Close up view of the wildflower corn speedwell

Yellow and white wildflowers are extremely common, and when one finds the much rarer, attractive blue-violet blooms seen in the image above, it is worth taking a closer look. This is particularly true since the plant doesn’t last very long after flowering. In fact, it is one of the earliest bloomers in the spring, and soon becomes obscured by the grasses and other weeds that grow much taller. The plant photographed for this article had already been partially hidden by long grass on a hillside, but a hint of blue indicated its presence a moment before I would have crushed it underfoot.

Veronica arvensis is an annual, native to Europe, that normally grows in the form of a tangled mat over the surface of the ground. If nearby plants compete with it for sunlight, it grows upright stalks that can be up to 25 cm high. (My plant was approximately 10 cm in height.) Near the ground, the main stems branch into many side stems, however the side stems themselves are mainly unbranched. Fine hairs cover most stems.

The common name “Speedwell” was chosen to reflect the speed with which the plants spread. The species name arvensis is derived from the Latin for “belonging to the plowed land”, and refers to its presence in lawns and gardens.

As can be seen below, the plant’s flowers have four rounded petals, with one being slightly smaller than the others. The flowers are incredibly small – less than 5 mm in diameter! The corolla, a structure formed by the petals, is a blue-violet colour which becomes white at the “throat” where the petals are fused into a tubular base. Darker, blue-violet lines radiate out from the flower’s centre. They are thought to function as nectar guides to visiting insects.

Closer views of a flower show its reproductive structures. Emanating from the throat is a single pistil, and two stamens. In most flowers, these structures have approximately the same length.

Notice the fragile style, and the much sturdier filaments.

Although the anthers, (male pollen producing organs), are actually blue in colour, this is difficult to see because of their coating of white pollen grains.

Under the microscope however, the striking blue colour of the anther is revealed.

Higher magnification shows the ellipsoidal, or egg-shape, of each pollen grain.

Phase-contrast illumination, and a still higher magnification, reveal that a grain has several longitudinal grooves on its surface.

The following two images show the surface structure of the stocky filament that supports the anther.

A flower’s pistil consists of a thin white style and bulbous, white stigma (female pollen accepting organ).

These two structures can be seen more clearly in the two photomicrographs that follow. Notice the long, hair-like protuberances that help collect, and retain pollen grains like the one seen in the image on the right.

If a section of a Corn Speedwell petal is removed from the flower, and examined under the microscope, its variable blue pigmentation, and cellular structure are visible. Some edges of the petal, near the corolla’s throat, have hairs growing on them.

At the very base of the corolla tube, the structure is green in colour due to the presence of chlorophyll. Many hairs are also present in this location.

Cool springtime temperatures can result in what are called “infestations” of this tiny plant. In my opinion, a patch of Corn Speedwell is better referred to as a visual “treasure”.

Photographic Equipment

The photographs in the article were taken with 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. 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.

The photomicrographs were taken with a Leitz SM-Pol microscope (using dark-ground and phase-contrast condensers), and the Coolpix 4500.

References

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.

A Flower Garden of Macroscopic Delights

A complete graphical index of all of my flower articles can be found here.

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A complete graphical index of all of my crystal articles can be found here.

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