successful Plants, 1977) Sterling Publishing Company, Inc. New York, NY.

Mathews, Schuyler F. 2003. A Field Guide to Wildflowers (Adapted from Field Book of American Wildflowers, 1902), Sterling Publishing Company, Inc. New York, NY.

Barker, Joan. 2004. The Encyclopedia of North American Wildflowers. Parragon Publishing, Bath, UK.

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