Kind thanks to Ken McCown for this image of a nasturtium shared via the Botany Photo of the Day Flickr Group Pool (Flickr posting). This photograph was taken in the Huntington Botanical Gardens Herb Garden in California. As Ken mentions in his comments on Flickr, best seen at original size (warning, it's big!).
Unfortunately, I need to attach “tentative” alongside the name as it may be a cultivar that I'm not familiar with – there are nineteen cultivars listed in the RHS Plant Finder for Tropaeolum majus, after all. For a gardening perspective, read this article on nasturtium by Dr. William Welch of Texas A&M University.
The family Tropaeolaceae is monotypic, which, if you'll recall from an earlier entry, means that it contains only the one genus, Tropaeolum. It is distributed natively in the New World, from Mexico south to the southern tip of South America.
Botany resource link: Why the Banana Needs Protection via Jeremy Cherfas on the International Plant Genetic Resources Institute Public Awareness weblog. You may have seen media reports a few months ago about the impending extinction of bananas. As is most often the case, things are a little more nuanced than that.