The Pinewood Morris Men continue a festive dance style from the late middle ages in rural England. The performers wear costumes specific to their troupe, including bells, and often wield sticks or handkerchiefs in their routines. This group frequently appears in Boston Revels’ events throughout the year. Here they are greeting concertgoers to last fall’s equinox RiverSing in the Herter Park amphitheater along the Charles River in Allston.