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Showing posts from May, 2009

Isotria verticillata (Orchidaceae)

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Three weeks ago, while on a field trip with the Missouri Native Plant Society, we stumbled upon a large population of Isotria verticillata at the peak of bloom. Anyone that has conducted surveys for rare, threatened or endangered species in the Midwestern and eastern United States has probably had this search image in their head (though maybe more so for its relative the federally threatened Isotria medeoloides).

Before I learned the vegetative field characters that distinguish this species from the often sympatric Medeola virginiana, I agonized over its identification. With practice and a visit to the herbarium, I learned they are quite distinct even when found in the sterile state. When sterile, both have a whorl of leaves at the top of the stem. However, Medeola has three (or sometimes five) distinct veins in each leaf while the venation of Isotria is inconspicuous and more reticulate. The venation of Isotria reminds me of the organization of juice sacks you find in an orange …