Seago & SeagoWe examined plants with 5 or 6 stem segments, including fertile synangium branches in terminal segments, with various staining and microscopic methods to demonstrate Casparian bands of an endodermis in the whisk fern, Psilotum nudum. We began most visual examination with fresh, unstained sections viewed under brightfield and then epifluorescence, followed by staining stem sections with berberine hemisulfate, that were viewed epilfuorescently and then counter-stained with aniline blue, gentian violet, or toluidine blue O. Specimens were also stained in fluorol yellow and viewed in epifluorescence, or in phloroglucinol HCl, Sudan red 7B, or Sudan IV under brightfield and often epifluorescence. The occurrence of an endodermis with Casparian bands in the stems of Psilotum nudum is demonstrated from the plant’s rhizome below ground to all above ground stem segments through 4 or 5 bifurcations or dichotomies.