Fraxinus spp.; ash [Oleaceae]  Medium to tall trees with opposite compound leaves of typically 7 to 13 leaflets.  Long and narrow fruits with a single terminal wing are released late in the year, and are often blown long distances over the ice of rivers and lakes during the winter.  Most species have large, half-round, notched leaf scars, showing an elliptical line of tiny, vascular bundle scars.  Wisconsin species include:  F. Americana (white ash), which grows tall in fertile, well drained woods; F. Pennsylvania (green ash), most common in moist habitats but widely planted elsewhere; and F. nigra (black ash), which is typical of hardwood swamps.  [120]