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I remember as a child, reading the true story of Jonathan Chapman (1774-1845), also known as “Johnny Appleseed”, and his travels throughout the United States over a period of fifty years in order to distribute apple seeds to people he met along the way. The story gave “Johnny” much of the credit for the abundance of wild apple trees in many American states.

The subject of this article is not a descendant of one of those trees; (he didn’t cross the border to Canada), but it is the same species, Malus sylvestris. My wild apple tree grows next to the bank of a small stream near my home. For much of the year it looks unkempt, wild and straggly. In early spring however, a transformation takes place, and the tree is literally smothered in beautiful white blossoms like those shown above.

A few days earlier, the tip of the same branch had buds and partially opened flowers. I was surprised to find that a branch of flowers, when cut and placed in water, continues to grow for more than a week. This meant that I didn’t have to keep cutting new samples from the tree to use as photographic subjects.

Notice below, the early leaves that have not opened fully. The pinkish hue slowly fades to light green as time passes. Strangely, the leaves emerge from a ring of green sepals (modified leaves).

The images below show that the stems of the buds and blossoms also grow from a similar ring of sepals that is right at the bark level. From one to four or five stems can emerge from a single sepal ring. Twigs are reddish-brown in colour, but tend to become grayer later in the season.

Immature sepals are quite curved, and have many sharp, pointed serrations along their edges.

The developing buds are completely white in colour, and have a ring of five light green sepals clasping them. Between the bud and stem is a bulbous growth-the ovary (the organ that develops into the fruit). In several of the images, you may notice a hint of the bright yellow anthers within the bud.

Flowers in various stages of opening are shown in the image that follows.

Although wild apple blossoms are not colourful, they are nevertheless striking!

A closer look at a blossom shows the details of its reproductive structures. A single pale green pistil, composed of a cylindrical style supporting a bulbous stigma, (the female pollen accepting organ), is surrounded by many stamens, composed of thin white filaments topped by bright yellow anthers, (the male pollen producing organs).

Up to about twenty stamens surround the pistil in a given flower. Each anther is usually encrusted with pollen grains.

Strangely, there are no pollen grains on the surface of the anther shown in the photomicrograph on the left below. Another anther, shown with higher magnification, has a few ellipsoidal grains stuck to its surface.

This anther has many pollen grains attached, and the longitudinal groove on each grain is clearly visible.

The supporting filament is composed of many long, tightly packed rectangular cells.

The single pale green pistil in each flower is about the same length as the anthers.

With the flower’s petals removed, it is easier to see the distinctively shaped stigma at the tip of the style.

The stigma is almost perfectly heart-shaped. A photomicrographic side view of the stigma shows the many blunt protuberances that capture pollen provided by insect visitors - mainly honeybees. A wild apple flower is “self-sterile”, and since the flower’s own pollen cannot fertilize it, insects are essential.

Once a flower has been successfully fertilized by an insect, the ovary swells, and the transformation into an apple begins. Using proper botanical terminology, the fruit is more accurately called a “pome”.

Several weeks later, the pome has become a recognizable apple. In the fall the apples from the tree are a mottled greenish-red, and have a maximum diameter of approximately three and a half centimetres.

It is strange that the seeds and leaves of the wild apple contain minute traces of the deadly poison hydrogen cyanide. Fortunately for apple lovers, the fruit is missing this unpleasant compound, for as the saying goes:

“An apple a day keeps the doctor away!”

Photographic Equipment

About a third 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. An eight megapixel Sony CyberShot DSC-F 828 equipped with achromatic close-up lenses (Canon 250D, Nikon 6T, Sony VCL-M3358, and shorter focal length achromat used singly, or in combination), was used to take the majority of the 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. The photomicrographs were taken with a Leitz SM-Pol microscope (using dark-ground condenser), and the Coolpix 4500.

Reference

The following reference has been found to be valuable in the identification of trees, and it is also a good source of information about them.

Little, Elbert L. National Audubon Society Field Guide to North American Trees - Eastern Region. 2004. Alfred A. Knopf, Inc. (Chanticleer Press, Inc. New York)

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© Microscopy UK or their contributors.

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