When the names of nearly 3,000 September 11 victims are read aloud Wednesday at the World Trade Center, a half-dozen stacks of stone will quietly salute an untold number of people who aren't on the list.

The granite slabs were installed on the memorial plaza this spring. They recognise an initially unseen toll of the 2001 terrorist attacks: firefighters, police and others who died or fell ill after exposure to toxins unleashed in the wreckage. The unusual addition reflects a memorial that is evolving as the aftermath of 9/11 does. And for families like Joanna Reisman's, the new 9/11 Memorial Glade gives their loved ones a place in the landscape of remembrance at ground zero.