My column today is about fake grass, and the virtues of going back to California's natural -- brown -- roots to save water and spare ourselves the golf-course-in-your-front-yard esthetic.

   Stuart Gaffin, the Columbia University researcher I talked to about artificial turf, is working on a project that's worth sharing: living roofs.

    Roofs are an enormous heat source in cities, and Gaffin is proposing covering Big Apple rooftops in a thin layer of lightweight soil and planting certain succulents to cool off the city. Here's the website to take a look at the experiment:

http://128.59.83.19:81/command=RTMC&screen=Weather%20Station%20Fieldston%20School%20(FS)

    If this works, maybe the next step could be ... grazing, like the critter in Jean Cocteau's farce ``The Ox on the Roof,'' or a Marc Chagall cow, no longer floating but lunching and munching on some rooftop greenery.