1.   Another option being considered is building a makeshift boardwalk with large wooden mats plunked down atop the muck.

2.   But among most successful has been the conquest of the dreaded alligator weed, large mats of which had been choking the Everglades waterways.

3.   Going back up the brook in the dusk, I noticed that most of a large mat of watercress had been untouched by frost.