Stamens and Pistils 102

by Ernie Bernard

If you've read the previous Fun Fact on stamens and pistils you may be ready to read more about how they work. For illustration, we'll study one of the park's more common and strikingly colorful wildflowers - the western wallflower (Erysimum capitatum). A member of the mustard family (Brassicaceae), it is found throughout the park.

The western wallflower is large enough to show its major reproductive parts without benefit of microscopic examination through a hand lens, but a small 10x lens is always convenient to have in the field.

Of the four parts that make up a typical flower, we're still concerned with stamens and pistils. The other two parts - sepals and petals - the ones that catch our eye, are termed accessories, perhaps granting a broader understanding of what it means for a person to "accessorize."

The stamens surround the pistil. Stamens produce the pollen or male gamete (sex cell) that will fertilize ova (eggs) inside the pistil. To further complicate things a bit, the pistil consists of several parts, but the most significant in this study is the ovary, which as one would expect holds ova (eggs). Some plants can fertilize themselves while others can't. But since heterogeneity (a posh but nicely precise word for diversity) is good in nature, there are built-in devices to promote cross-pollination, i.e. one plant's pollen will fertilize the ova on a different plant. Wind is one way to do this, as anyone in Rocky Mountain National Park in early June can see. As spring turns to summer, huge yellow clouds of pine pollen waft across the green slopes and ridges.

Animals are a most effective way to transfer pollen. Many flowering plants have evolved complex adaptations that assist in pollination by animals. Some flowers produce an odor like dung or rotting flesh to attract flies. Others - more to our liking - produce sweet scents, bright colors, or even colors in the ultraviolet spectrum that can be seen by the honeybee but not humans.