Botany Photo of the Day

I've covered most broadly-defined groups of plants on Botany Photo of the Day in the past two-plus years. However, here's a representative of one group that I've neglected to date, the gnetophytes.

Traditionally, seed-bearing plants were thought to be divided into two groups: the angiosperms (flowering plants with seeds developing within a carpel) and gymnosperms (non-flowering plants with seeds developing naked on the scale of a cone or equivalent). While the angiosperms remain a phylogenetically-sound group (i.e., all derived from a common ancestor), the gymnosperms are now thought to be an artifical grouping. In other words, we use the term gymnosperms for non-flowering seed-bearing plants because it is convenient to do so and not because it reflects a common-ancestor evolutionary relationship among the plant groups with those qualities.

The gnetophytes, including the genus Ephedra, are one of four groups traditionally thought of as gymnosperms (the other three being conifers, cycads and ginkgos). However, they differ from the other three groups in that they contain vessel elements, a cell type found in the water-conducting tissues. Interestingly, vessel elements are commonplace in the flowering plants. The presence of vessel elements in the gnetophytes has long been held up as one of the hints that the gymnosperms are an artifical grouping, with the corollary that the evolutionary relationships among the groups is more complex than it seems at first glance.

Ephedra is typically distributed across the northern hemisphere, but Ephedra frustillata is one of the exceptions. It is found in Tierra del Fuego as well as mainland Argentina and Chile (here's a photo of it in habitat). The macro photograph shows the pollen-producing male cones in detail (and they were producing heavily; the legs of my tripod were painted yellow after taking these images).