The Riverway keeps a green seam between Brookline and Boston, and AMR Landscape Associates works the yards on either side of it. Mowing starts early here, while mist is still lifting off the Muddy River and the sycamores hold the last cool air of the night. Lawns in this part of town are small and hemmed in by stone and shade, which makes an even cut and a clean border worth the extra pass. By the time traffic thickens on Brookline Avenue, the strips of grass out front are striped and swept and the clippings are gone. It is ordinary work, and it makes a whole street look cared for.