Gratiot Boulevard runs the length of Marysville, and by late April the lawns on either side of it have shaken off winter and turned that first startling green. RJR LAWN SERVICE starts its rotation right about then — mowing, trimming, edging drives and sidewalks so the season begins on a definite line. Through summer it is a matter of keeping up, because grass this close to the water does not ease off until September. Then the work shifts to plowing, driveways and approaches cut open after a night of blowing snow off the channel. Between the riverfront and the western townships, that is the loop.