1. (Science: botany) An aquatic plant of the genus Sagittaria, especially. S. Sagittifolia, named from the shape of the leaves.
2. (Science: cell biology) fanciful description given to the pattern of myosin molecules attached to a filament of f actin. Easier to see if tannic acid is added to the fixative. The arrowheads indicate the polarity of the filament, the barbed (attachment) end is the site of major subunit addition.